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  • How can I downsample a texture using FBOs?

    - by snape
    I am rendering a scene to FBO as my render target whose size is 8 times the size of the orignal screen in OpenGL. Now i wan to downsample the texture generated by FBO to the size of the screen so as to achieve spatial anti aliasing. How do i achieve the down sampling ? Please provide implementation details. Note : If there is a better way of doing anti aliasing in FBOs please mention that too. I am trying to remove the aliasing in the image attached below.

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  • Ray Tracing concers: Efficient Data Structure and Photon Mapping

    - by Grieverheart
    I'm trying to build a simple ray tracer for specific target scenes. An example of such scene can be seen below. I'm concerned as to what accelerating data structure would be most efficient in this case since all objects are touching but on the other hand, the scene is uniform. The objects in my ray tracer are stored as a collection of triangles, thus I also have access to individual triangles. Also, when trying to find the bounding box of the scene, how should infinite planes be handled? Should one instead use the viewing frustum to calculate the bounding box? A few other questions I have are about photon mapping. I've read the original paper by Jensen and many more material. In the compact data structure for the photon they introduce, they store photon power as 4 chars, which from my understanding is 3 chars for color and 1 for flux. But I don't understand how 1 char is enough to store a flux of the order of 1/n, where n is the number of photons (I'm also a bit confused about flux vs power). The other question about photon mapping is, if it would be more efficient in my case to store photons per object (or even per Object's triangle) instead of using a balanced kd-tree. Also, same question about bounding box of the scene but for photon mapping. How should one find a bounding box from the pov of the light when infinite planes are involved?

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  • Correct use of VAO's in OpenGL ES2 for iOS?

    - by sak
    I'm migrating to OpenGL ES2 for one of my iOS projects, and I'm having trouble to get any geometry to render successfully. Here's where I'm setting up the VAO rendering: void bindVAO(int vertexCount, struct Vertex* vertexData, GLushort* indexData, GLuint* vaoId, GLuint* indexId){ //generate the VAO & bind glGenVertexArraysOES(1, vaoId); glBindVertexArrayOES(*vaoId); GLuint positionBufferId; //generate the VBO & bind glGenBuffers(1, &positionBufferId); glBindBuffer(GL_ARRAY_BUFFER, positionBufferId); //populate the buffer data glBufferData(GL_ARRAY_BUFFER, vertexCount, vertexData, GL_STATIC_DRAW); //size of verte position GLsizei posTypeSize = sizeof(kPositionVertexType); glVertexAttribPointer(kVertexPositionAttributeLocation, kVertexSize, kPositionVertexTypeEnum, GL_FALSE, sizeof(struct Vertex), (void*)offsetof(struct Vertex, position)); glEnableVertexAttribArray(kVertexPositionAttributeLocation); //create & bind index information glGenBuffers(1, indexId); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *indexId); glBufferData(GL_ELEMENT_ARRAY_BUFFER, vertexCount, indexData, GL_STATIC_DRAW); //restore default state glBindVertexArrayOES(0); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0); glBindBuffer(GL_ARRAY_BUFFER, 0); } And here's the rendering step: //bind the frame buffer for drawing glBindFramebuffer(GL_FRAMEBUFFER, outputFrameBuffer); glClear(GL_COLOR_BUFFER_BIT); //use the shader program glUseProgram(program); glClearColor(0.4, 0.5, 0.6, 0.5); float aspect = fabsf(320.0 / 480.0); GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 0.1f, 100.0f); GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -1.0f); GLKMatrix4 mvpMatrix = GLKMatrix4Multiply(projectionMatrix, modelViewMatrix); //glUniformMatrix4fv(projectionMatrixUniformLocation, 1, GL_FALSE, projectionMatrix.m); glUniformMatrix4fv(modelViewMatrixUniformLocation, 1, GL_FALSE, mvpMatrix.m); glBindVertexArrayOES(vaoId); glDrawElements(GL_TRIANGLE_FAN, kVertexCount, GL_FLOAT, &indexId); //bind the color buffer glBindRenderbuffer(GL_RENDERBUFFER, colorRenderBuffer); [context presentRenderbuffer:GL_RENDERBUFFER]; The screen is rendering the color passed to glClearColor correctly, but not the shape passed into bindVAO. Is my VAO being built correctly? Thanks!

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  • Isometric algorithm producing tiles in wrong draw order

    - by David
    I've been toying with isometric and I just cant get the tiles to be in the right order. I'm probably missing something obvious and I just can't see it. Even at the risk of looking stupid, here's my code: for (int i = 0; i < Tile.MapSize; i++) { for (int j = 0; j < Tile.MapSize; j++) { spriteBatch.Draw( