embedded development - Page 426

How to position a sprite in a 2D animation skeleton?

- by Paul Manta

Given two joints that define a bone, I would like to know how to decide where, between those two joints, I should draw the sprite. This should be a fairly simple thing to solve, but there is one thing that I am not sure about. After I've determined the rotation of the sprite (which is the absolute angle the joints form with the x-axis), I also need to determine the origin point from where I need to start drawing the transformed image. So how should I position the sprite between the two joints? Should I make the center of the image be the midpoint between the two joints, or should I make one the of the joints be the origin? Do these things matter that much (could the wrong positioning make the sprite move oddly during the animation)?

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Organising levels / rooms in a MUD-style text based world

- by Polynomial

I'm thinking of writing a small text-based adventure game, but I'm not particularly sure how I should design the world from a technical standpoint. My first thought is to do it in XML, designed something like the following. Apologies for the huge pile of XML, but I felt it important to fully explain what I'm doing. <level> <start>  <room>Kitchen</room> <inventory></inventory> </start> <rooms> <room> <name>Kitchen</name> <description>A small kitchen that looks like it hasn't been used in a while. It has a table in the middle, and there are some cupboards. There is a door to the north, which leads to the garden.</description>  <objects> <object>Cupboards</object> <object>Knife</object> <object>Batteries</object> </objects> </room> <room> <name>Garden</name> <description>The garden is wild and full of prickly bushes. To the north there is a path, which leads into the trees. To the south there is a house.</description> <objects> </objects> </room> <room> <name>Woods</name> <description>The woods are quite dark, with little light bleeding in from the garden. It is eerily quiet.</description> <objects> <object>Trees01</object> </objects> </room> </rooms> <doors>  <door> <type>door</type> <direction>N</direction> <from>Kitchen</from> <to>Garden</to> </door> <door> <type>path</type> <direction>N</direction> <from>Garden</type> <to>Woods</type> </door> </doors> <variables>  <variable name="cupboard_open">0</variable> </variables> <objects>  <object> <name>Trees01</name> <displayName>Trees</displayName> <actions>  <action> <command>EXAMINE</command> <message>The trees are tall and thick. There aren't any low branches, so it'd be difficult to climb them.</message> </action> </actions> </object> <object> <name>Cupboards</name> <displayName>Cupboards</displayName> <actions> <action>  <requirements>  <require operation="equal" value="1">cupboard_open</require> </requirements> <command>EXAMINE</command>  <failMessage>The cupboard is closed.</failMessage> <message>The cupboard contains some batteires.</message> </action> <action> <requirements> <require operation="equal" value="0">cupboard_open</require> </requirements> <command>OPEN</command> <failMessage>The cupboard is already open.</failMessage> <message>You open the cupboard. It contains some batteries.</message>  <assigns> <assign operation="set" value="1">cupboard_open</assign> </assigns> </action> <action> <requirements> <require operation="equal" value="1">cupboard_open</require> </requirements> <command>CLOSE</command> <failMessage>The cupboard is already closed.</failMessage> <message>You closed the cupboard./message> <assigns> <assign operation="set" value="0">cupboard_open</assign> </assigns> </action> </actions> </object> <object> <name>Batteries</name> <displayName>Batteries</displayName>  <inventory>1</inventory> <actions> <action> <requirements> <require operation="equal" value="1">cupboard_open</require> </requirements> <command>GET</command>  <message>You picked up the batteries.</message> </action> </actions> </object> </objects> </level> Obviously there'd need to be more to it than this. Interaction with people and enemies as well as death and completion are necessary additions. Since the XML is quite difficult to work with, I'd probably create some sort of world editor. I'd like to know if this method has any downfalls, and if there's a "better" or more standard way of doing it.

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Unity: Assigning a key to perform an action in the inspector

- by Marc Pilgaard

I am trying to write a simple piece of code in JavaScript where a button toggles the activation of a shield, by dragging a prefab with Resources.load("ActivateShieldPreFab") and destroying it again (Haven't implemented that yet). I wish to assign this button through the inspector, so I have created a string variable which appears as intended in the inspector. Though it doesn't seem to register the inspector input, even though I changed the value through the inspector. It only provides the error: "Input Key named: is unknown" When the button name is assigned within the code, there is no issues. Code as follows: var ShieldOn = false; var stringbutton : String; function Start(){ } function Update () { if(Input.GetKey(stringbutton) && ShieldOn != true) { Instantiate(Resources.load("ActivateShieldPreFab"), Vector3 (0, 0, 0), Quaternion.identity); ShieldOn = true; } }

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How to read BC4 texture in GLSL?

