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• How do you calculate UVW coordinates?

  - by Jenko

  I'm working on a 3d engine and I'm calculating UVT coordinates, where U and V represent pixels on the texture measured in 0-1, and T is: T = perspective / Z But I'm trying to use this perspective-correct triangle rasteriser, which requires a W, per vertex. How do I calculate the W for each vertex for the drawPerspectiveTexturedPolygon() function? Hint: The code comments refer to W as the "homogenous coordinate" ... does that mean anything?

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• How should an object that uses composition set its composed components?

  - by Casey

  After struggling with various problems and reading up on component-based systems and reading Bob Nystrom's excellent book "Game Programming Patterns" and in particular the chapter on Components I determined that this is a horrible idea: //Class intended to be inherited by all objects. Engine uses Objects exclusively. class Object : public IUpdatable, public IDrawable { public: Object(); Object(const Object& other); Object& operator=(const Object& rhs); virtual ~Object() =0; virtual void SetBody(const RigidBodyDef& body); virtual const RigidBody* GetBody() const; virtual RigidBody* GetBody(); //Inherited from IUpdatable virtual void Update(double deltaTime); //Inherited from IDrawable virtual void Draw(BITMAP* dest); protected: private: }; I'm attempting to refactor it into a more manageable system. Mr. Nystrom uses the constructor to set the individual components; CHANGING these components at run-time is impossible. It's intended to be derived and be used in derivative classes or factory methods where their constructors do not change at run-time. i.e. his Bjorne object is just a call to a factory method with a specific call to the GameObject constructor. Is this a good idea? Should the object have a default constructor and setters to facilitate run-time changes or no default constructor without setters and instead use a factory method? Given: class Object { public: //...See below for constructor implementation concerns. Object(const Object& other); Object& operator=(const Object& rhs); virtual ~Object() =0; //See below for Setter concerns IUpdatable* GetUpdater(); IDrawable* GetRenderer(); protected: IUpdatable* _updater; IDrawable* _renderer; private: }; Should the components be read-only and passed in to the constructor via: class Object { public: //No default constructor. Object(IUpdatable* updater, IDrawable* renderer); //...remainder is same as above... }; or Should a default constructor be provided and then the components can be set at run-time? class Object { public: Object(); //... SetUpdater(IUpdater* updater); SetRenderer(IDrawable* renderer); //...remainder is same as above... }; or both? class Object { public: Object(); Object(IUpdater* updater, IDrawable* renderer); //... SetUpdater(IUpdater* updater); SetRenderer(IDrawable* renderer); //...remainder is same as above... };

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• How to evaluate a user against optimal performance?

  - by Alex K

  I have trouble coming up with a system of assigning a rating to player's performance. Well, technically there is is a trivial rating system, but I don't like it because it would mean assigning negative scores, which I think most players will be discouraged by. The problem is that I only know the ideal number of actions to get the desired result. The worst case is infinite number of actions, so there is no obvious scale. The trivial way I referred to above is to take score = (#optimal-moves - #players-moves), with ideal score being zero. However, psychologically people like big numbers. No one wants to win by getting a mark of 0. I wonder if there is a system that someone else has come up with before to solve this problem? Essentially I wish to score the players based on: How close they've come to the ideal solution. Different challenges will have different optimal number of actions, so the scoring system needs to take that into account, e.g. Challenge 1 - max 10 points, Challenge 2 - max 20 points. I don't mind giving the players negative scores if they've performed exceptionally badly, I just don't want all scores to be <=0

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• Monogame - Input secuence game (Scripting?)

  - by user2662567

  I'm starting to program my very first game, it's a clone of DDR/Stepmania done for research purposes and learning. I (at this early stage) get most of the UI/Music/input work that should be done, but what i still can't grasp is scripting, i've read about Lua and that you shouldn't use it with XNA/Monogame as C# is capable enough, but i cannot get the utility of it. Assuming the needs of my game, ¿What would be the ideal way to implement the input secuences it needs?, i thought of XML/Json, let's say Stage 1 <game> <level id="1"> <step id="1" key="up" time="00:00:01"/> <step id="2" key="left" time="00:00:02"/> </level> </game> Is that a correct implementation? or are there better ways with more benefits?

