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  • Orienting ship movement in asteroids [closed]

    - by BadSniper
    Possible Duplicate: Move sprite in the direction it is facing? I'm programming asteroids game. I'm trying to give velocity in the direction of ship face. I've tried using velocity.x = velocity.x * cos r, velocity.y = velocity.y * sin r where velocity is a vector and r is the angle rotated. but it's not moving in right direction. Could someone help with this problem? It is supposed to return the vector in which ship is facing. I don't understand the problem.

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  • How to escape trailing backslash in NVelocity

    - by Ben
    I am using NVelocity to process various PowerShell scripts before they are executed against a server. My question is how to escape a backslash trailing a variable: e.g. ls \\$computername\c$ $computername should be replaced with a valid computer name at runtime, but the trailing backslash (\c$) means that it does not. Thanks Ben

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  • Caching Solutions

    - by dave
    Has anyone done a thorough comparison of AppFabric and NCache or AppFabric and ScaleOut? We are currently looking to implement either AppFabric, NCache or ScaleOut for distributed caching in geographically distant locations and I would like to know anyone's thoughts who has compared them side by side. I appreciate that many people use one or the other and tell me why their chosen solution is great but I am really looking for a comparison of the two products. Such things as what does AppFabric not do or not do well (if anything), partially from a features point of view but also from developer's point of view. Is working with one compared to the other nicer, easier, more flexible, more powerful, etc. There are plenty of lists of features which I can compare but am really looking for a comparison from someone who has perhaps been in a similar position to us and has performed the evaluation that we are about to launch into which will give us some food for thought whilst we do so. Thanks in advance.

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  • Create user variable in Intellij File Template

    - by Matt Broekhuis
    I am trying to use Intellij's file templates (not live templates) to help mitigate how much boilerplate code I use when making Services, daos, and their interfaces. I am able to use all the system defined variables just fine, such as ${PACKAGE_NAME} What I want though, is to be able to use my own variable names, like ${MY_USER_INPUT} however, when i do this like above, I get an error The documentation says : It is also possible to specify arbitrary number of custom variables in format ${<VARIABLE_NAME>}. and then Intellij is supposed to prompt the user for the value. However, this just plain doesn't work for me. What am I missing?

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  • Core Location and speed measurements

    - by Krumelur
    Does anyone know if Core Location in the iPhone OS uses anything but simple vector math to calculate speed? I've read that the GPS system can provide speed measurements that can be accurate when position is not (I believe using the Doppler shifts of the signals). I've tried and failed to see if the iPhone does this. The question is basically, does this data contain information or is it just convenience functions, using (filtered?) location data?

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  • Movement prediction for non-shooters

    - by ShadowChaser
    I'm working on an isometric 2D game with moderate-scale multiplayer, approximately 20-30 players connected at once to a persistent server. I've had some difficulty getting a good movement prediction implementation in place. Physics/Movement The game doesn't have a true physics implementation, but uses the basic principles to implement movement. Rather than continually polling input, state changes (ie/ mouse down/up/move events) are used to change the state of the character entity the player is controlling. The player's direction (ie/ north-east) is combined with a constant speed and turned into a true 3D vector - the entity's velocity. In the main game loop, "Update" is called before "Draw". The update logic triggers a "physics update task" that tracks all entities with a non-zero velocity uses very basic integration to change the entities position. For example: entity.Position += entity.Velocity.Scale(ElapsedTime.Seconds) (where "Seconds" is a floating point value, but the same approach would work for millisecond integer values). The key point is that no interpolation is used for movement - the rudimentary physics engine has no concept of a "previous state" or "current state", only a position and velocity. State Change and Update Packets When the velocity of the character entity the player is controlling changes, a "move avatar" packet is sent to the server containing the entity's action type (stand, walk, run), direction (north-east), and current position. This is different from how 3D first person games work. In a 3D game the velocity (direction) can change frame to frame as the player moves around. Sending every state change would effectively transmit a packet per frame, which would be too expensive. Instead, 3D games seem to ignore state changes and send "state update" packets on a fixed interval - say, every 80-150ms. Since speed and direction updates occur much less frequently in my game, I can get away with sending every state change. Although all of the physics simulations occur at the same speed and are deterministic, latency is still an issue. For that reason, I send out routine position update packets (similar to a 3D game) but much less frequently - right now every 250ms, but I suspect with good prediction I can easily boost it towards 500ms. The biggest problem is that I've now deviated from the norm - all other documentation, guides, and samples online send routine updates and interpolate between the two states. It seems incompatible with my architecture, and I need to come up with a better movement prediction algorithm that is closer to a (very basic) "networked physics" architecture. The server then receives the packet and determines the players speed from it's movement type based on a script (Is the player able to run? Get the player's running speed). Once it has the speed, it combines it with the direction to get a vector - the entity's velocity. Some cheat detection and basic validation occurs, and the entity on the server side is updated with the current velocity, direction, and position. Basic throttling is also performed to prevent players from flooding the server with movement requests. After updating its own entity, the server broadcasts an "avatar position update" packet to all other players within range. The position update packet is used to update the client side physics simulations (world state) of the remote clients and perform prediction and lag compensation. Prediction and Lag Compensation As mentioned above, clients are authoritative for their own position. Except in cases of cheating or anomalies, the client's avatar will never be repositioned by the server. No extrapolation ("move now and correct later") is required for the client's avatar - what the player sees is correct. However, some sort of extrapolation or interpolation is required for all remote entities that are moving. Some sort of prediction and/or lag-compensation is clearly required within the client's local simulation / physics engine. Problems I've been struggling with various algorithms, and have a number of questions and problems: Should I be extrapolating, interpolating, or both? My "gut feeling" is that I should be using pure extrapolation based on velocity. State change is received by the client, client computes a "predicted" velocity that compensates for lag, and the regular physics system does the rest. However, it feels at odds to all other sample code and articles - they all seem to store a number of states and perform interpolation without a physics engine. When a packet arrives, I've tried interpolating the packet's position with the packet's velocity over a fixed time period (say, 200ms). I then take the difference between the interpolated position and the current "error" position to compute a new vector and place that on the entity instead of the velocity that was sent. However, the assumption is that another packet will arrive in that time interval, and it's incredibly difficult to "guess" when the next packet will arrive - especially since they don't all arrive on fixed intervals (ie/ state changes as well). Is the concept fundamentally flawed, or is it correct but needs some fixes / adjustments? What happens when a remote player stops? I can immediately stop the entity, but it will be positioned in the "wrong" spot until it moves again. If I estimate a vector or try to interpolate, I have an issue because I don't store the previous state - the physics engine has no way to say "you need to stop after you reach position X". It simply understands a velocity, nothing more complex. I'm reluctant to add the "packet movement state" information to the entities or physics engine, since it violates basic design principles and bleeds network code across the rest of the game engine. What should happen when entities collide? There are three scenarios - the controlling player collides locally, two entities collide on the server during a position update, or a remote entity update collides on the local client. In all cases I'm uncertain how to handle the collision - aside from cheating, both states are "correct" but at different time periods. In the case of a remote entity it doesn't make sense to draw it walking through a wall, so I perform collision detection on the local client and cause it to "stop". Based on point #2 above, I might compute a "corrected vector" that continually tries to move the entity "through the wall" which will never succeed - the remote avatar is stuck there until the error gets too high and it "snaps" into position. How do games work around this?

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  • 3D Ball Physics Theory: collision response on ground and against walls?