- by Question

I'm supposed to receive a texture in BC4 format. In OpenGL, i guess this format is called GL_COMPRESSED_RED_RGTC1. The texture is not really a "texture", more like a data to handle at fragment shader. Usually, to get colors from a texture within a fragment shader, i do : uniform sampler2D TextureUnit; void main() { vec4 TexColor = texture2D(TextureUnit, vec2(gl_TexCoord[0])); (...) the result of which is obviously a v4, for RGBA. But now, i'm supposed to receive a single float from the read. I'm struggling to understand how this is achieved. Should i still use a texture sampler, and expect the value to be in a specific position (for example, within TexColor.r ?), or should i use something else ?

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General visual effects to meshes/entities

- by Pacha

I am trying to add some visual effects to some entities, meshes, or whatever you want to call them as they are looking pretty dull in my game right now. What I want to achieve is this: http://youtu.be/zox8935PLw0?t=36s (the "texture" gets disintegrated and then goes back to normal, covering the whole mesh.) Also I would like to know what is the best way to add effects like the one in the video to my game (for example, thunder effects, shattering, etc.) I know that I can do some things with shaders, but I haven't learned them too well and I am still in a beginner level. I am using Ogre3D, and GLSL for shaders. Thanks! Note: this is a screen-shot of my game, I want to apply the effect in the video to my main character):

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How Do I Search For Struct Items In A Vector? [migrated]

- by Vladimir Marenus

I'm attempting to create an inventory system using a vector implementation, but I seem to be having some troubles. I'm running into issues using a struct I made. NOTE: This isn't actually in a game code, this is a separate Solution I am using to test my knowledge of vectors and structs! struct aItem { string itemName; int damage; }; int main() { aItem healingPotion; healingPotion.itemName = "Healing Potion"; healingPotion.damage= 6; aItem fireballPotion; fireballPotion.itemName = "Potion of Fiery Balls"; fireballPotion.damage = -2; vector<aItem> inventory; inventory.push_back(healingPotion); inventory.push_back(healingPotion); inventory.push_back(healingPotion); inventory.push_back(fireballPotion); if(find(inventory.begin(), inventory.end(), fireballPotion) != inventory.end()) { cout << "Found"; } system("PAUSE"); return 0; } The preceeding code gives me the following error: 1c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(3186): error C2678: binary '==' : no operator found which takes a left-hand operand of type 'aItem' (or there is no acceptable conversion) There is more to the error, if you need it please let me know. I bet it's something small and silly, but I've been thumping at it for over two hours. Thanks in advance!

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What is the best Broadphase Interface for moving spheres?

