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• Tile-wide extent tracing on a grid.

  - by Larolaro

  I'm currently working on A* pathfinding on a grid and I'm looking to smooth the generated path, while also considering the extent of the character moving along it. I'm using a grid for the pathfinding, however character movement is free roaming, not strict tile to tile movement. To achieve a smoother, more efficient path, I'm doing line traces on a grid to determine if there is unwalkable tiles between tiles to shave off unecessary corners. However, because a line trace is zero extent, it doesn't consider the extent of the character and gives bad results (not returning unwalkable tiles just missed by the line, causing unwanted collisions). So what I'm looking for is rather than a line algorithm that determines the tiles under it, I'm looking for one that determines the tiles under a tile-wide extent line. Here is an image to help visualise my problem! Does anyone have any ideas? I've been working with Bresenham's line and other alternatives but I haven't yet figured out how to nail this specific problem.

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• what's wrong with this Lua code (creating text inside listener in Corona)

  - by Greg

  If you double/triple click on the myObject here the text does NOT disappear. Why is this not working when there are multiple events being fired? That is, are there actually multiple "text" objects, with some existing but no longer having a reference to them held by the local "myText" variable? Do I have to manually removeSelf() on the local "myText" field before assigning it another "display.newText(...)"? display.setStatusBar( display.HiddenStatusBar ) local myText local function hideMyText(event) print ("hideMyText") myText.isVisible = false end local function showTextListener(event) if event.phase == "began" then print("showTextListener") myText = display.newText("Hello World!", 0, 0, native.systemFont, 30) timer.performWithDelay(1000, hideMyText, 1 ) end end -- Display object to press to show text local myObject = display.newImage( "inventory_button.png", display.contentWidth/2, display.contentHeight/2) myObject:addEventListener("touch", showTextListener) Question 2 - Also why is it the case that if I add a line BEFORE "myText = ..." of: a) "if myText then myText:removeSelf() end" = THIS FIXES THINGS, whereas b) "if myText then myText=nil end" = DOES NOT FIX THINGS Interested in hearing how Lua works here re the answer...

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• Moving objects colliding when using unalligned collision avoidance (steering)

  - by James Bedford

  I'm having trouble with unaligned collision avoidance for what I think is a rare case. I have set two objects to move towards each other but with a slight offset, so one of the objects is moving slightly upwards, and one of the objects is moving slightly downwards. In my unaligned collision avoidance steering algorithm I'm finding the points on the object's forward line and the other object's forward line where these two lines are the closest. If these closest points are within a collision avoidance distance, and if the distance between them is smaller than the two radii of the two object's bounding spheres, then the objects should steer away in the appropriate direction. The problem is that for my case, the closest points on the lines are calculated to be really far away from the actual collision point. This is because the two forward lines for each object are moving away from each other as the objects pass. The problem is that because of this, no steering takes place, and the two objects partially collide. Does anyone have any suggestions as to how I can correctly calculate the point of collision? Perhaps by somehow taking into account the size of the two objects?

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• Java keyboard input [on hold]

  - by dØd

  I'm trying to implement a input system that can detect whether a certain key was held or was only pressed briefly. So far I have this: KEY_INTERACTION_TRESHOLD = 400ms //inside a constructor shouldMeasure = true; @Override public void keyPressed(KeyEvent e) { if (shouldMeasure) { startTime = System.currentTimeMillis(); shouldMeasure = false; return; } System.out.println("Button is held down"); e.consume(); } @Override public void keyReleased(KeyEvent e) { if (System.currentTimeMillis() - startTime < KEY_INTERACTION_TRESHOLD) { System.out.println("Button was only pressed briefly"); } startTime = 0; shouldMeasure = true; e.consume(); } Now this works, but the problem is that there is this delay between when I press a key to hold and when the message 'Button is held down' gets displayed. I understand why this delay occurs (for example when you press and hold a letter there will be a similar delay between the first and the second letter printed out), but I would like to somehow avoid it. I'm using only the Java API.