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• Problems implementing a screen space shadow ray tracing shader

  - by Grieverheart

  Here I previously asked for the possibility of ray tracing shadows in screen space in a deferred shader. Several problems were pointed out. One of the most important problem is that only visible objects can cast shadows and objects between the camera and the shadow caster can interfere. Still I thought it'd be a fun experiment. The idea is to calculate the view coordinates of pixels and cast a ray to the light. The ray is then traced pixel by pixel to the light and its depth is compared with the depth at the pixel. If a pixel is in front of the ray, a shadow is casted at the original pixel. At first I thought that I could use the DDA algorithm in 2D to calculate the distance 't' (in p = o + t d, where o origin, d direction) to the next pixel and use it in the 3D ray equation to find the ray's z coordinate at that pixel's position. For the 2D ray, I would use the projected and biased 3D ray direction and origin. The idea was that 't' would be the same in both 2D and 3D equations. Unfortunately, this is not the case since the projection matrix is 4D. Thus, some tweak needs to be done to make this work this way. I would like to ask if someone knows of a way to do what I described above, i.e. from a 2D ray in texture coordinate space to get the 3D ray in screen space. I did implement a simple version of the idea which you can see in the following video: video here Shadows may seem a bit pixelated, but that's mostly because of the size of the step in 't' I chose. And here is the shader: #version 330 core uniform sampler2D DepthMap; uniform vec2 projAB; uniform mat4 projectionMatrix; const vec3 light_p = vec3(-30.0, 30.0, -10.0); noperspective in vec2 pass_TexCoord; smooth in vec3 viewRay; layout(location = 0) out float out_AO; vec3 CalcPosition(void){ float depth = texture(DepthMap, pass_TexCoord).r; float linearDepth = projAB.y / (depth - projAB.x); vec3 ray = normalize(viewRay); ray = ray / ray.z; return linearDepth * ray; } void main(void){ vec3 origin = CalcPosition(); if(origin.z < -60) discard; vec2 pixOrigin = pass_TexCoord; //tex coords vec3 dir = normalize(light_p - origin); vec2 texel_size = vec2(1.0 / 600.0); float t = 0.1; ivec2 pixIndex = ivec2(pixOrigin / texel_size); out_AO = 1.0; while(true){ vec3 ray = origin + t * dir; vec4 temp = projectionMatrix * vec4(ray, 1.0); vec2 texCoord = (temp.xy / temp.w) * 0.5 + 0.5; ivec2 newIndex = ivec2(texCoord / texel_size); if(newIndex != pixIndex){ float depth = texture(DepthMap, texCoord).r; float linearDepth = projAB.y / (depth - projAB.x); if(linearDepth > ray.z + 0.1){ out_AO = 0.2; break; } pixIndex = newIndex; } t += 0.5; if(texCoord.x < 0 || texCoord.x > 1.0 || texCoord.y < 0 || texCoord.y > 1.0) break; } } As you can see, here I just increment 't' by some arbitrary factor, calculate the 3D ray and project it to get the pixel coordinates, which is not really optimal. Hopefully, I would like to optimize the code as much as possible and compare it with shadow mapping and how it scales with the number of lights. PS: Keep in mind that I reconstruct position from depth by interpolating rays through a full screen quad.

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• Making a 2D game with responsive resolution

  - by alexandervrs

  I am making a 2D game, however I wish for it to be resolution agnostic. My target resolution i.e. where things look as intended is 1600 x 900. My ideas are: Make the HUD stay fixed to the sides no matter what resolution, use different size for HUD graphics under a certain resolution and another under a certain large one. Use large HD PNG sprites/backgrounds which are a power of 2, so they scale nicely. No vectors. Use the player's native resolution. Scale the game area (not the HUD) to fit (resulting zooming in some and cropping the game area sides if necessary for widescreen, no stretch), but always fill the screen. Have a min and max resolution limit for small and very large displays where you will just change the resolution(?) or scale up/down to fit. What I am a bit confused though is what math formula I would use to scale the game area correctly based on the resolution no matter the aspect ratio, fully fit in a square screen and with some clip to the sides for widescreen. Pseudocode would help as well. :)

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• 3D texture coordinates for a cube

  - by Roshan

  I want to use glTexImage3D with cube. what will be the texture coordinates for it? i am using GL_TEXTURE_3D as target. I tried with u v coordinates same as 2d texture coordinates with z component 0-depth for each face. But that goes wrong. How to apply each layer to each face of the cube with target= GL_TEXTURE_3D? Lets assume i have 8 layers of 2D images in my 3D texture. I want all 8 layers to apply on each of the cube and not 1 layer on 1 face of the cube.