- by Molmasepic

As of now I am working on optimizing the performance of the physics and collision, and as of now I am having some slowdowns on my other computers from my main. I have well over 3000 btSphereShape Rigidbodies and 2/3 of them do not move at all, but I am noticing(by the profile below) that collision is taking a bit of time to maneuver. Each sample counts as 0.01 seconds. % cumulative self self total time seconds seconds calls ms/call ms/call name 10.09 0.65 0.65 SphereTriangleDetector::collide(btVector3 const&, btVector3&, btVector3&, float&, float&, float) 7.61 1.14 0.49 btSphereTriangleCollisionAlgorithm::processCollision(btCollisionObject*, btCollisionObject*, btDispatcherInfo const&, btManifoldResult*) 5.59 1.50 0.36 btConvexTriangleCallback::processTriangle(btVector3*, int, int) 5.43 1.85 0.35 btQuantizedBvh::reportAabbOverlappingNodex(btNodeOverlapCallback*, btVector3 const&, btVector3 const&) const 4.97 2.17 0.32 btBvhTriangleMeshShape::processAllTriangles(btTriangleCallback*, btVector3 const&, btVector3 const&) const::MyNodeOverlapCallback::processNode(int, int) 4.19 2.44 0.27 btSequentialImpulseConstraintSolver::resolveSingleConstraintRowGeneric(btRigidBody&, btRigidBody&, btSolverConstraint const&) 4.04 2.70 0.26 btSequentialImpulseConstraintSolver::resolveSingleConstraintRowLowerLimit(btRigidBody&, btRigidBody&, btSolverConstraint const&) 3.73 2.94 0.24 Ogre::OctreeSceneManager::walkOctree(Ogre::OctreeCamera*, Ogre::RenderQueue*, Ogre::Octree*, Ogre::VisibleObjectsBoundsInfo*, bool, bool) 3.42 3.16 0.22 btTriangleShape::getVertex(int, btVector3&) const 2.48 3.32 0.16 Ogre::Frustum::isVisible(Ogre::AxisAlignedBox const&, Ogre::FrustumPlane*) const 2.33 3.47 0.15 1246357 0.00 0.00 Gorilla::Layer::setVisible(bool) 2.33 3.62 0.15 SphereTriangleDetector::getClosestPoints(btDiscreteCollisionDetectorInterface::ClosestPointInput const&, btDiscreteCollisionDetectorInterface::Result&, btIDebugDraw*, bool) 1.86 3.74 0.12 btCollisionDispatcher::findAlgorithm(btCollisionObject*, btCollisionObject*, btPersistentManifold*) 1.86 3.86 0.12 btSequentialImpulseConstraintSolver::setupContactConstraint(btSolverConstraint&, btCollisionObject*, btCollisionObject*, btManifoldPoint&, btContactSolverInfo const&, btVector3&, float&, float&, btVector3&, btVector3&) 1.71 3.97 0.11 btTriangleShape::getEdge(int, btVector3&, btVector3&) const 1.55 4.07 0.10 _Unwind_SjLj_Register 1.55 4.17 0.10 _Unwind_SjLj_Unregister 1.55 4.27 0.10 Ogre::D3D9HardwareVertexBuffer::updateBufferResources(char const*, Ogre::D3D9HardwareVertexBuffer::BufferResources*) 1.40 4.36 0.09 btManifoldResult::addContactPoint(btVector3 const&, btVector3 const&, float) 1.40 4.45 0.09 btSequentialImpulseConstraintSolver::setupFrictionConstraint(btSolverConstraint&, btVector3 const&, btRigidBody*, btRigidBody*, btManifoldPoint&, btVector3 const&, btVector3 const&, btCollisionObject*, btCollisionObject*, float, float, float) 1.24 4.53 0.08 btSequentialImpulseConstraintSolver::convertContact(btPersistentManifold*, btContactSolverInfo const&) 1.09 4.60 0.07 408760 0.00 0.00 Living::MapHide() 1.09 4.67 0.07 btSphereTriangleCollisionAlgorithm::~btSphereTriangleCollisionAlgorithm() 1.09 4.74 0.07 inflate_fast EDIT: Updated to show current Profile. I have only listed the functions using over 1% time from the many functions that are being used. Another thing is that each monster has a certain area that they stay in and are only active when a player is in said area. I was wondering if maybe there is a way to deactivate the non-active monsters from bullet(reactivating once in the area again) or maybe theres a different broadphase interface that I should use. The current BPI is btDbvtBroadphase. EDIT: Here is the Profile on the other computer(the top one is my main) Each sample counts as 0.01 seconds. % cumulative self self total time seconds seconds calls ms/call ms/call name 12.18 1.19 1.19 SphereTriangleDetector::collide(btVector3 const&, btVector3&, btVector3&, float&, float&, float) 6.76 1.85 0.66 btSphereTriangleCollisionAlgorithm::processCollision(btCollisionObject*, btCollisionObject*, btDispatcherInfo const&, btManifoldResult*) 5.83 2.42 0.57 btQuantizedBvh::reportAabbOverlappingNodex(btNodeOverlapCallback*, btVector3 const&, btVector3 const&) const 5.12 2.92 0.50 btConvexTriangleCallback::processTriangle(btVector3*, int, int) 4.61 3.37 0.45 btTriangleShape::getVertex(int, btVector3&) const 4.09 3.77 0.40 _Unwind_SjLj_Register 3.48 4.11 0.34 btBvhTriangleMeshShape::processAllTriangles(btTriangleCallback*, btVector3 const&, btVector3 const&) const::MyNodeOverlapCallback::processNode(int, int) 2.46 4.35 0.24 btSequentialImpulseConstraintSolver::resolveSingleConstraintRowLowerLimit(btRigidBody&, btRigidBody&, btSolverConstraint const&) 2.15 4.56 0.21 _Unwind_SjLj_Unregister 2.15 4.77 0.21 SphereTriangleDetector::getClosestPoints(btDiscreteCollisionDetectorInterface::ClosestPointInput const&, btDiscreteCollisionDetectorInterface::Result&, btIDebugDraw*, bool) 1.84 4.95 0.18 btTriangleShape::getEdge(int, btVector3&, btVector3&) const 1.64 5.11 0.16 btSequentialImpulseConstraintSolver::resolveSingleConstraintRowGeneric(btRigidBody&, btRigidBody&, btSolverConstraint const&) 1.54 5.26 0.15 btSequentialImpulseConstraintSolver::setupContactConstraint(btSolverConstraint&, btCollisionObject*, btCollisionObject*, btManifoldPoint&, btContactSolverInfo const&, btVector3&, float&, float&, btVector3&, btVector3&) 1.43 5.40 0.14 Ogre::D3D9HardwareVertexBuffer::updateBufferResources(char const*, Ogre::D3D9HardwareVertexBuffer::BufferResources*) 1.33 5.53 0.13 btManifoldResult::addContactPoint(btVector3 const&, btVector3 const&, float) 1.13 5.64 0.11 btRigidBody::predictIntegratedTransform(float, btTransform&) 1.13 5.75 0.11 btTriangleIndexVertexArray::getLockedReadOnlyVertexIndexBase(unsigned char const**, int&, PHY_ScalarType&, int&, unsigned char const**, int&, int&, PHY_ScalarType&, int) const 1.02 5.85 0.10 btSphereTriangleCollisionAlgorithm::CreateFunc::CreateCollisionAlgorithm(btCollisionAlgorithmConstructionInfo&, btCollisionObject*, btCollisionObject*) 1.02 5.95 0.10 btSphereTriangleCollisionAlgorithm::btSphereTriangleCollisionAlgorithm(btPersistentManifold*, btCollisionAlgorithmConstructionInfo const&, btCollisionObject*, btCollisionObject*, bool) Edited same as other Profile.