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• libgdx collision detection / bounding the object

  - by johnny-b

  i am trying to get collision detection so i am drawing a red rectangle to see if it is working, and when i do the code below in the update method. to check if it is going to work. the position is not in the right place. the red rectangle starts from the middle and not at the x and y point?Huh so it draws it wrong. i also have a getter method so nothing wrong there. bullet.set(getX(), getY(), getOriginX(), getOriginY()); this is for the render shapeRenderer.begin(ShapeType.Filled); shapeRenderer.setColor(Color.RED); shapeRenderer.rect(bullet.getX(), bullet.getY(), bullet.getOriginX(), bullet.getOriginY(), 15, 5, bullet.getRotation()); shapeRenderer.end(); i have tried to do it with a circle but the circle draws in the middle and i want it to be at the tip of the bullet. at the front of the bullet. x, y point. boundingCircle.set(getX() + getOriginX(), getY() + getOriginY(), 4.0f); shapeRenderer.begin(ShapeType.Filled); shapeRenderer.setColor(Color.RED); shapeRenderer.circle(bullet.getBoundingCircle().x, bullet.getBoundingCircle().y, bullet.getBoundingCircle().radius); shapeRenderer.end(); thank you need it to be of the x and y as the bullet is in the middle of the sprite when drawn originally via paint.

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• How to get a point to the left/right of a vector

  - by MulletDevil

  I have a position vector of a point in space and a quaternion for it's rotation. What i'm trying to calculate is a point too the left and a point to the right. I have the position and rotation(quaternion) of the red dot. What I want is to get the position of the green dots. I have a float value for the distance I want these points to be. With only the position and rotation is it possible to get a unit direction vector pointing left/right which I can multiply by my float value? Edit: I also know the original direction vector.

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• Moving while doing loop animation in RPGMaker

  - by AzDesign

  I made a custom class to display character portrait in RPGMaker XP Here is the class : class Poser attr_accessor :images def initialize @images = Sprite.new @images.bitmap = RPG::Cache.picture('Character.png') #100x300 @images.x = 540 #place it on the bottom right corner of the screen @images.y = 180 end end Create an event on the map to create an instance as global variable, tada! image popped out. Ok nice. But Im not satisfied, Now I want it to have bobbing-head animation-like (just like when we breathe, sometimes bob our head up and down) so I added another method : def move(x,y) @images.x += x @images.y += y end def animate(x,y,step,delay) forward = true 2.times { step.times { wait(delay) if forward move(x/step,y/step) else move(-x/step,-y/step) end } wait(delay*3) forward = false } end def wait(time) while time > 0 time -= 1 Graphics.update end end I called the method to run the animation and it works, so far so good, but the problem is, WHILE the portrait goes up and down, I cannot move my character until the animation is finished. So that's it, I'm stuck in the loop block, what I want is to watch the portrait moving up and down while I walk around village, talk to npc, etc. Anyone can solve my problem ? Or better solution ? Thanks in advance

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• [JOGL] my program is too slow, ho can i profile with Eclipse?

  - by nkint

  hi juys my simple opengl program is really toooo slow and not fluid i'm rendering 30 sphere with simple illumination and simple material. the only hard(?) computing stuffs i do is a collision detection between ray-mouse and spheres (that works ok and i do it only in mouseMoved) i have no thread only animator to move spheres how can i profile my jogl project? or mayebe (most probable..) i have some opengl instruction that i don't understand and make render particular accurate (or back face rendering that i don't need or whatever i don't know exctly i'm just entered in opengl world)

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• Circle-Line Collision Detection Problem