    - by David
    I'm really struggling to get a strong grasp on how I should be handling collision response in a game engine I'm building around a 3D ball physics concept. Think Monkey Ball as an example of the type of gameplay. I am currently using sphere-to-sphere broad phase, then AABB to OBB testing (the final test I am using right now is one that checks if one of the 8 OBB points crosses the planes of the object it is testing against). This seems to work pretty well, and I am getting back: Plane that object is colliding against (with a point on the plane, the plane's normal, and the exact point of intersection. I've tried what feels like dozens of different high-level strategies for handling these collisions, without any real success. I think my biggest problem is understanding how to handle collisions against walls in the x-y axes (left/right, front/back), which I want to have elasticity, and the ground (z-axis) where I want an elastic reaction if the ball drops down, but then for it to eventually normalize and be kept "on the ground" (not go into the ground, but also not continue bouncing). Without kluging something together, I'm positive there is a good way to handle this, my theories just aren't getting me all the way there. For physics modeling and movement, I am trying to use a Euler based setup with each object maintaining a position (and destination position prior to collision detection), a velocity (which is added onto the position to determine the destination position), and an acceleration (which I use to store any player input being put on the ball, as well as gravity in the z coord). Starting from when I detect a collision, what is a good way to approach the response to get the expected behavior in all cases? Thanks in advance to anyone taking the time to assist... I am grateful for any pointers, and happy to post any additional info or code if it is useful. UPDATE Based on Steve H's and eBusiness' responses below, I have adapted my collision response to what makes a lot more sense now. It was close to right before, but I didn't have all the right pieces together at the right time! I have one problem left to solve, and that is what is causing the floor collision to hit every frame. Here's the collision response code I have now for the ball, then I'll describe the last bit I'm still struggling to understand. // if we are moving in the direction of the plane (against the normal)... if (m_velocity.dot(intersection.plane.normal) <= 0.0f) { float dampeningForce = 1.8f; // eventually create this value based on mass and acceleration // Calculate the projection velocity PVRTVec3 actingVelocity = m_velocity.project(intersection.plane.normal); m_velocity -= actingVelocity * dampeningForce; } // Clamp z-velocity to zero if we are within a certain threshold // -- NOTE: this was an experimental idea I had to solve the "jitter" bug I'll describe below float diff = 0.2f - abs(m_velocity.z); if (diff > 0.0f && diff <= 0.2f) { m_velocity.z = 0.0f; } // Take this object to its new destination position based on... // -- our pre-collision position + vector to the collision point + our new velocity after collision * time // -- remaining after the collision to finish the movement m_destPosition = m_position + intersection.diff + (m_velocity * intersection.tRemaining * GAMESTATE->dt); The above snippet is run after a collision is detected on the ball (collider) with a collidee (floor in this case). With a dampening force of 1.8f, the ball's reflected "upward" velocity will eventually be overcome by gravity, so the ball will essentially be stuck on the floor. THIS is the problem I have now... the collision code is running every frame (since the ball's z-velocity is constantly pushing it a collision with the floor below it). The ball is not technically stuck, I can move it around still, but the movement is really goofy because the velocity and position keep getting affected adversely by the above snippet. I was experimenting with an idea to clamp the z-velocity to zero if it was "close to zero", but this didn't do what I think... probably because the very next frame the ball gets a new gravity acceleration applied to its velocity regardless (which I think is good, right?). Collisions with walls are as they used to be and work very well. It's just this last bit of "stickiness" to deal with. The camera is constantly jittering up and down by extremely small fractions too when the ball is "at rest". I'll keep playing with it... I like puzzles like this, especially when I think I'm close. Any final ideas on what I could be doing wrong here? UPDATE 2 Good news - I discovered I should be subtracting the intersection.diff from the m_position (position prior to collision). The intersection.diff is my calculation of the difference in the vector of position to destPosition from the intersection point to the position. In this case, adding it was causing my ball to always go "up" just a little bit, causing the jitter. By subtracting it, and moving that clamper for the velocity.z when close to zero to being above the dot product (and changing the test from <= 0 to < 0), I now have the following: // Clamp z-velocity to zero if we are within a certain threshold float diff = 0.2f - abs(m_velocity.z); if (diff > 0.0f && diff <= 0.2f) { m_velocity.z = 0.0f; } // if we are moving in the direction of the plane (against the normal)... float dotprod = m_velocity.dot(intersection.plane.normal); if (dotprod < 0.0f) { float dampeningForce = 1.8f; // eventually create this value based on mass and acceleration? // Calculate the projection velocity PVRTVec3 actingVelocity = m_velocity.project(intersection.plane.normal); m_velocity -= actingVelocity * dampeningForce; } // Take this object to its new destination position based on... // -- our pre-collision position + vector to the collision point + our new velocity after collision * time // -- remaining after the collision to finish the movement m_destPosition = m_position - intersection.diff + (m_velocity * intersection.tRemaining * GAMESTATE->dt); UpdateWorldMatrix(m_destWorldMatrix, m_destOBB, m_destPosition, false); This is MUCH better. No jitter, and the ball now "rests" at the floor, while still bouncing off the floor and walls. The ONLY thing left is that the ball is now virtually "stuck". He can move but at a much slower rate, likely because the else of my dot product test is only letting the ball move at a rate multiplied against the tRemaining... I think this is a better solution than I had previously, but still somehow not the right idea. BTW, I'm trying to journal my progress through this problem for anyone else with a similar situation - hopefully it will serve as some help, as many similar posts have for me over the years.

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  • Help with Collision Resolution?