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Retrieving model position after applying modeltransforms in XNA

- by Glen Dekker

For this method that the goingBeyond XNA tutorial provides, it would be really convenient if I could retrieve the new position of the model after I apply all the transforms to the mesh. I have edited the method a little for what I need. Does anyone know a way I can do this? public void DrawModel( Camera camera ) { Matrix scaleY = Matrix.CreateScale(new Vector3(1, 2, 1)); Matrix temp = Matrix.CreateScale(100f) * scaleY * rotationMatrix * translationMatrix * Matrix.CreateRotationY(MathHelper.Pi / 6) * translationMatrix2; Matrix[] modelTransforms = new Matrix[model.Bones.Count]; model.CopyAbsoluteBoneTransformsTo(modelTransforms); if (camera.getDistanceFromPlayer(position+position1) > 3000) return; foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.World = modelTransforms[mesh.ParentBone.Index] * temp * worldMatrix; effect.View = camera.viewMatrix; effect.Projection = camera.projectionMatrix; } mesh.Draw(); } }

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Strange mesh import problem with Assimp and OpenGL

- by Morgan

Using the assimp library for importing 3D data into an OpenGL application. I get some strange problems regarding indexing of the vertices: If I use the following code for importing vertex indices: for (unsigned int t = 0; t < mesh->mNumFaces; ++t) { const struct aiFace * face = &mesh->mFaces[t]; if (face->mNumIndices == 3) { indices->push_back(face->mIndices[0]); indices->push_back(face->mIndices[1]); indices->push_back(face->mIndices[2]); } } I get the following result: Instead, if I use the following code: for(int k = 0; k < 2 ; k++) { for (unsigned int t = 0; t < mesh->mNumFaces; ++t) { const struct aiFace * face = &mesh->mFaces[t]; if (face->mNumIndices == 3) { indices->push_back(face->mIndices[0]); indices->push_back(face->mIndices[1]); indices->push_back(face->mIndices[2]); } } } I get the correct result: Hence adding the indices twice, renders the correct result? The OpenGL buffer is populated, like so: glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices->size() * sizeof(unsigned int), indices->data(), GL_STATIC_DRAW); And rendered as follows: glDrawElements(GL_TRIANGLES, vertexCount*3, GL_UNSIGNED_INT, indices->data());

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Fog shader camera problem

- by MaT

I have some difficulties with my vertex-fragment fog shader in Unity. I have a good visual result but the problem is that the gradient is based on the camera's position, it moves as the camera moves. I don't know how to fix it. Here is the shader code. struct v2f { float4 pos : SV_POSITION; float4 grabUV : TEXCOORD0; float2 uv_depth : TEXCOORD1; float4 interpolatedRay : TEXCOORD2; float4 screenPos : TEXCOORD3; }; v2f vert(appdata_base v) { v2f o; o.pos = mul(UNITY_MATRIX_MVP, v.vertex); o.uv_depth = v.texcoord.xy; o.grabUV = ComputeGrabScreenPos(o.pos); half index = v.vertex.z; o.screenPos = ComputeScreenPos(o.pos); o.interpolatedRay = mul(UNITY_MATRIX_MV, v.vertex); return o; } sampler2D _GrabTexture; float4 frag(v2f IN) : COLOR { float3 uv = UNITY_PROJ_COORD(IN.grabUV); float dpth = UNITY_SAMPLE_DEPTH(tex2Dproj(_CameraDepthTexture, uv)); dpth = LinearEyeDepth(dpth); float4 wsPos = (IN.screenPos + dpth * IN.interpolatedRay); // Here is the problem but how to fix it float fogVert = max(0.0, (wsPos.y - _Depth) * (_DepthScale * 0.1f)); fogVert *= fogVert; fogVert = (exp (-fogVert)); return fogVert; } Thanks a lot !