  - by jazzdawg

  I am currently developing a breakout clone and I have hit a roadblock in getting collision detection between a ball (circle) and a brick (convex polygon) working correctly. I am using a Circle-Line collision detection test where each line represents and edge on the convex polygon brick. For the majority of the time the Circle-Line test works properly and the points of collision are resolved correctly. Collision detection working correctly. However, occasionally my collision detection code returns false due to a negative discriminant when the ball is actually intersecting the brick. Collision detection failing. I am aware of the inefficiency with this method and I am using axis aligned bounding boxes to cut down on the number of bricks tested. My main concern is if there are any mathematical bugs in my code below. /* * from and to are points at the start and end of the convex polygons edge. * This function is called for every edge in the convex polygon until a * collision is detected. */ bool circleLineCollision(Vec2f from, Vec2f to) { Vec2f lFrom, lTo, lLine; Vec2f line, normal; Vec2f intersectPt1, intersectPt2; float a, b, c, disc, sqrt_disc, u, v, nn, vn; bool one = false, two = false; // set line vectors lFrom = from - ball.circle.centre; // localised lTo = to - ball.circle.centre; // localised lLine = lFrom - lTo; // localised line = from - to; // calculate a, b & c values a = lLine.dot(lLine); b = 2 * (lLine.dot(lFrom)); c = (lFrom.dot(lFrom)) - (ball.circle.radius * ball.circle.radius); // discriminant disc = (b * b) - (4 * a * c); if (disc < 0.0f) { // no intersections return false; } else if (disc == 0.0f) { // one intersection u = -b / (2 * a); intersectPt1 = from + (lLine.scale(u)); one = pointOnLine(intersectPt1, from, to); if (!one) return false; return true; } else { // two intersections sqrt_disc = sqrt(disc); u = (-b + sqrt_disc) / (2 * a); v = (-b - sqrt_disc) / (2 * a); intersectPt1 = from + (lLine.scale(u)); intersectPt2 = from + (lLine.scale(v)); one = pointOnLine(intersectPt1, from, to); two = pointOnLine(intersectPt2, from, to); if (!one && !two) return false; return true; } } bool pointOnLine(Vec2f p, Vec2f from, Vec2f to) { if (p.x >= min(from.x, to.x) && p.x <= max(from.x, to.x) && p.y >= min(from.y, to.y) && p.y <= max(from.y, to.y)) return true; return false; }

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• Examples of good Javascript/HTML5 based games

  - by Zuch

  Now that Flash is largely being replaced with HTML5 elements (video, audio, canvas, etc.) are there any good examples of web-based games built on completely open standards (meaning Javascript, HTML and CSS)? I see a lot of examples of pure HTML5 implementations of what was once only in Flash (like stuff here: http://www.html5rocks.com/) but not many games, a domain which still seem dominated by Flash. I'm curious what's possible and what the limitations are.

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• One Step-Ahead A-Star

  - by Jonathan Dickinson

  I am attempting to create a server-centric RTS (as opposed to usual parallel synchronised simulation route of most RTS games today) - however I am still leveraging the discreet N-turns-ahead paradigm discussed by one of the AOE developers on Gamasutra. I have [possibly questionably?] decided that the path finding should only ever find the next cell the entity needs to move to, and was wondering if anyone has any clever ideas on how to optimize the algorithm for this specific scenario - or any other ideas on how to keep the pathfinding as lean as possible on the server. I have investigated a few possible algorithms but could only come up with one appropriation: Tiered A-Star - Relatively large T1 tiles, work out (and cache) each cell as you enter it. Other than that: doing the full A-Star pass and caching the entire path, which might use too much memory if a large amount of units are present. I know about the existence of naive progressive pathfinding algorithms (if you hit a block, turn in the direction closer to your target etc.) but they suffer from infinite feedback loops - and very poor pathing even if visited blocks are memorised. Not an option. Many thanks.

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• GLSL: Strange light reflections