    - by Milo
    I'm trying to learn about physics by trying to make a simplified GTA 2 clone. My only problem is collision resolution. Everything else works great. I have a rigid body class and from there cars and a wheel class: class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private OBB2D predictionRect = new OBB2D(new Vector2D(), 1.0f, 1.0f, 0.0f); private float mass; private Vector2D deltaVec = new Vector2D(); private Vector2D v = new Vector2D(); //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; private Matrix mat = new Matrix(); private float[] Vector2Ds = new float[2]; private Vector2D tangent = new Vector2D(); private static Vector2D worldRelVec = new Vector2D(); private static Vector2D relWorldVec = new Vector2D(); private static Vector2D pointVelVec = new Vector2D(); public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; setLayer(LAYER_OBJECTS); } protected void rectChanged() { if(getWorld() != null) { getWorld().updateDynamic(this); } } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); predictionRect.set(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position, getWidth(), getHeight(), angle); rectChanged(); } public void setPredictionLocation(Vector2D position, float angle) { getPredictionRect().set(position, getWidth(), getHeight(), angle); } public void setPredictionCenter(Vector2D center) { getPredictionRect().moveTo(center); } public void setPredictionAngle(float angle) { predictionRect.setAngle(angle); } public Vector2D getPosition() { return getRect().getCenter(); } public OBB2D getPredictionRect() { return predictionRect; } @Override public void update(float timeStep) { doUpdate(false,timeStep); } public void doUpdate(boolean prediction, float timeStep) { //integrate physics //linear Vector2D acceleration = Vector2D.scalarDivide(forces, mass); if(prediction) { Vector2D velocity = Vector2D.add(this.velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); c = Vector2D.add(getRect().getCenter(), Vector2D.scalarMultiply(velocity , timeStep)); setPredictionCenter(c); //forces = new Vector2D(0,0); //clear forces } else { velocity.x += (acceleration.x * timeStep); velocity.y += (acceleration.y * timeStep); //velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); v.x = getRect().getCenter().getX() + (velocity.x * timeStep); v.y = getRect().getCenter().getY() + (velocity.y * timeStep); deltaVec.x = v.x - c.x; deltaVec.y = v.y - c.y; deltaVec.normalize(); setCenter(v.x, v.y); forces.x = 0; //clear forces forces.y = 0; } //angular float angAcc = torque / inertia; if(prediction) { float angularVelocity = this.angularVelocity + angAcc * timeStep; setPredictionAngle(getAngle() + angularVelocity * timeStep); //torque = 0; //clear torque } else { angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } } public void updatePrediction(float timeStep) { doUpdate(true, timeStep); } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { mat.reset(); Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); relWorldVec.x = Vector2Ds[0]; relWorldVec.y = Vector2Ds[1]; return new Vector2D(Vector2Ds[0], Vector2Ds[1]); } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { mat.reset(); Vector2Ds[0] = world.x; Vector2Ds[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vector2Ds); return new Vector2D(Vector2Ds[0], Vector2Ds[1]); } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { tangent.x = -worldOffset.y; tangent.y = worldOffset.x; return Vector2D.add( Vector2D.scalarMultiply(tangent, angularVelocity) , velocity); } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces.x += worldForce.x; forces.y += worldForce.y; //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } public Vector2D getVelocity() { return velocity; } public void setVelocity(Vector2D velocity) { this.velocity = velocity; } public Vector2D getDeltaVec() { return deltaVec; } } Vehicle public class Wheel { private Vector2D forwardVec; private Vector2D sideVec; private float wheelTorque; private float wheelSpeed; private float wheelInertia; private float wheelRadius; private Vector2D position = new Vector2D(); public Wheel(Vector2D position, float radius) { this.position = position; setSteeringAngle(0); wheelSpeed = 0; wheelRadius = radius; wheelInertia = (radius * radius) * 1.1f; } public void setSteeringAngle(float newAngle) { Matrix mat = new Matrix(); float []vecArray = new float[4]; //forward Vector vecArray[0] = 0; vecArray[1] = 1; //side Vector vecArray[2] = -1; vecArray[3] = 0; mat.postRotate(newAngle / (float)Math.PI * 180.0f); mat.mapVectors(vecArray); forwardVec = new Vector2D(vecArray[0], vecArray[1]); sideVec = new Vector2D(vecArray[2], vecArray[3]); } public void addTransmissionTorque(float newValue) { wheelTorque += newValue; } public float getWheelSpeed() { return wheelSpeed; } public Vector2D getAnchorPoint() { return position; } public Vector2D calculateForce(Vector2D relativeGroundSpeed, float timeStep, boolean prediction) { //calculate speed of tire patch at ground Vector2D patchSpeed = Vector2D.scalarMultiply(Vector2D.scalarMultiply( Vector2D.negative(forwardVec), wheelSpeed), wheelRadius); //get velocity difference between ground and patch Vector2D velDifference = Vector2D.add(relativeGroundSpeed , patchSpeed); //project ground speed onto side axis Float forwardMag = new Float(0.0f); Vector2D sideVel = velDifference.project(sideVec); Vector2D forwardVel = velDifference.project(forwardVec, forwardMag); //calculate super fake friction forces //calculate response force Vector2D responseForce = Vector2D.scalarMultiply(Vector2D.negative(sideVel), 2.0f); responseForce = Vector2D.subtract(responseForce, forwardVel); float topSpeed = 500.0f; //calculate torque on wheel wheelTorque += forwardMag * wheelRadius; //integrate total torque into wheel wheelSpeed += wheelTorque / wheelInertia * timeStep; //top speed limit (kind of a hack) if(wheelSpeed > topSpeed) { wheelSpeed = topSpeed; } //clear our transmission torque accumulator wheelTorque = 0; //return force acting on body return responseForce; } public void setTransmissionTorque(float newValue) { wheelTorque = newValue; } public float getTransmissionTourque() { return wheelTorque; } public void setWheelSpeed(float speed) { wheelSpeed = speed; } } //our vehicle object public class Vehicle extends RigidBody { private Wheel [] wheels = new Wheel[4]; private boolean throttled = false; public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //front wheels wheels[0] = new Wheel(new Vector2D(halfSize.x, halfSize.y), 0.45f); wheels[1] = new Wheel(new Vector2D(-halfSize.x, halfSize.y), 0.45f); //rear wheels wheels[2] = new Wheel(new Vector2D(halfSize.x, -halfSize.y), 0.75f); wheels[3] = new Wheel(new Vector2D(-halfSize.x, -halfSize.y), 0.75f); super.initialize(halfSize, mass, bitmap); } public void setSteering(float steering) { float steeringLock = 0.13f; //apply steering angle to front wheels wheels[0].setSteeringAngle(steering * steeringLock); wheels[1].setSteeringAngle(steering * steeringLock); } public void setThrottle(float throttle, boolean allWheel) { float torque = 85.0f; throttled = true; //apply transmission torque to back wheels if (allWheel) { wheels[0].addTransmissionTorque(throttle * torque); wheels[1].addTransmissionTorque(throttle * torque); } wheels[2].addTransmissionTorque(throttle * torque); wheels[3].addTransmissionTorque(throttle * torque); } public void setBrakes(float brakes) { float brakeTorque = 15.0f; //apply brake torque opposing wheel vel for (Wheel wheel : wheels) { float wheelVel = wheel.getWheelSpeed(); wheel.addTransmissionTorque(-wheelVel * brakeTorque * brakes); } } public void doUpdate(float timeStep, boolean prediction) { for (Wheel wheel : wheels) { float wheelVel = wheel.getWheelSpeed(); //apply negative force to naturally slow down car if(!throttled && !prediction) wheel.addTransmissionTorque(-wheelVel * 0.11f); Vector2D worldWheelOffset = relativeToWorld(wheel.getAnchorPoint()); Vector2D worldGroundVel = pointVelocity(worldWheelOffset); Vector2D relativeGroundSpeed = worldToRelative(worldGroundVel); Vector2D relativeResponseForce = wheel.calculateForce(relativeGroundSpeed, timeStep,prediction); Vector2D worldResponseForce = relativeToWorld(relativeResponseForce); applyForce(worldResponseForce, worldWheelOffset); } //no throttling yet this frame throttled = false; if(prediction) { super.updatePrediction(timeStep); } else { super.update(timeStep); } } @Override public void update(float timeStep) { doUpdate(timeStep,false); } public void updatePrediction(float timeStep) { doUpdate(timeStep,true); } public void inverseThrottle() { float scalar = 0.2f; for(Wheel wheel : wheels) { wheel.setTransmissionTorque(-wheel.getTransmissionTourque() * scalar); wheel.setWheelSpeed(-wheel.getWheelSpeed() * 0.1f); } } } And my big hack collision resolution: private void update() { camera.setPosition((vehicle.getPosition().x * camera.getScale()) - ((getWidth() ) / 2.0f), (vehicle.getPosition().y * camera.getScale()) - ((getHeight() ) / 2.0f)); //camera.move(input.getAnalogStick().getStickValueX() * 15.0f, input.getAnalogStick().getStickValueY() * 15.0f); if(input.isPressed(ControlButton.BUTTON_GAS)) { vehicle.setThrottle(1.0f, false); } if(input.isPressed(ControlButton.BUTTON_STEAL_CAR)) { vehicle.setThrottle(-1.0f, false); } if(input.isPressed(ControlButton.BUTTON_BRAKE)) { vehicle.setBrakes(1.0f); } vehicle.setSteering(input.getAnalogStick().getStickValueX()); //vehicle.update(16.6666666f / 1000.0f); boolean colided = false; vehicle.updatePrediction(16.66666f / 1000.0f); List<Entity> buildings = world.queryStaticSolid(vehicle,vehicle.getPredictionRect()); if(buildings.size() > 0) { colided = true; } if(!colided) { vehicle.update(16.66f / 1000.0f); } else { Vector2D delta = vehicle.getDeltaVec(); vehicle.setVelocity(Vector2D.negative(vehicle.getVelocity().multiply(0.2f)). add(delta.multiply(-1.0f))); vehicle.inverseThrottle(); } } Here is OBB public class OBB2D { // Corners of the box, where 0 is the lower left. private Vector2D corner[] = new Vector2D[4]; private Vector2D center = new Vector2D(); private Vector2D extents = new Vector2D(); private RectF boundingRect = new RectF(); private float angle; //Two edges of the box extended away from corner[0]. private Vector2D axis[] = new Vector2D[2]; private double origin[] = new double[2]; public OBB2D(Vector2D center, float w, float h, float angle) { set(center,w,h,angle); } public OBB2D(float left, float top, float width, float height) { set(new Vector2D(left + (width / 2), top + (height / 2)),width,height,0.0f); } public void set(Vector2D center,float w, float h,float angle) { Vector2D X = new Vector2D( (float)Math.cos(angle), (float)Math.sin(angle)); Vector2D Y = new Vector2D((float)-Math.sin(angle), (float)Math.cos(angle)); X = X.multiply( w / 2); Y = Y.multiply( h / 2); corner[0] = center.subtract(X).subtract(Y); corner[1] = center.add(X).subtract(Y); corner[2] = center.add(X).add(Y); corner[3] = center.subtract(X).add(Y); computeAxes(); extents.x = w / 2; extents.y = h / 2; computeDimensions(center,angle); } private void computeDimensions(Vector2D center,float angle) { this.center.x = center.x; this.center.y = center.y; this.angle = angle; boundingRect.left = Math.min(Math.min(corner[0].x, corner[3].x), Math.min(corner[1].x, corner[2].x)); boundingRect.top = Math.min(Math.min(corner[0].y, corner[1].y),Math.min(corner[2].y, corner[3].y)); boundingRect.right = Math.max(Math.max(corner[1].x, corner[2].x), Math.max(corner[0].x, corner[3].x)); boundingRect.bottom = Math.max(Math.max(corner[2].y, corner[3].y),Math.max(corner[0].y, corner[1].y)); } public void set(RectF rect) { set(new Vector2D(rect.centerX(),rect.centerY()),rect.width(),rect.height(),0.0f); } // Returns true if other overlaps one dimension of this. private boolean overlaps1Way(OBB2D other) { for (int a = 0; a < axis.length; ++a) { double t = other.corner[0].dot(axis[a]); // Find the extent of box 2 on axis a double tMin = t; double tMax = t; for (int c = 1; c < corner.length; ++c) { t = other.corner[c].dot(axis[a]); if (t < tMin) { tMin = t; } else if (t > tMax) { tMax = t; } } // We have to subtract off the origin // See if [tMin, tMax] intersects [0, 1] if ((tMin > 1 + origin[a]) || (tMax < origin[a])) { // There was no intersection along this dimension; // the boxes cannot possibly overlap. return false; } } // There was no dimension along which there is no intersection. // Therefore the boxes overlap. return true; } //Updates the axes after the corners move. Assumes the //corners actually form a rectangle. private void computeAxes() { axis[0] = corner[1].subtract(corner[0]); axis[1] = corner[3].subtract(corner[0]); // Make the length of each axis 1/edge length so we know any // dot product must be less than 1 to fall within the edge. for (int a = 0; a < axis.length; ++a) { axis[a] = axis[a].divide((axis[a].length() * axis[a].length())); origin[a] = corner[0].dot(axis[a]); } } public void moveTo(Vector2D center) { Vector2D centroid = (corner[0].add(corner[1]).add(corner[2]).add(corner[3])).divide(4.0f); Vector2D translation = center.subtract(centroid); for (int c = 0; c < 4; ++c) { corner[c] = corner[c].add(translation); } computeAxes(); computeDimensions(center,angle); } // Returns true if the intersection of the boxes is non-empty. public boolean overlaps(OBB2D other) { if(right() < other.left()) { return false; } if(bottom() < other.top()) { return false; } if(left() > other.right()) { return false; } if(top() > other.bottom()) { return false; } if(other.getAngle() == 0.0f && getAngle() == 0.0f) { return true; } return overlaps1Way(other) && other.overlaps1Way(this); } public Vector2D getCenter() { return center; } public float getWidth() { return extents.x * 2; } public float getHeight() { return extents.y * 2; } public void setAngle(float angle) { set(center,getWidth(),getHeight(),angle); } public float getAngle() { return angle; } public void setSize(float w,float h) { set(center,w,h,angle); } public float left() { return boundingRect.left; } public float right() { return boundingRect.right; } public float bottom() { return boundingRect.bottom; } public float top() { return boundingRect.top; } public RectF getBoundingRect() { return boundingRect; } public boolean overlaps(float left, float top, float right, float bottom) { if(right() < left) { return false; } if(bottom() < top) { return false; } if(left() > right) { return false; } if(top() > bottom) { return false; } return true; } }; What I do is when I predict a hit on the car, I force it back. It does not work that well and seems like a bad idea. What could I do to have more proper collision resolution. Such that if I hit a wall I will never get stuck in it and if I hit the side of a wall I can steer my way out of it. Thanks I found this nice ppt. It talks about pulling objects apart and calculating new velocities. How could I calc new velocities in my case? http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC8QFjAB&url=http%3A%2F%2Fcoitweb.uncc.edu%2F~tbarnes2%2FGameDesignFall05%2FSlides%2FCh4.2-CollDet.ppt&ei=x4ucULy5M6-N0QGRy4D4Cg&usg=AFQjCNG7FVDXWRdLv8_-T5qnFyYld53cTQ&cad=rja