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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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• 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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• How do you turn a cube into a sphere?

  - by Tom Dalling

  I'm trying to make a quad sphere based on an article, which shows results like this: I can generate a cube correctly: But when I convert all the points according to this formula (from the page linked above): x = x * sqrtf(1.0 - (y*y/2.0) - (z*z/2.0) + (y*y*z*z/3.0)); y = y * sqrtf(1.0 - (z*z/2.0) - (x*x/2.0) + (z*z*x*x/3.0)); z = z * sqrtf(1.0 - (x*x/2.0) - (y*y/2.0) + (x*x*y*y/3.0)); My sphere looks like this: As you can see, the edges of the cube still poke out too far. The cube ranges from -1 to +1 on all axes, like the article says. Any ideas what is wrong?

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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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• How to optimize collision detection

  - by Niklas

  I am developing a 2D Java Game with LibGDX. This is what it kinda looks like (simplified): The big black circle is the player, which you can move by tilting the smartphone. The red circles and blue rectangles are enemies, which will move from the right of the screen to the left. The player has to avoid crashing into them. Right now I am checking in the Game Loop every enemy against the player, whether they collide or not. This seems kinda inefficient to me, but I don't know how to improve it. I have tried the Quadtree approach, but it did not really work. The player could easily glitch through enemies and the collision was not detected. Unfortunately, I have destroyed the Quadtree implementation. I used this [tutorial/blog] as my Quadtree implementation(http://gamedevelopment.tutsplus.com/tutorials/quick-tip-use-quadtrees-to-detect-likely-collisions-in-2d-space--gamedev-374).

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• Is there any existing (old) game that released graphic as free or open source?

  - by Alexey Petrushin

  I'd like to (re)create an online version (html5/JS) of some old game, for example something like HoM&M 2. Maybe, some of old games were released as free or open source (I'm interested in the graphical assets only)? I heard something about Red Alert been released as free, but I'm not sure if it's permitted to reuse graphical assets in such manner. Do You know such games? Another question - can You please share Your thoughts, rough estimate - how much it will cost to pay an artist to create graphics similar to HoM&M 2?

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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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• How to make a ball fall faster on a ramp?

  - by Timothy Williams

  So, I'm making a ball game. Where you pick up the ball, drop it on a ramp, and it flies off in to blocks. The only problem right now is it falls at a normal speed, then lightly falls off, not nearly fast enough to get over the wall and hit the blocks. Is there any way to make the ball go faster down the ramp? Maybe even make it go faster depending on what height you dropped it from (e.g. if you hold it way above the ramp, and drop it, it will drop faster than if you dropped it right above the ramp.)