  - by Tom

  According to this tutorial I'm trying to make a normal mapping using GLSL, but something is wrong and I can't find the solution. The output render is in this image: Image1 in this image is a plane with two triangles and each of it is different illuminated (that is bad). The plane has 6 vertices. In the upper left side of this plane are 2 identical vertices (same in the lower right). Here are some vectors same for each vertice: normal vector = 0, 1, 0 (red lines on image) tangent vector = 0, 0,-1 (green lines on image) bitangent vector = -1, 0, 0 (blue lines on image) here I have one question: The two identical vertices does need to have the same tangent and bitangent? I have tried to make other values to the tangents but the effect was still similar. Here are my shaders Vertex shader: #version 130 // Input vertex data, different for all executions of this shader. in vec3 vertexPosition_modelspace; in vec2 vertexUV; in vec3 vertexNormal_modelspace; in vec3 vertexTangent_modelspace; in vec3 vertexBitangent_modelspace; // Output data ; will be interpolated for each fragment. out vec2 UV; out vec3 Position_worldspace; out vec3 EyeDirection_cameraspace; out vec3 LightDirection_cameraspace; out vec3 LightDirection_tangentspace; out vec3 EyeDirection_tangentspace; // Values that stay constant for the whole mesh. uniform mat4 MVP; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Output position of the vertex, in clip space : MVP * position gl_Position = MVP * vec4(vertexPosition_modelspace,1); // Position of the vertex, in worldspace : M * position Position_worldspace = (M * vec4(vertexPosition_modelspace,1)).xyz; // Vector that goes from the vertex to the camera, in camera space. // In camera space, the camera is at the origin (0,0,0). vec3 vertexPosition_cameraspace = ( V * M * vec4(vertexPosition_modelspace,1)).xyz; EyeDirection_cameraspace = vec3(0,0,0) - vertexPosition_cameraspace; // Vector that goes from the vertex to the light, in camera space. M is ommited because it's identity. vec3 LightPosition_cameraspace = ( V * vec4(LightPosition_worldspace,1)).xyz; LightDirection_cameraspace = LightPosition_cameraspace + EyeDirection_cameraspace; // UV of the vertex. No special space for this one. UV = vertexUV; // model to camera = ModelView vec3 vertexTangent_cameraspace = MV3x3 * vertexTangent_modelspace; vec3 vertexBitangent_cameraspace = MV3x3 * vertexBitangent_modelspace; vec3 vertexNormal_cameraspace = MV3x3 * vertexNormal_modelspace; mat3 TBN = transpose(mat3( vertexTangent_cameraspace, vertexBitangent_cameraspace, vertexNormal_cameraspace )); // You can use dot products instead of building this matrix and transposing it. See References for details. LightDirection_tangentspace = TBN * LightDirection_cameraspace; EyeDirection_tangentspace = TBN * EyeDirection_cameraspace; } Fragment shader: #version 130 // Interpolated values from the vertex shaders in vec2 UV; in vec3 Position_worldspace; in vec3 EyeDirection_cameraspace; in vec3 LightDirection_cameraspace; in vec3 LightDirection_tangentspace; in vec3 EyeDirection_tangentspace; // Ouput data out vec3 color; // Values that stay constant for the whole mesh. uniform sampler2D DiffuseTextureSampler; uniform sampler2D NormalTextureSampler; uniform sampler2D SpecularTextureSampler; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Light emission properties // You probably want to put them as uniforms vec3 LightColor = vec3(1,1,1); float LightPower = 40.0; // Material properties vec3 MaterialDiffuseColor = texture2D( DiffuseTextureSampler, vec2(UV.x,-UV.y) ).rgb; vec3 MaterialAmbientColor = vec3(0.1,0.1,0.1) * MaterialDiffuseColor; //vec3 MaterialSpecularColor = texture2D( SpecularTextureSampler, UV ).rgb * 0.3; vec3 MaterialSpecularColor = vec3(0.5,0.5,0.5); // Local normal, in tangent space. V tex coordinate is inverted because normal map is in TGA (not in DDS) for better quality vec3 TextureNormal_tangentspace = normalize(texture2D( NormalTextureSampler, vec2(UV.x,-UV.y) ).rgb*2.0 - 1.0); // Distance to the light float distance = length( LightPosition_worldspace - Position_worldspace ); // Normal of the computed fragment, in camera space vec3 n = TextureNormal_tangentspace; // Direction of the light (from the fragment to the light) vec3 l = normalize(LightDirection_tangentspace); // Cosine of the angle between the normal and the light direction, // clamped above 0 // - light is at the vertical of the triangle -> 1 // - light is perpendicular to the triangle -> 0 // - light is behind the triangle -> 0 float cosTheta = clamp( dot( n,l ), 0,1 ); // Eye vector (towards the camera) vec3 E = normalize(EyeDirection_tangentspace); // Direction in which the triangle reflects the light vec3 R = reflect(-l,n); // Cosine of the angle between the Eye vector and the Reflect vector, // clamped to 0 // - Looking into the reflection -> 1 // - Looking elsewhere -> < 1 float cosAlpha = clamp( dot( E,R ), 0,1 ); color = // Ambient : simulates indirect lighting MaterialAmbientColor + // Diffuse : "color" of the object MaterialDiffuseColor * LightColor * LightPower * cosTheta / (distance*distance) + // Specular : reflective highlight, like a mirror MaterialSpecularColor * LightColor * LightPower * pow(cosAlpha,5) / (distance*distance); //color.xyz = E; //color.xyz = LightDirection_tangentspace; //color.xyz = EyeDirection_tangentspace; } I have replaced the original color value by EyeDirection_tangentspace vector and then I got other strange effect but I can not link the image (not eunogh reputation) Is it possible that with this shaders is something wrong, or maybe in other place in my code e.g with my matrices? SOLVED Solved... 3 days needed for changing one letter from this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(12*sizeof(float)) // array buffer offset ); to this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(11*sizeof(float)) // array buffer offset ); see difference? :)