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Smarphone Apps. music, licenses and fees .. nightmare

- by mm24

I have recently asked a question about music in games like Guitar Hero. I have found that that in Europe (at least) if I do want to use a track composed by a musician member of a royalty collecting society I need to pay a flat fee to the society and not only to the member. So a "one-to-one" agreement is not valid and the society can come up to me and ask me for money for each download. Even if for FREE! This is a fee sheet list of the UK agency: for fee, see "Permanent download services" It is about 1,200 GBP for less than 22,000 copies and they DON'T specify anything more and they said me on the phone that I need to wait and see how many downloads I get before knowing the price. This is kind of crazy as If I give away the App for free I will have to PAY 1,200 GBP!! I am shocked and I feel very bad. One agency suggested me to use a fake name of the artist, but in this way is not fair to my collaborators as what they hope is that the App gets lots of downloads and in this way that other people will get to know about them and hopefully commission them more work. The other solution is to work only with non registered musicians. The question here to you is.. has anyone found a legal way to do use music from registered authors in a game?

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Convert rotation from Right handed System to left handed

- by Hector Llanos

I have Euler angles from a right handed system that I am trying to convert to a left handed system. All the information that I have read online says that to convert it simply multiply the axis and the angle in the correct order and it should work. In other words, Z * Y * X. When I do this what I see in Maya, and in engine still do not match up. This is what I have so far: static Quaternion ConvertToRightHand(Vector3 Euler) { Quaternion x = Quaternion.AngleAxis(-Euler.x, Vector3.right); Quaternion y = Quaternion.AngleAxis(Euler.y, Vector3.up); Quaternion z = Quaternion.AngleAxis(Euler.z, Vector3.forward); return (z * y * x); } Keeping the -Euler.x helps keep the object pointing up correctly, but when I pass ( 0,0,0) to face in the -z, it faces in the +z. Help :/

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Strange if-else branching behavior in a fragment shader

- by Winged

In my fragment shader I have passed an uniform int uLightType variable, which indicates what type of light is in usage right now. The problem is that if-else branching does not work correctly - the fragment shader performs instructions in every if statement block. if (uLightType == 1) { // Spotlight light type vec3 depthTextureCoord = vDepthPosition.xyz / vDepthPosition.w; shadowDepth = unpack(texture2D(uDepthMapSampler, depthTextureCoord.xy)); } else if (uLightType == 2) { // Omni-directional light type shadowDepth = unpack(textureCube(uDepthCubemapSampler, -lightVec)); } In the case when uLightType equals 1, unless I comment out the content of the second if block, it assigns an another value to shadowDepth. Also while uLightType equals 1, when I remove the second 'if' block and change == to != like in the sample code below, nothing happens (which means that uLightType really equals 1). if (uLightType != 1) { // Spotlight light type vec3 depthTextureCoord = vDepthPosition.xyz / vDepthPosition.w; shadowDepth = unpack(texture2D(uDepthMapSampler, depthTextureCoord.xy)); } Also, when I manually create an int variable (which is not an uniform) like this: var lightType = 1; and replace uLightType with it in the if-else branch, everything works fine, so I guess it have something to do with the fact that uLightType is the uniform.

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Dynamic/Adaptive RLE

- by Lucius

So, I'm developing a 2D, tile based game and a map maker thingy - all in Java. The problem is that recently I've been having some memory issues when about 4 maps are loaded. Each one of these maps are composed of 128x128 tiles and have 4 layers (for details and stuff). I already spent a good amount of time searching for solutions and the best thing I found was run-length enconding (RLE). It seems easy enough to use with static data, but is there a way to use it with data that is constantly changing, without a big drop in performance? In my maps, supposing I'm compressing the columns, I would have 128 rows, each with some amount of data (hopefully less than it would be without RLE). Whenever I change a tile, that whole row would have to be checked and I'm affraid that would slow down too much the production (and I'm in a somewhat tight schedule). Well, worst case scenario I work on each map individually, and save them using RLE, but it would be really nice if I could avoind that. EDIT: What I'm currently using to store the data for the tiles is a 2D array of HashMaps that use the layer as key and store the id of the tile in that position - like this: private HashMap< Integer, Integer [][]

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changing body type without change of center of mass

- by philipp

I have an box2d project with some bodies in it, which move around without any user interaction. But if the user selects one of the bodies, he should be able to move it around just like he wants to. To keep it short, I want to change the type of the body to "kinematic" while the user controls it and back to "dynamic" afterwards. If I do so the rotation center of the body changes with the change of the type. How can I reset this? The body's fixture is created of a single b2PolygonShape, with its vertices set via SetAsArray(). Greetings philipp EDIT:: So I looked around about setting the local center of bodies. what brought me to this solution: var md = new b2MassData(); this.body.GetMassData( md ); this.body.SetType( b2body.b2_kinematicBody ); this.body.SetMassData( md ); that did not work, so I had a look at the source and found that SetMassData() always returns if the body is not "dynamic". So I tried this: var md = new b2MassData(); this._body.GetMassData( md ); this._body.SetType( b2Body.b2_kinematicBody ); this._body.m_sweep.localCenter.Set( md.center.x, md.center.y ); what actually is modifying the private data of the body. But it works and no errors appear, but can I really do this without the risk of breaking the application, or in other words, under which circumstances could this solution might cause errors? n.b.: I am using box2dweb of the latest release. Greetings philipp

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How can I test if an oriented rectangle contains another oriented rectangle?

- by gronzzz

I have the following situation: To detect whether is the red rectangle is inside orange area I use this function: - (BOOL)isTile:(CGPoint)tile insideCustomAreaMin:(CGPoint)min max:(CGPoint)max { if ((tile.x < min.x) || (tile.x > max.x) || (tile.y < min.y) || (tile.y > max.y)) { NSLog(@" Object is out of custom area! "); return NO; } return YES; } But what if I need to detect whether the red tile is inside of the blue rectangle? I wrote this function which uses the world position: - (BOOL)isTileInsidePlayableArea:(CGPoint)tile { // get world positions from tiles CGPoint rt = [[CoordinateFunctions shared] worldFromTile:ccp(24, 0)]; CGPoint lb = [[CoordinateFunctions shared] worldFromTile:ccp(24, 48)]; CGPoint worldTile = [[CoordinateFunctions shared] worldFromTile:tile]; return [self isTile:worldTile insideCustomAreaMin:ccp(lb.x, lb.y) max:ccp(rt.x, rt.y)]; } How could I do this without converting to the global position of the tiles?

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Game programming course materials: What should it include?

- by Esa

I am tasked to create the course materials for a game programming class, and I’d like your opinion on what aspects and areas of game programming, such as game state management, game object storing or simple AI, should I include in it? The course is intented to be the first step into game programming for students with novice skills in programming. There will be mathematics as well, but I found that there are multiple questions, with good answers, on that subject already.

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OpenGL not rendering my images to the screen

- by Brendan Webster

for some reason my game isn't showing the image I am rendering to the screen. My engine is state based, and at the beginning I set the logo, but it isn't showing on the screen. Here is my method of doing so first I create one image and assign some values to it's preset values. //create one image instance for the logo background O_File.v_Create_Images(1); //set the atributes of the background //first Image O_File.sImage[0].nImageDepth = -30.0f; O_File.sImage[0].sImageLocation = "image.bmp"; //load the images int O_File.v_Load_Images(); Then I load them with DevIL void C_File_Manager::v_Load_Images() { ilGenImages(1, &image); ilBindImage(image); for(int i = 0;i < sImage.size();i++) { success = ilLoadImage(sImage[i].sImageLocation.c_str()); if (success) { success = ilConvertImage(IL_RGBA, IL_UNSIGNED_BYTE); glGenTextures(1, &image); glBindTexture(GL_TEXTURE_2D, image); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, 4, ilGetInteger(IL_IMAGE_WIDTH), ilGetInteger(IL_IMAGE_HEIGHT), 0, ilGetInteger(IL_IMAGE_FORMAT), GL_UNSIGNED_BYTE, ilGetData()); //asign values to the width and height of the image if they are already not assigned if(sImage[i].nImageHeight == 0) sImage[i].nImageHeight = ilGetInteger(IL_IMAGE_HEIGHT); if(sImage[i].nImageWidth == 0) sImage[i].nImageWidth = ilGetInteger(IL_IMAGE_WIDTH); std::cout << sImage[i].nImageHeight << std::endl; const std::string word = sImage[i].sImageLocation.c_str(); std::cout << sImage[i].sImageLocation.c_str() << std::endl; ilLoadImage(word.c_str()); ilDeleteImages(1, &image); } } } and then I apply them to the screen void C_File_Manager::v_Apply_Images() { glMatrixMode(GL_MODELVIEW); glLoadIdentity(); for(int i = 0;i < sImage.size();i++) { //move the image to where it should be on the screen; glTranslatef(sImage[i].nImageX,sImage[i].nImageY,sImage[i].nImageDepth); //rotate image around the 3 axes glRotatef(sImage[i].fImageAngleX,1,0,0); glRotatef(sImage[i].fImageAngleY,0,1,0); glRotatef(sImage[i].fImageAngleZ,0,0,1); //scale the image glScalef(1,1,1); //center the image glTranslatef((sImage[i].nImageWidth/2),(sImage[i].nImageHeight/2),0); //draw the box that will encase the loaded image glBegin(GL_QUADS); //change the color of the loaded image; glColor4f(1,1,1,1); //top left corner of image glNormal3f(0.0,0,0.0); glTexCoord2f (1.0, 0.0); glVertex3f(0,0,sImage[i].nImageDepth); //top right corner of image glNormal3f(1.0,0,0.0); glTexCoord2f (1.0, 1.0); glVertex3f(0,sImage[i].nImageHeight,sImage[i].nImageDepth); //bottom right corner of image glNormal3f(-1.0,0,0.0); glTexCoord2f (0.0, 1.0); glVertex3f(sImage[i].nImageWidth,sImage[i].nImageHeight,sImage[i].nImageDepth); //bottom left corner of image glNormal3f(-1.0,0,0.0); glTexCoord2f(0.0, 0.0); glVertex3f(sImage[i].nImageWidth,0,sImage[i].nImageDepth); glEnd(); } } when I debug there is no errors at all, but yet the images don't show up on the screen, I have positioned the camera at (0,0,-1) and that is where the images should show up. the clipping plane is set 1 to 1000. There is probably some random problem with the code, but I just can't catch it.