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  • Entity component system -> handling components that depend on one another

    - by jtedit
    I really like the idea of an entity component system and feel it has great flexibility, but have a question. How should dependent components be handled? I'm not talking about how components should communicate with other components they depend on, I have that sorted, but rather how to ensure components are present. For example, an entity cannot have a "velocity" component if it doesn't have a "position" component, in the same way it cant have an "acceleration" component if it doesn't have a "velocity" component. My first idea was every component class overrides an "onAddedToEntity(Entity ent)" function. Then in that function it checks that prerequisite components are also added to the entity, eg: struct EntCompVelocity() : public EntityComponent{ //member variables here void onAddedToEntity(Entity ent){ if(!ent.hasComponent(EntCompPosition::Id)){ ent.addComponent(new EntCompPosition()); } } } This has the nice property that if the acceleration component adds the velocity component, the velocity component will itself add the position component to the entity so dependency "trees" will sort themselves out. However my concern is if I do this components will silently be added with default values and, in the example of adding position, many entities will appear at the origin. Another idea was to simple have the "Entity.addComponent();" function return false if the component's prerequisite components aren't already on the entity, this would force you to manually add the position component and set its value before adding the velocity component. Finally I could simply not ensure a components prerequisite components are added, the "UpdatePosition" system only deals with entities with both a position and velocity component, so therefore adding a velocity component without having a position component wont be a problem (it wont cause crashes due to null pointer/etc), but it does mean entities will carry useless unused data if you add components but not their prerequisite components. Does anyone have experience with this problem and/or any of these methods to solve it? How did you solve the problem?

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  • How to I get a rotated sprite to move left or right?