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• Java: Reflection Packet Builder using getField()

  - by Matchlighter

  So I just finished writing a packet builder that dynamically loads data into a data stream which is then sent out. Each builder operates by finding fields in its class (and its superclasses) that are marked with an @data annotation. Upon finishing the builder, I remembered that getFields() does not return in "any specific order". I quite like my builder because it allows for quite simple, yet hard-typed packets. Could this implementation be a problem? What would be the best next step to keep the simplicity - do alphabetical sorting of fields?

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• How i can sign and/or group a specific set of vertices in a 3D file container like OBJ ? - in Blender

  - by user827992

  I would like to export a 3D model with each part having a name or a label if you will. For example i would like to export a model of an human body and name each part in specifics vertex groups like: left hand, right hand, right foot, head, ears, ... and you got the idea; so i can have a single 3D model that i can explode in various parts if needed. If there is a better technique about how to mark vertex groups in a 3D file please share your solution. As 3D editor i use Blender.

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• Calculating up-vector to avoid gimbal lock using euler angles

  - by jessejuicer

  I wish to orbit a camera around a sphere, yet the problem is that when the camera rotates so that it is at the north pole (and pointing down) or the south pole (and pointing up) of the sphere the camera doesn't handle itself very well. It spins rapidly until arriving 180 degrees in the opposite direction. I believe this is known as gimbal lock. I understand you can avoid this problem using quaternions. But I also read in another forum that it's possible to avoid this easily using euler angles as well. Which I would prefer to do. It was said that all you need to do is "calculate a proper up-vector every frame, and that avoids the problem entirely." Well, I tried aligning the up-vector with the vertical axis of the camera whenever the camera changed orientation, but this didn't seem to work. Meaning that the up-vector followed exactly the orientation of the camera's y-axis (or it's up vector), instead of using a constant up-vector aligned to the up-vector of the world (0, 1, 0). How exactly do I go about calculating a proper up-vector as my camera orientation changes to avoid the gimbal lock problem mentioned above?

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• Vector vs Scalar velocity?

  - by Serguei Fedorov

  I am revamping an engine I have been working on and off on for the last few weeks to use a directional vector to dictate direction; this way I can dictate the displacement based on a direction. However, the issue I am trying to overcome is the following problem; the speed towards X and speed towards Y are unrelated to one another. If gravity pulls the object down by an increasing velocity my velocity towards the X should not change. This is very easy to implement if my speed is broken into a Vector datatype, Vector.X dictates one direction Vector.Y dictates the other (assuming we are not concerned about the Z axis). However, this defeats the purpose of the directional vector because: SpeedX = 10 SpeedY = 15 [1, 1] normalized = ~[0.7, 0.7] [0.7, 0.7] * [10, 15] = [7, 10.5] As you can see my direction is now "scaled" to my speed which is no longer the direction that I want to be moving in. I am very new to vector math and this is a learning project for me. I looked around a little bit on the internet but I still want to figure out things on my own (not just look at an example and copy off it). Is there way around this? Using a directional vector is extremely useful but I am a little bit stumped at this problem. I am sorry if my mathematical understanding maybe completely wrong.

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• Scaling along an arbitrary axis (Dealing with non-uniform scale)

  - by Jon

  I'm trying to build my own little engine to get more familiar with the concepts of 3D programming. I have a transform class that on each frame it creates a Scaling Matrix (S), a Rotation Matrix from a Quaternion (R) and concatenates them together (S*R). Once i have SR, I insert the translation values into the bottom of the three columns. So i end up with a transformation matrix that looks like: [SR SR SR 0] [SR SR SR 0] [SR SR SR 0] [tx ty tz 1] This works perfectly in all cases except when rotating an object that has a non-uniform scale. For example a unit cube with ScaleX = 4, ScaleY = 2, ScaleZ = 1 will give me a rectangular box that is 4 times as wide as the depth and twice as high as the depth. If i then translate this around, the box stays the same and looks normal. The problem happens whenever I try to rotate this scaled box. The shape itself becomes distorted and it appears as though the Scale factors are affecting the object on the World X,Y,Z axis rather than the local X,Y,Z axis of the object. I've done some pretty extensive research through a variety of textbooks (Eberly, Moller/Hoffman, Phar etc) and there isn't a ton there to go off of. Online, most of the answers say to avoid non-uniform scaling which I understand the desire to avoid it, but I'd still like to figure out how to support it. The only thing I can think off is that when constructing a Scale Matrix: [sx 0 0 0] [0 sy 0 0] [0 0 sz 0] [0 0 0 1] This is scaling along the World Axis instead of the object's local Direction, Up and Right vectors or it's local Z, Y, X axis. Does anyone have any tips or ideas on how to handle construction a transformation matrix that allows for non-uniform scaling and rotation? Thanks!

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• 3d trajectory - calculate initial velocity

  - by Skoder

  Hey, I've got a 2D projectile code sample working, but would like to extend it to 3D. How would I calculate the initial velocity of the Z-axis? At the moment, I've got: initVel.X = (float)Math.Cos(45.0); initVel.Y = (float)Math.Sin(45.0); How would I convert this to work in 3D (and add the initial velocity for the Z-axis)? In my example, X is across, Y is up down and Z is going into the screen. I also normalize the vector and multiply it by the speed. Thanks

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• Rotating a cube using jBullet collisions

  - by Kenneth Bray

  How would one go about rotating/flipping a cube with the physics of jBullet? Here is my Draw method for my cube object: public void Draw() { // center point posX, posY, posZ float radius = .25f;//size / 2; glPushMatrix(); glBegin(GL_QUADS); //top { glColor3f(5.0f,1.0f,5.0f); // white glVertex3f(posX + radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY + radius, posZ + radius); } //bottom { glColor3f(1.0f,1.0f,0.0f); // ?? color glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY - radius, posZ - radius); } //right side { glColor3f(1.0f,0.0f,1.0f); // ?? color glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } //left side { glColor3f(0.0f,1.0f,1.0f); // ?? color glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); } //front side { glColor3f(0.0f,0.0f,1.0f); // blue glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); } //back side { glColor3f(0.0f,1.0f,0.0f); // green glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } glEnd(); glPopMatrix(); Update(); } This is my update method for the cube position: public void Update() { Transform trans = new Transform(); cubeRigidBody.getMotionState().getWorldTransform(trans); posX = trans.origin.x; posY = trans.origin.y; posZ = trans.origin.z; Quat4f outRot = new Quat4f(); trans.getRotation(outRot); rotX = outRot.x; rotY = outRot.y; rotZ = outRot.z; rotW = outRot.w; } I am assuming I need to use glrotatef, but it does not seem to work at all when I try that.. this is how I have tried to rotate the cubes: GL11.glRotatef(rotW, rotX, 0.0f, 0.0f); GL11.glRotatef(rotW, 0.0f, rotY, 0.0f); GL11.glRotatef(rotW, 0.0f, 0.0f, rotZ);

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• Per-pixel collision detection - why does XNA transform matrix return NaN when adding scaling?

  - by JasperS

  I looked at the TransformCollision sample on MSDN and added the Matrix.CreateTranslation part to a property in my collision detection code but I wanted to add scaling. The code works fine when I leave scaling commented out but when I add it and then do a Matrix.Invert() on the created translation matrix the result is NaN ({NaN,NaN,NaN},{NaN,NaN,NaN},...) Can anyone tell me why this is happening please? Here's the code from the sample: // Build the block's transform Matrix blockTransform = Matrix.CreateTranslation(new Vector3(-blockOrigin, 0.0f)) * // Matrix.CreateScale(block.Scale) * would go here Matrix.CreateRotationZ(blocks[i].Rotation) * Matrix.CreateTranslation(new Vector3(blocks[i].Position, 0.0f)); public static bool IntersectPixels( Matrix transformA, int widthA, int heightA, Color[] dataA, Matrix transformB, int widthB, int heightB, Color[] dataB) { // Calculate a matrix which transforms from A's local space into // world space and then into B's local space Matrix transformAToB = transformA * Matrix.Invert(transformB); // When a point moves in A's local space, it moves in B's local space with a // fixed direction and distance proportional to the movement in A. // This algorithm steps through A one pixel at a time along A's X and Y axes // Calculate the analogous steps in B: Vector2 stepX = Vector2.TransformNormal(Vector2.UnitX, transformAToB); Vector2 stepY = Vector2.TransformNormal(Vector2.UnitY, transformAToB); // Calculate the top left corner of A in B's local space // This variable will be reused to keep track of the start of each row Vector2 yPosInB = Vector2.Transform(Vector2.Zero, transformAToB); // For each row of pixels in A for (int yA = 0; yA < heightA; yA++) { // Start at the beginning of the row Vector2 posInB = yPosInB; // For each pixel in this row for (int xA = 0; xA < widthA; xA++) { // Round to the nearest pixel int xB = (int)Math.Round(posInB.X); int yB = (int)Math.Round(posInB.Y); // If the pixel lies within the bounds of B if (0 <= xB && xB < widthB && 0 <= yB && yB < heightB) { // Get the colors of the overlapping pixels Color colorA = dataA[xA + yA * widthA]; Color colorB = dataB[xB + yB * widthB]; // If both pixels are not completely transparent, if (colorA.A != 0 && colorB.A != 0) { // then an intersection has been found return true; } } // Move to the next pixel in the row posInB += stepX; } // Move to the next row yPosInB += stepY; } // No intersection found return false; }

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• Optimized algorithm for line-sphere intersection in GLSL

  - by fernacolo

  Well, hello then! I need to find intersection between line and sphere in GLSL. Right now my solution is based on Paul Bourke's page and was ported to GLSL this way: // The line passes through p1 and p2: vec3 p1 = (...); vec3 p2 = (...); // Sphere center is p3, radius is r: vec3 p3 = (...); float r = ...; float x1 = p1.x; float y1 = p1.y; float z1 = p1.z; float x2 = p2.x; float y2 = p2.y; float z2 = p2.z; float x3 = p3.x; float y3 = p3.y; float z3 = p3.z; float dx = x2 - x1; float dy = y2 - y1; float dz = z2 - z1; float a = dx*dx + dy*dy + dz*dz; float b = 2.0 * (dx * (x1 - x3) + dy * (y1 - y3) + dz * (z1 - z3)); float c = x3*x3 + y3*y3 + z3*z3 + x1*x1 + y1*y1 + z1*z1 - 2.0 * (x3*x1 + y3*y1 + z3*z1) - r*r; float test = b*b - 4.0*a*c; if (test >= 0.0) { // Hit (according to Treebeard, "a fine hit"). float u = (-b - sqrt(test)) / (2.0 * a); vec3 hitp = p1 + u * (p2 - p1); // Now use hitp. } It works perfectly! But it seems slow... I'm new at GLSL. You can answer this questions in two ways: Tell me there is no solution, showing some proof or strong evidence. Tell me about GLSL features (vector APIs, primitive operations) that makes the above algorithm faster, showing some example. Thanks a lot!