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Game window systems and internal frames

- by 2080

I don't know if this is a valid question, but: What kind of window manager do games use which have internal frames (Frames inside frames)? Does this differ between the programming languages (Are e.g. in Java the AWT/Swing libraries used to manage these and other graphical elements, such as buttons,or is this to restrictive (speed, graphical possibilities?)) A special example would be EVE Online, where the client can use the ingame windows like on a normal desktop.

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How to implement efficient Fog of War?

- by Cambrano

I've asked a question how to implement Fog Of War(FOW) with shaders. Well I've got this working. I use the vertex color to identify the alpha of a single vertex. I guess the most of you know what the FOW of Age of Empires was like, anyway I'll shortly explain it: You have a map. Everything is unexplored(solid black / 100% transparency) at the beginning. When your NPC's / other game units explore the world (by moving around mostly) they unshadow the map. That means. Everything in a specific radius (viewrange) around a NPC is visible (0%transparency). Anything that is out of viewrange but already explored is visible but shadowed (50% transparency). So yeah, AoE had relatively huge maps. Requirements was something around 100mhz etc. So it should be relatively easy to implement something to solve this problem - actually. Okay. I'm currently adding planes above my world and set the color per vertex. Why do I use many planes ? Unity has a vertex limit of 65.000 per mesh. According to the size of my tiles and the size of my map I need more than one plane. So I actually need a lot of planes. This is obviously pita for my FPS. Well so my question is, what are simple (in sense of performance) techniques to implement a FOW shader? Okay some simplified code what I'm doin so far: // Setup for (int x = 0; x < (Map.Dimension/planeSize); x++) { for (int z = 0; z < (Map.Dimension/planeSize); z++) { CreateMeshAt(x*planeSize, 3, z*planeSize) } } // Explore (is called from NPCs when walking for example) for (int x = ((int) from.x - radius); x < from.x + radius; x ++) { for (int z = ((int) from.z - radius); z < from.z + radius; z ++) { if (from.Distance(x, 1, z) > radius) continue; _transparency[x/tileSize, z/tileSize] = 0.5f; } } // Update foreach(GameObject plane in planes){ foreach(Vector3 vertex in vertices){ Vector3 worldPos = GetWorldPos(vertex); vertex.Color = new Color(0,0,0, _transparency[worldPos.x/tileSize, worldPos.z/tileSize]); } } My shader just sets the transparency of the vertex now, which comes from the vertex color channel

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Xna Equivalent of Viewport.Unproject in a draw call as a matrix transformation

- by Nick Crowther

I am making a 2D sidescroller and I would like to draw my sprite to world space instead of client space so I do not have to lock it to the center of the screen and when the camera stops the sprite will walk off screen instead of being stuck at the center. In order to do this I wanted to make a transformation matrix that goes in my draw call. I have seen something like this: http://stackoverflow.com/questions/3570192/xna-viewport-projection-and-spritebatch I have seen Matrix.CreateOrthographic() used to go from Worldspace to client space but, how would I go about using it to go from clientspace to worldspace? I was going to try putting my returns from the viewport.unproject method I have into a scale matrix such as: blah = Matrix.CreateScale(unproject.X,unproject.Y,0); however, that doesn't seem to work correctly. Here is what I'm calling in my draw method(where X is the coordinate my camera should follow): Vector3 test = screentoworld(X, graphics); var clienttoworld = Matrix.CreateScale(test.X,test.Y, 0); animationPlayer.Draw(theSpriteBatch, new Vector2(X.X,X.Y),false,false,0,Color.White,new Vector2(1,1),clienttoworld); Here is my code in my unproject method: Vector3 screentoworld(Vector2 some, GraphicsDevice graphics): Vector2 Position =(some.X,some.Y); var project = Matrix.CreateOrthographic(5*graphicsdevice.Viewport.Width, graphicsdevice.Viewport.Height, 0, 1); var viewMatrix = Matrix.CreateLookAt( new Vector3(0, 0, -4.3f), new Vector3(X.X,X.Y,0), Vector3.Up); //I have also tried substituting (cam.Position.X,cam.Position.Y,0) in for the (0,0,-4.3f) Vector3 nearSource = new Vector3(Position, 0f); Vector3 nearPoint = graphicsdevice.Viewport.Unproject(nearSource, project, viewMatrix, Matrix.Identity); return nearPoint;