    - by rphello101
    Using Java/Slick 2D, I'm using the mouse to rotate a sprite on the screen and the directional keys (in this case, WASD) to move the spite. Forwards and backwards is easy, just position += cos(ang)*speed or position -= cos(ang)*speed. But how do I get the sprite to move left or right? I'm thinking it has something to do with adding 90 degrees to the angle or something. Any ideas? Rotation code: int mX = Mouse.getX(); int mY = HEIGHT - Mouse.getY(); int pX = sprite.x+sprite.image.getWidth()/2; int pY = sprite.y+sprite.image.getHeight()/2; double mAng; if(mX!=pX){ mAng = Math.toDegrees(Math.atan2(mY - pY, mX - pX)); if(mAng==0 && mX<=pX) mAng=180; } else{ if(mY>pY) mAng=90; else mAng=270; } sprite.angle = mAng; sprite.image.setRotation((float) mAng); And the movement code (delta is change in time): Input input = gc.getInput(); Vector2f direction = new Vector2f(); Vector2f velocity = new Vector2f(); direction.x = (float) Math.cos(Math.toRadians(sprite.angle)); direction.y = (float) Math.sin(Math.toRadians(sprite.angle)); if(direction.length()>0) direction = direction.normalise(); //On a separate note, what does this line of code do? velocity.x = (float) (direction.x * sprite.moveSpeed); velocity.y = (float) (direction.y * sprite.moveSpeed); if(input.isKeyDown(sprite.up)){ sprite.x += velocity.x*delta; sprite.y += velocity.y*delta; }if (input.isKeyDown(sprite.down)){ sprite.x -= velocity.x*delta; sprite.y -= velocity.y*delta; }if (input.isKeyDown(sprite.left)){ //??? }if (input.isKeyDown(sprite.right)){ //??? }

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  • b2Body moves without stopping

    - by SentineL
    I got a quite strange bug. It is difficult to explain it in two words, but i'll try to do this in short. My b2Body has restitution, friction, density, mass and collision group. I controlling my b2Body via setting linear velocity to it (called on every iteration): (void)moveToDirection:(CGPoint)direction onlyHorizontal:(BOOL)horizontal { b2Vec2 velocity = [controlledObject getBody]-GetLinearVelocity(); double horizontalSpeed = velocity.x + controlledObject.acceleration * direction.x; velocity.x = (float32) (abs((int) horizontalSpeed) < controlledObject.runSpeed ? horizontalSpeed : controlledObject.maxSpeed * direction.x); if (!horizontal) { velocity.y = velocity.y + controlledObject.runSpeed * direction.y; } [controlledObject getBody]->SetLinearVelocity(velocity); } My floor is static b2Body, it has as restitution, friction, density, mass and same collision group in some reason, I'm setting b2Body's friction of my Hero to zero when it is moving, and returning it to 1 when he stops. When I'm pushing run button, hero runs. when i'm releasing it, he stops. All of this works perfect. On jumping, I'm setting linear velocity to my Hero: (void)jump { b2Vec2 velocity = [controlledObject getBody]->GetLinearVelocity(); velocity.y = velocity.y + [[AppDel cfg] getHeroJumpVlelocity]; [controlledObject getBody]->SetLinearVelocity(velocity); } If I'll run, jump, and release run button, while he is in air, all will work fine. And here is my problem: If I'll run, jump, and continue running on landing (or when he goes from one static body to another: there is small fall, probably), Hero will start move, like he has no friction, but he has! I checked this via beakpoints: he has friction, but I can move left of right, and he will never stop, until i'll jump (or go from one static body to another), with unpressed running button. I allready tried: Set friction to body on every iteration double-check am I setting friction to right fixture. set Linear Damping to Hero: his move slows down on gugged moveing. A little more code: I have a sensor and body fixtures in my hero: (void) addBodyFixture { b2CircleShape dynamicBox; dynamicBox.m_radius = [[AppDel cfg] getHeroRadius]; b2FixtureDef bodyFixtureDef; bodyFixtureDef.shape = &dynamicBox; bodyFixtureDef.density = 1.0f; bodyFixtureDef.friction = [[AppDel cfg] getHeroFriction]; bodyFixtureDef.restitution = [[AppDel cfg] getHeroRestitution]; bodyFixtureDef.filter.categoryBits = 0x0001; bodyFixtureDef.filter.maskBits = 0x0001; bodyFixtureDef.filter.groupIndex = 0; bodyFixtureDef.userData = [NSNumber numberWithInt:FIXTURE_BODY]; [physicalBody addFixture:bodyFixtureDef]; } (void) addSensorFixture { b2CircleShape sensorBox; sensorBox.m_radius = [[AppDel cfg] getHeroRadius] * 0.95; sensorBox.m_p.Set(0, -[[AppDel cfg] getHeroRadius] / 10); b2FixtureDef sensor; sensor.shape = &sensorBox; sensor.filter.categoryBits = 0x0001; sensor.filter.maskBits = 0x0001; sensor.filter.groupIndex = 0; sensor.isSensor = YES; sensor.userData = [NSNumber numberWithInt:FIXTURE_SENSOR]; [physicalBody addFixture:sensor]; } Here I'm tracking is hero in air: void FixtureContactListener::BeginContact(b2Contact* contact) { // We need to copy out the data because the b2Contact passed in // is reused. Squirrel *squirrel = (Squirrel *)contact->GetFixtureB()->GetBody()->GetUserData(); if (squirrel) { [squirrel addContact]; } } void FixtureContactListener::EndContact(b2Contact* contact) { Squirrel *squirrel = (Squirrel *)contact->GetFixtureB()->GetBody()->GetUserData(); if (squirrel) { [squirrel removeContact]; } } here is Hero's logic on contacts: - (void) addContact { if (contactCount == 0) [self landing]; contactCount++; } - (void) removeContact { contactCount--; if (contactCount == 0) [self flying]; if (contactCount <0) contactCount = 0; } - (void)landing { inAir = NO; acceleration = [[AppDel cfg] getHeroRunAcceleration]; [sprite stopAllActions]; (running ? [sprite runAction:[self runAction]] : [sprite runAction:[self standAction]]); } - (void)flying { inAir = YES; acceleration = [[AppDel cfg] getHeroAirAcceleration]; [sprite stopAllActions]; [self flyAction]; } here is Hero's moving logic: - (void)stop { running = NO; if (!inAir) { [sprite stopAllActions]; [sprite runAction:[self standAction]]; } } - (void)left { [physicalBody setFriction:0]; if (!running && !inAir) { [sprite stopAllActions]; [sprite runAction:[self runAction]]; } running = YES; moveingDirection = NO; [bodyControls moveToDirection:CGPointMake(-1, 0) onlyHorizontal:YES]; } - (void)right { [physicalBody setFriction:0]; if (!running && !inAir) { [sprite stopAllActions]; [sprite runAction:[self runAction]]; } running = YES; moveingDirection = YES; [bodyControls moveToDirection:CGPointMake(1, 0) onlyHorizontal:YES]; } - (void)jump { if (!inAir) { [bodyControls jump]; } } and here is my update method (called on every iteration): - (void)update:(NSMutableDictionary *)buttons { if (!isDead) { [self updateWithButtonName:BUTTON_LEFT inButtons:buttons whenPressed:@selector(left) whenUnpressed:@selector(stop)]; [self updateWithButtonName:BUTTON_RIGHT inButtons:buttons whenPressed:@selector(right) whenUnpressed:@selector(stop)]; [self updateWithButtonName:BUTTON_UP inButtons:buttons whenPressed:@selector(jump) whenUnpressed:@selector(nothing)]; [self updateWithButtonName:BUTTON_DOWN inButtons:buttons whenPressed:@selector(nothing) whenUnpressed:@selector(nothing)]; [sprite setFlipX:(moveingDirection)]; } [self checkPosition]; if (!running) [physicalBody setFriction:[[AppDel cfg] getHeroFriction]]; else [physicalBody setFriction:0]; } - (void)updateWithButtonName:(NSString *)buttonName inButtons:(NSDictionary *)buttons whenPressed:(SEL)pressedSelector whenUnpressed:(SEL)unpressedSelector { NSNumber *buttonNumber = [buttons objectForKey:buttonName]; if (buttonNumber == nil) return; if ([buttonNumber boolValue]) [self performSelector:pressedSelector]; else [self performSelector:unpressedSelector]; } - (void)checkPosition { b2Body *body = [self getBody]; b2Vec2 position = body->GetPosition(); CGPoint inWorldPosition = [[AppDel cfg] worldMeterPointFromScreenPixel:CGPointMake(position.x * PTM_RATIO, position.y * PTM_RATIO)]; if (inWorldPosition.x < 0 || inWorldPosition.x > WORLD_WIDGH / PTM_RATIO || inWorldPosition.y <= 0) { [self kill]; } }

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  • python Velocity control of the player, why doesn't this work?