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• Drawing lines in 3D space

  - by DeadMG

  When attempting to draw a line in 3D space with D3DPT_LINELIST, then Direct3D gives me an error about an invalid vertex declaration, saying that it cannot be converted to an FVF. I am using the same vertex declaration and shader/stream setup as for my D3DPT_TRIANGLELIST rendering which works absolutely correctly. How can I use D3DPT_LINELIST to render some lines in 3D space? Edit: Oopsie, forgot my codeses. Here's my raw Draw call. D3DCALL(device->SetStreamSource(1, PerBoneBuffer.get(), 0, sizeof(PerInstanceData))); D3DCALL(device->SetStreamSourceFreq(1, D3DSTREAMSOURCE_INSTANCEDATA | 1)); D3DCALL(device->SetStreamSource(0, LineVerts, 0, sizeof(D3DXVECTOR3))); D3DCALL(device->SetStreamSourceFreq(0, D3DSTREAMSOURCE_INDEXEDDATA | lines.size())); D3DCALL(device->SetIndices(LineIndices)); PerInstanceData* data; std::vector<Wide::Render::Line*> lines_vec(lines.begin(), lines.end()); D3DCALL(PerBoneBuffer->Lock(0, lines.size() * sizeof(PerInstanceData), reinterpret_cast<void**>(&data), D3DLOCK_DISCARD)); std::for_each(lines.begin(), lines.end(), [&](Wide::Render::Line* ptr) { data->Color = D3DXColor(ptr->Colour); D3DXMATRIXA16 Translate, Scale, Rotate; D3DXMatrixTranslation(&Translate, ptr->Start.x, ptr->Start.y, ptr->Start.z); D3DXMatrixScaling(&Scale, ptr->Scale, 1, 1); D3DXMatrixRotationQuaternion(&Rotate, &D3DQuaternion(ptr->Rotation)); data->World = Scale * Rotate * Translate; }); D3DCALL(PerBoneBuffer->Unlock()); D3DCALL(device->DrawIndexedPrimitive(D3DPRIMITIVETYPE::D3DPT_LINELIST, 0, 0, 2, 0, 1)); Here's my vertex declaration: D3DVERTEXELEMENT9 BasicMeshVertices[] = { {0, 0, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_POSITION, 0}, {1, 0, D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 0}, {1, 16, D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 1}, {1, 32, D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 2}, {1, 48, D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 3}, {1, 64, D3DDECLTYPE_FLOAT4, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_COLOR, 0}, D3DDECL_END() }; The LineIndices are just 0, 1 and the LineVerts are just {0,0,0} and {1,0,0}, to represent a unit 3D line along the X axis.

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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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• 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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• Dynamic Environment Creation

  - by Jack

  I was wondering, I'm thinking on a more small-scale, abstracted level, but how does one create a dynamic environment a la Minecraft? In specific, I'm thinking of the world as a 3 dimensional array of block objects, how is it made so that large features such as oceans are created? The language isn't important, I'm thinking on a conceptual level, but if it helps, I use C# or C++. Thanks for any help!

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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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• 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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• Greiner-Hormann clipping problem

  - by Belgin

  I have a set of planar polygons in 3D space defined by their vertices in counterclockwise order. Let's define the 'positive face' as being the face of the 3D polygon such as when observed, the vertices appear in counterclockwise order, and the 'negative face', the face which when observed, the vertices appear in clockwise order. I'm doing perspective projection of the set of polygons onto a projection polygon defined by the points in this order: (0, h, 0), (0, 0, 0), (w, 0, 0), and (w, h, 0), where w and h are strictly positive integers. The positive face of this projection polygon is oriented towards positive Z, and the camera point is somewhere at (0, 0, d), where d is a strictly negative number. In order to 'clip' the projected polygons into the projection polygon, I'm applying the Greiner-Hormann (PDF) clipping algorithm, which requires that the clipper and the to-be-clipped polygons be in the same order (i.e. clockwise or counterclockwise). My question is the following: How can I determine whether the projected face of the 3D polygon is the negative or the positive one? Meaning, how do I find out if I have to work with the vertices in normal or inverted order for the algorithm to work? I noticed that only if the 3D polygon is facing the projection polygon with its negative face, both of them are in the same order (counterclockwise), otherwise, a modification needs to be done. Here is a picture (PNG) that illustrates this. Note that the planes described by the polygon from the set and the projection polygon may not always be parallel.

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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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• Any good C++ Component/Entity frameworks?

  - by Pat

  (Skip to the bold if you want to get straight to my question :) ) I've been dabbling in the different technologies available out there to use. I tried Unity and component based design, managing to get a little guy up and running around a map with basic pathfinding. I really loved how easy it was to program using components, but I wanted a bit more control and something more 2D friendly, so I went with LibGDX. I looked around and found 2 good frameworks for Java, which are Artemis and Apollo. I didn't like Artemis much, so I went with Apollo, which I loved. I managed to integrate it with Box2D and get a little guy running around bouncing balls. Great! But since I want to try out most of the options, there is still C++/SFML that I haven't tried yet. Coming from a Java/C# background, I've always wanted to get my hands dirty with C++. But then, after some looking around, I noticed there aren't any Component-Based frameworks for me to use. There's a somewhat done porting of Artemis, but, aside from not being completely finished, I didn't quite like Artemis even in Java. I found Apollo's approach much more.. logical. So, my question is, are there any good Component/Entity frameworks for C++ that I can use that are similar to Artemis, or preferably, Apollo?

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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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