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Making game constants/tables available to game logic classes/routines in a modular manner

- by Extrakun

Suppose I have a game where there are several predefined constants and charts (a XP chart, cost of goods and so on). Those could be defined at runtime, or load from files at start-up. The question is how should those logic routines access the constants and charts? For example, I could try using global variables, but that cause all classes relying on the variables to be tightly coupled with them.

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Can't use the hardware scissor any more, should I use the stencil buffer or manually clip sprites?

- by Alex Ames

I wrote a simple UI system for my game. There is a clip flag on my widgets that you can use to tell a widget to clip any children that try to draw outside their parent's box (for scrollboxes for example). The clip flag uses glScissor, which is fed an axis aligned rectangle. I just added arbitrary rotation and transformations to my widgets, so I can rotate or scale them however I want. Unfortunately, this breaks the scissor that I was using as now my clip rectangle might not be axis aligned. There are two ways I can think of to fix this: either by using the stencil buffer to define the drawable area, or by having a wrapper function around my sprite drawing function that will adjust the vertices and texture coords of the sprites being drawn based on the clipper on the top of a clipper stack. Of course, there may also be other options I can't think of (something fancy with shaders possibly?). I'm not sure which way to go at the moment. Changing the implementation of my scissor functions to use the stencil buffer probably requires the smallest change, but I'm not sure how much overhead that has compared to the coordinate adjusting or if the performance difference is even worth considering.

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2D Planet Gravity

- by baked

I'm trying to make a simple game where a spaceship is launched and then its path is effected by the gravity of planets. Similar to this game: http://sciencenetlinks.com/interactives/gravity.html I wish to know how to replicate the effect the planets have on the spaceship in this game so a spaceship can 'loop' around a planet to change direction. I have managed to achieve some bogus results where the spaceship loops in a huge ellipse around the planet or is only slightly affected by the gravity of a planet using Vectors. Thanks in advance. p.s I have plenty of coding experience just none to do with game dev.

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Django and Google App Engine Helper not finding the ipaddr module.

- by Phil

I'm trying to get Django running on GAE using this tutorial. When I run python manage.py runserver I get the stacktrace below. I'm new to both django and python so I don't know what my next steps are (This is Ubuntu Jaunty btw). It seems django isn't finding the GAE module ipaddr which comes with SDK 1.3.1. How do I get django to find this module? /home/username/bin/google_appengine/google/appengine/api/datastore_file_stub.py:40: DeprecationWarning: the md5 module is deprecated; use hashlib instead import md5 /home/username/bin/google_appengine/google/appengine/api/memcache/__init__.py:31: DeprecationWarning: the sha module is deprecated; use the hashlib module instead import sha Traceback (most recent call last): File "manage.py", line 18, in <module> InstallAppengineHelperForDjango() File "/home/username/Development/GAE/myapp/appengine_django/__init__.py", line 543, in InstallAppengineHelperForDjango InstallDjangoModuleReplacements() File "/home/username/Development/GAE/myapp/appengine_django/__init__.py", line 260, in InstallDjangoModuleReplacements import django.db File "/home/username/Development/GAE/myapp/django/db/__init__.py", line 57, in <module> 'TIME_ZONE': settings.TIME_ZONE, File "/home/username/Development/GAE/myapp/appengine_django/db/base.py", line 117, in __init__ self._setup_stubs() File "/home/username/Development/GAE/myapp/appengine_django/db/base.py", line 128, in _setup_stubs from google.appengine.tools import dev_appserver_main File "/home/username/bin/google_appengine/google/appengine/tools/dev_appserver_main.py", line 82, in <module> from google.appengine.tools import appcfg File "/home/username/bin/google_appengine/google/appengine/tools/appcfg.py", line 53, in <module> from google.appengine.api import dosinfo File "/home/username/bin/google_appengine/google/appengine/api/dosinfo.py", line 25, in <module> import ipaddr ImportError: No module named ipaddr

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