    - by Dominic Grenier
    I have the following code inside a while True loop: if abs(playerx) < MAXSPEED: if moveLeft: playerx -= 1 if moveRight: playerx += 1 if abs(playery) < MAXSPEED: if moveDown: playery += 1 if moveUp: playery -= 1 if moveLeft == False and abs(playerx) > 0: playerx += 1 if moveRight == False and abs(playerx) > 0: playerx -= 1 if moveUp == False and abs(playery) > 0: playery += 1 if moveDown == False and abs(playery) > 0: playery -= 1 player.x += playerx player.y += playery if player.left < 0 or player.right > 1000: player.x -= playerx if player.top < 0 or player.bottom > 600: player.y -= playery The intended result is that while an arrow key is pressed, playerx or y increments by one at every loop until it reaches MAXSPEED and stays at MAXSPEED. And that when the player stops pressing that arrow key, his speed decreases. Until it reaches 0. To me, this code explicitly says that... But what actually happens is that playerx or y keeps incrementing regardless of MAXSPEED and continues moving even after the player stops pressing the arrow key. I keep rereading but I'm completely baffled by this weird behavior. Any insights? Thanks.

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  • Velocity control of the player, why doesn't this work?

    - by Dominic Grenier
    I have the following code inside a while True loop: if abs(playerx) < MAXSPEED: if moveLeft: playerx -= 1 if moveRight: playerx += 1 if abs(playery) < MAXSPEED: if moveDown: playery += 1 if moveUp: playery -= 1 if moveLeft == False and abs(playerx) > 0: playerx += 1 if moveRight == False and abs(playerx) > 0: playerx -= 1 if moveUp == False and abs(playery) > 0: playery += 1 if moveDown == False and abs(playery) > 0: playery -= 1 player.x += playerx player.y += playery if player.left < 0 or player.right > 1000: player.x -= playerx if player.top < 0 or player.bottom > 600: player.y -= playery The intended result is that while an arrow key is pressed, playerx or playery increments by one at every iteration until it reaches MAXSPEED and stays at MAXSPEED. And that when the player stops pressing that arrow key, his speed decreases until it reaches 0. To me, this code explicitly says that... But what actually happens is that playerx or playery keeps incrementing regardless of MAXSPEED and continues moving even after the player stops pressing the arrow key. I keep rereading but I'm completely baffled by this weird behavior. Any insights? Thanks.

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  • Bouncing ball isssue

    - by user
    I am currently working on the 2D Bouncing ball physics that bounces the ball up and down. The physics behaviour works fine but at the end the velocity keep +3 then 0 non-stop even the ball has stopped bouncing. How should I modify the code to fix this issue? ballPos = D3DXVECTOR2( 50, 100 ); velocity = 0; accelaration = 3.0f; isBallUp = false; void GameClass::Update() { velocity += accelaration; ballPos.y += velocity; if ( ballPos.y >= 590 ) isBallUp = true; else isBallUp = false; if ( isBallUp ) { ballPos.y = 590; velocity *= -1; } // Graphics Rendering m_Graphics.BeginFrame(); ComposeFrame(); m_Graphics.EndFrame(); }

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  • How to display a projectile trajectory in c++? [on hold]

    - by sana
    I am trying to make a game of Gorillas in c++ whose specification is somewhat like....... is : "In this game both players should select their position on a level scaled ground. Scale of the ground should be from 0 to 20 divisions, each division corresponding to 10 meters. Each player will enter an angle and initial velocity (limits of both should be defined) and the player will hurl a stone with this velocity at given angle. Stone will make a projectile and if it hits the other player then shooting player wins. A random effect of air should also be incorporated. Air will support one player and resist other. Velocity of air should be generated randomly, within some limits, and subtracted or added in the horizontal velocity of the stone. An arrow of suitable length shall represent air direction and velocity. The player who hits first wins." How do I display the trajectory of the stone????

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  • C++ strongly typed typedef

    - by Kian
    I've been trying to think of a way of declaring strongly typed typedefs, to catch a certain class of bugs in the compilation stage. It's often the case that I'll typedef an int into several types of ids, or a vector to position or velocity: typedef int EntityID; typedef int ModelID; typedef Vector3 Position; typedef Vector3 Velocity; This can make the intent of code more clear, but after a long night of coding one might make silly mistakes like comparing different kinds of ids, or adding a position to a velocity perhaps. EntityID eID; ModelID mID; if ( eID == mID ) // <- Compiler sees nothing wrong { /*bug*/ } Position p; Velocity v; Position newP = p + v; // bug, meant p + v*s but compiler sees nothing wrong Unfortunately, suggestions I've found for strongly typed typedefs include using boost, which at least for me isn't a possibility (I do have c++11 at least). So after a bit of thinking, I came upon this idea, and wanted to run it by someone. First, you declare the base type as a template. The template parameter isn't used for anything in the definition, however: template < typename T > class IDType { unsigned int m_id; public: IDType( unsigned int const& i_id ): m_id {i_id} {}; friend bool operator==<T>( IDType<T> const& i_lhs, IDType<T> const& i_rhs ); }; Friend functions actually need to be forward declared before the class definition, which requires a forward declaration of the template class. We then define all the members for the base type, just remembering that it's a template class. Finally, when we want to use it, we typedef it as: class EntityT; typedef IDType<EntityT> EntityID; class ModelT; typedef IDType<ModelT> ModelID; The types are now entirely separate. Functions that take an EntityID will throw a compiler error if you try to feed them a ModelID instead, for example. Aside from having to declare the base types as templates, with the issues that entails, it's also fairly compact. I was hoping anyone had comments or critiques about this idea? One issue that came to mind while writing this, in the case of positions and velocities for example, would be that I can't convert between types as freely as before. Where before multiplying a vector by a scalar would give another vector, so I could do: typedef float Time; typedef Vector3 Position; typedef Vector3 Velocity; Time t = 1.0f; Position p = { 0.0f }; Velocity v = { 1.0f, 0.0f, 0.0f }; Position newP = p + v*t; With my strongly typed typedef I'd have to tell the compiler that multypling a Velocity by a Time results in a Position. class TimeT; typedef Float<TimeT> Time; class PositionT; typedef Vector3<PositionT> Position; class VelocityT; typedef Vector3<VelocityT> Velocity; Time t = 1.0f; Position p = { 0.0f }; Velocity v = { 1.0f, 0.0f, 0.0f }; Position newP = p + v*t; // Compiler error To solve this, I think I'd have to specialize every conversion explicitly, which can be kind of a bother. On the other hand, this limitation can help prevent other kinds of errors (say, multiplying a Velocity by a Distance, perhaps, which wouldn't make sense in this domain). So I'm torn, and wondering if people have any opinions on my original issue, or my approach to solving it.

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  • Why is this class re-initialized every time?