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• Circle collision detection and Vector math: HELP?

  - by Griffin

  Hey so i'm currently going through the wildbunny blog to learn about collision detection, but i'm a bit confused on how the vectors he's talking about come into play QUOTED BLOG: p = ||A-B|| – (r1+r2) The two spheres are penetrating by distance p. We would also like the penetration vector so that we can correct the penetration once we discover it. This is the vector that moves both circles to the point where they just touch, correcting the penetration. Importantly it is not only just a vector that does this, it is the only vector which corrects the penetration by moving the minimum amount. This is important because we only want to correct the error, not introduce more by moving too much when we correct, or too little. N = (A-B) / ||A-B|| P = N*p Here we have calculated the normalised vector N between the two centres and the penetration vector P by multiplying our unit direction by the penetration distance. Ok so i understand that p is the distance each circle is penetrating each other, but i don't get what exactly N and P is. it seems to me N is just the coordinates of the 3rd point of the right trianlge formed by point A and B (A-B) then being divided by the hypotenuse of that triangle or distance between A and B (||A-B||) Whats the significance of this? Also, what is the penetration vector used for? It seems to me like a movement that one of the circles would perform to get un-penetrated.

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• XNA hlsl tex2D() only reads 3 channels from normal maps and specular maps

  - by cubrman

  Our engine uses deferred rendering and at the main draw phase gathers plenty of data from the objects it draws. In order to save on tex2D calls, we packed our objects' specular maps with all sorts of data, so three out of four channels are already taken. To make it clear: I am talking about the assets that come with the models and are stored in their material's Specular Level channel, not about the RenderTarget. So now I need another information to be stored in the alpha channel, but I cannot make the shader to read it properly! Nomatter what I write into alpha it ends up being 1 (255)! I tried: saving the textures in PNG/TGA formats. turning off pre-computed alpha in model's properties. Out of every texture available to me (we use Diffuse map, Normal Map and Specular Map) I was only able to read alpha successfully from the Diffuse Map! Here is how I add specular and normal maps to my model's material in the content processor: if (geometry.Material.Textures.ContainsKey(normalMapKey)) { ExternalReference<TextureContent> texRef = geometry.Material.Textures[normalMapKey]; geometry.Material.Textures.Remove("NormalMap"); geometry.Material.Textures.Add("NormalMap", texRef); } ... foreach (KeyValuePair<String, ExternalReference<TextureContent>> texture in material.Textures) { if ((texture.Key == "Texture") || (texture.Key == "NormalMap") || (texture.Key == "SpecularMap")) mat.Textures.Add(texture.Key, texture.Value); } In the shader I obviously use: float4 data = tex2D(specularMapSampler, TexCoords); so data.a is always 1 in my case, could you suggest a reason?

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• How to create custom bitmap .fnt font? [duplicate]

  - by Kolesnikovich Dmitry

  This question already has an answer here: Tool to create a bitmap font from a true type font 12 answers Bitmap font generator http://www.angelcode.com/products/bmfont can creates fonts in black and white only. I'm looking for more advanced tool. Share you experience on it please. Thanks in advance. (Output file format is .fnt)

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• Suggestions to start a cross-platform project

  - by Gabriele

  I have a big project in my head, it should be cross-platform (Win, Max and Linux), online (Client - Server) and with 3D graphics. I would like some suggestions to start with the right things. Currently I'm a PHP/MySQL coder, I used to code in C and Pascal on DOS ages (Borland Times ;)), my C knowlegde need a refresh but it's ok. I guess C++ it's the right language. What platform and what i should use to code? I can choose from all three platforms. My idea was to use Visual Studio 2010 C++, but i'm not sure if it support Native code. What kind of libraries should i use? I guessed OpenSSL for the login, OpenGL for graphics part. For the Audio or the GUI? Any other suggestions are well accepted. I know it's a "BIG DEAL" but I have no rush and it'll be a free-time project, only for my pleasure. Thank you in advance.

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