    - by pinnacler
    I have 4 files and the code 'works' as expected. I try to clean everything up, place code into functions, etc... and everything looks fine... and it doesn't work. Can somebody please explain why MatLab is so quirky... or am I just stupid? Normally, I type terminator = simulation(100,20,0,0,0,1); terminator.animate(); and it should produce a map of trees with the terminator walking around in a forest. Everything rotates to his perspective. When I break it into functions... everything ceases to work. I really only changed a few lines of code, shown in comments. Code that works: classdef simulation properties landmarks robot end methods function obj = simulation(mapSize, trees, x,y,heading,velocity) obj.landmarks = landmarks(mapSize, trees); obj.robot = robot(x,y,heading,velocity); end function animate(obj) %Setup Plots fig=figure; xlabel('meters'), ylabel('meters') set(fig, 'name', 'Phil''s AWESOME 80''s Robot Simulator') xymax = obj.landmarks.mapSize*3; xymin = -(obj.landmarks.mapSize*3); l=scatter([0],[0],'bo'); axis([xymin xymax xymin xymax]); obj.landmarks.apparentPositions %Simulation Loop THIS WAS ORGANIZED for n = 1:720, %Calculate and Set Heading/Location obj.robot.headingChange = navigate(n); %Update Position obj.robot.heading = obj.robot.heading + obj.robot.headingChange; obj.landmarks.heading = obj.robot.heading; y = cosd(obj.robot.heading); x = sind(obj.robot.heading); obj.robot.x = obj.robot.x + (x*obj.robot.velocity); obj.robot.y = obj.robot.y + (y*obj.robot.velocity); obj.landmarks.x = obj.robot.x; obj.landmarks.y = obj.robot.y; %Animate set(l,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2)); rectangle('Position',[-2,-2,4,4]); drawnow end end end end ----------- classdef landmarks properties fixedPositions %# positions in a fixed coordinate system. [ x, y ] mapSize = 10; %Map Size. Value is side of square x=0; y=0; heading=0; headingChange=0; end properties (Dependent) apparentPositions end methods function obj = landmarks(mapSize, numberOfTrees) obj.mapSize = mapSize; obj.fixedPositions = obj.mapSize * rand([numberOfTrees, 2]) .* sign(rand([numberOfTrees, 2]) - 0.5); end function apparent = get.apparentPositions(obj) %-STILL ROTATES AROUND ORIGINAL ORIGIN currentPosition = [obj.x ; obj.y]; apparent = bsxfun(@minus,(obj.fixedPositions)',currentPosition)'; apparent = ([cosd(obj.heading) -sind(obj.heading) ; sind(obj.heading) cosd(obj.heading)] * (apparent)')'; end end end ---------- classdef robot properties x y heading velocity headingChange end methods function obj = robot(x,y,heading,velocity) obj.x = x; obj.y = y; obj.heading = heading; obj.velocity = velocity; end end end ---------- function headingChange = navigate(n) %steeringChange = 5 * rand(1) * sign(rand(1) - 0.5); Most chaotic shit %Draw an S if n <270 headingChange=1; elseif n<540 headingChange=-1; elseif n<720 headingChange=1; else headingChange=1; end end Code that does not work... classdef simulation properties landmarks robot end methods function obj = simulation(mapSize, trees, x,y,heading,velocity) obj.landmarks = landmarks(mapSize, trees); obj.robot = robot(x,y,heading,velocity); end function animate(obj) %Setup Plots fig=figure; xlabel('meters'), ylabel('meters') set(fig, 'name', 'Phil''s AWESOME 80''s Robot Simulator') xymax = obj.landmarks.mapSize*3; xymin = -(obj.landmarks.mapSize*3); l=scatter([0],[0],'bo'); axis([xymin xymax xymin xymax]); obj.landmarks.apparentPositions %Simulation Loop for n = 1:720, %Calculate and Set Heading/Location %Update Position headingChange = navigate(n); obj.robot.updatePosition(headingChange); obj.landmarks.updatePerspective(obj.robot.heading, obj.robot.x, obj.robot.y); %Animate set(l,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2)); rectangle('Position',[-2,-2,4,4]); drawnow end end end end ----------------- classdef landmarks properties fixedPositions; %# positions in a fixed coordinate system. [ x, y ] mapSize; %Map Size. Value is side of square x; y; heading; headingChange; end properties (Dependent) apparentPositions end methods function obj = createLandmarks(mapSize, numberOfTrees) obj.mapSize = mapSize; obj.fixedPositions = obj.mapSize * rand([numberOfTrees, 2]) .* sign(rand([numberOfTrees, 2]) - 0.5); end function apparent = get.apparentPositions(obj) %-STILL ROTATES AROUND ORIGINAL ORIGIN currentPosition = [obj.x ; obj.y]; apparent = bsxfun(@minus,(obj.fixedPositions)',currentPosition)'; apparent = ([cosd(obj.heading) -sind(obj.heading) ; sind(obj.heading) cosd(obj.heading)] * (apparent)')'; end function updatePerspective(obj,tempHeading,tempX,tempY) obj.heading = tempHeading; obj.x = tempX; obj.y = tempY; end end end ----------------- classdef robot properties x y heading velocity end methods function obj = robot(x,y,heading,velocity) obj.x = x; obj.y = y; obj.heading = heading; obj.velocity = velocity; end function updatePosition(obj,headingChange) obj.heading = obj.heading + headingChange; tempy = cosd(obj.heading); tempx = sind(obj.heading); obj.x = obj.x + (tempx*obj.velocity); obj.y = obj.y + (tempy*obj.velocity); end end end The navigate function is the same... I would appreciate any help as to why things aren't working. All I did was take the code from the first section from under comment: %Simulation Loop THIS WAS ORGANIZED and break it into 2 functions. One in robot and one in landmarks. Is a new instance created every time because it's constantly printing the same heading for this line int he robot class obj.heading = obj.heading + headingChange;

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  • AABB Sweeping, algorithm to solve "stacking box" problem

    - by Ivo Wetzel
    I'm currently working on a simple AABB collision system and after some fiddling the sweeping of a single box vs. another and the calculation of the response velocity needed to push them apart works flawlessly. Now on to the new problem, imagine I'm having a stack of boxes which are falling towards a ground box which isn't moving: Each of these boxes has a vertical velocity for the "gravity" value, let's say this velocity is 5. Now, the result is that they all fall into each other: The reason is obvious, since all the boxes have a downward velocity of 5, this results in no collisions when calculating the relative velocity between the boxes during sweeping. Note: The red ground box here is static (always 0 velocity, can utilize spatial partitioning ), and all dynamic static collisions are resolved first, thus the fact that the boxes stop correctly at this ground box. So, this seems to be simply an issue with the order the boxes are sweept against each other. I imagine that sorting the boxes based on their x and y velocities and then sweeping these groups correctly against each other may resolve this issues. So, I'm looking for algorithms / examples on how to implement such a system. The code can be found here: https://github.com/BonsaiDen/aabb The two files which are of interest are [box/Dynamic.lua][3] and [box/Manager.lua][4]. The project is using Love2D in case you want to run it.

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  • How can I move along an angled collision at a constant speed?

    - by Raven Dreamer
    I have, for all intents and purposes, a Triangle class that objects in my scene can collide with (In actuality, the right side of a parallelogram). My collision detection and resolution code works fine for the purposes of preventing a gameobject from entering into the space of the Triangle, instead directing the movement along the edge. The trouble is, the maximum speed along the x and y axis is not equivalent in my game, and moving along the Y axis (up or down) should take twice as long as an equivalent distance along the X axis (left or right). Unfortunately, these speeds apply to the collision resolution too, and movement along the blue path above progresses twice as fast. What can I do in my collision resolution to make sure that the speedlimit for Y axis movement is obeyed in the latter case? Collision Resolution for this case below (vecInput and velocity are the position and velocity vectors of the game object): // y = mx+c lowY = 2*vecInput.x + parag.rightYIntercept ; ... else { // y = mx+c // vecInput.y = 2(x) + RightYIntercept // (vecInput.y - RightYIntercept) / 2 = x; //if velocity.Y (positive) greater than velocity.X (negative) //pushing from bottom, so push right. if(velocity.y > -1*velocity.x) { vecInput = new Vector2((vecInput.y - parag.rightYIntercept)/2, vecInput.y); Debug.Log("adjusted rightwards"); } else { vecInput = new Vector2( vecInput.x, lowY); Debug.Log("adjusted downwards"); } }

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  • How to make an object stay relative to another object

    - by Nick
    In the following example there is a guy and a boat. They have both a position, orientation and velocity. The guy is standing on the shore and would like to board. He changes his position so he is now standing on the boat. The boat changes velocity and orientation and heads off. My character however has a velocity of 0,0,0 but I would like him to stay onboard. When I move my character around, I would like to move as if the boat was the ground I was standing on. How do keep my character aligned properly with the boat? It is exactly like in World Of Warcraft, when you board a boat or zeppelin. This is my physics code for the guy and boat: this.velocity.addSelf(acceleration.multiplyScalar(dTime)); this.position.addSelf(this.velocity.clone().multiplyScalar(dTime)); The guy already has a reference to the boat he's standing on, and thus knows the boat's position, velocity, orientation (even matrices or quaternions can be used).

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  • How can I resolve collisions at different speeds, depending on the direction?

    - by Raven Dreamer
    I have, for all intents and purposes, a Triangle class that objects in my scene can collide with (In actuality, the right side of a parallelogram). My collision detection and resolution code works fine for the purposes of preventing a gameobject from entering into the space of the Triangle, instead directing the movement along the edge. The trouble is, the maximum speed along the x and y axis is not equivalent in my game, and moving along the Y axis (up or down) should take twice as long as an equivalent distance along the X axis (left or right). Unfortunately, these speeds apply to the collision resolution too, and movement along the blue path above progresses twice as fast. What can I do in my collision resolution to make sure that the speedlimit for Y axis movement is obeyed in the latter case? Collision Resolution for this case below (vecInput and velocity are the position and velocity vectors of the game object): // y = mx+c // solve for y. M = 2, x = input's x coord, c = rightYIntercept lowY = 2*vecInput.x + parag.rightYIntercept ; ... else { // y = mx+c // vecInput.y = 2(x) + RightYIntercept // (vecInput.y - RightYIntercept) / 2 = x; //if velocity.Y (positive) greater than velocity.X (negative) //pushing from bottom, so push right. if(velocity.y > -1*velocity.x) { //change the input vector's x position to match the //y position on the shape's edge. Formula for line: Y = MX+C // M is 2, C is rightYIntercept, y is the input y, solve for X. vecInput = new Vector2((vecInput.y - parag.rightYIntercept)/2, vecInput.y); Debug.Log("adjusted rightwards"); } else { vecInput = new Vector2( vecInput.x, lowY); Debug.Log("adjusted downwards"); } }

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  • Unity falling body pendulum behaviour

    - by user3447980
    I wonder if someone could provide some guidance. Im attempting to create a pendulum like behaviour in 2D space in Unity without using a hinge joint. Essentially I want to affect a falling body to act as though it were restrained at the radius of a point, and to be subject to gravity and friction etc. Ive tried many modifications of this code, and have come up with some cool 'strange-attractor' like behaviour but i cannot for the life of me create a realistic pendulum like action. This is what I have so far: startingposition = transform.position; //Get start position newposition = startingposition + velocity; //add old velocity newposition.y -= gravity * Time.deltaTime; //add gravity newposition = pivot + Vector2.ClampMagnitude(newposition-pivot,radius); //clamp body at radius??? velocity = newposition-startingposition; //Get new velocity transform.Translate (velocity * Time.deltaTime, Space.World); //apply to transform So im working out the new position based on the old velocity + gravity, then constraining it to a distance from a point, which is the element in the code i cannot get correct. Is this a logical way to go about it?

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  • Moving Character in C# XNA Not working

    - by Matthew Stenquist
    I'm having trouble trying to get my character to move for a game I'm making in my sparetime for the Xbox. However, I can't seem to figure out what I'm doing wrong , and I'm not even sure if I'm doing it right. I've tried googling tutorials on this but I haven't found any helpful ones. Mainly, ones on 3d rotation on the XNA creators club website. My question is : How can I get the character to walk towards the right in the MoveInput() function? What am I doing wrong? Did I code it wrong? The problem is : The player isn't moving. I think the MoveInput() class isn't working. Here's my code from my character class : using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; namespace Jumping { class Character { Texture2D texture; Vector2 position; Vector2 velocity; int velocityXspeed = 2; bool jumping; public Character(Texture2D newTexture, Vector2 newPosition) { texture = newTexture; position = newPosition; jumping = true; } public void Update(GameTime gameTime) { JumpInput(); MoveInput(); } private void MoveInput() { //Move Character right GamePadState gamePad1 = GamePad.GetState(PlayerIndex.One); velocity.X = velocity.X + (velocityXspeed * gamePad1.ThumbSticks.Right.X); } private void JumpInput() { position += velocity; if (GamePad.GetState(PlayerIndex.One).Buttons.A == ButtonState.Pressed && jumping == false) { position.Y -= 1f; velocity.Y = -5f; jumping = true; } if (jumping == true) { float i = 1.6f; velocity.Y += 0.15f * i; } if (position.Y + texture.Height >= 1000) jumping = false; if (jumping == false) velocity.Y = 0f; } public void Draw(SpriteBatch spriteBatch) { spriteBatch.Draw(texture, position, Color.White); } } }

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  • Why does my sprite glitch when moving? [closed]

    - by rphello101
    Using Slick 2D/Java, I'm using the mouse to rotate a sprite and WASD to move it (A and D are used to strafe). I finally got the directional keys and rotation to work in sync, but I'm having problems with sporadic movement. It seems that the move speed is not always set to the value I have it at. Sometimes the sprite with just shoot across the screen. Furthermore, it seems that at 0 degrees, when the left key is pressed, the sprite moves backwards, not to the left. There also seems to be quite a bit of glitching when two keys are pressed, like left and up. Anyone see anything obvious? Here is the rotational code: int mX = Mouse.getX(); int mY = HEIGHT - Mouse.getY(); int pX = sprite.x+sprite.image.getWidth()/2; int pY = sprite.y+sprite.image.getHeight()/2; double mAng; if(mX!=pX){ mAng = Math.toDegrees(Math.atan2(mY - pY, mX - pX)); if(mAng==0 && mX<=pX) mAng=180; } else{ if(mY>pY) mAng=90; else mAng=270; } sprite.angle = mAng; sprite.image.setRotation((float) mAng); Movement code: Input input = gc.getInput(); Vector2f direction = new Vector2f(); Vector2f velocity = new Vector2f(); Vector2f left; Vector2f right; direction.x = (float) Math.cos(Math.toRadians(sprite.angle)); direction.y = (float) Math.sin(Math.toRadians(sprite.angle)); if(direction.length()>0) direction = direction.normalise(); left = new Vector2f(-direction.y, direction.x); right = new Vector2f(direction.y, -direction.x); velocity.x = (float) (direction.x * sprite.moveSpeed); velocity.y = (float) (direction.y * sprite.moveSpeed); if(input.isKeyDown(sprite.up)){ sprite.x += velocity.x*delta; sprite.y += velocity.y*delta; }if (input.isKeyDown(sprite.down)){ sprite.x -= velocity.x*delta; sprite.y -= velocity.y*delta; }if (input.isKeyDown(sprite.left)){ sprite.x += left.x * sprite.moveSpeed * delta; sprite.y += left.y * sprite.moveSpeed * delta; }if (input.isKeyDown(sprite.right)){ sprite.x += right.x * sprite.moveSpeed * delta; sprite.y += right.y * sprite.moveSpeed * delta; }

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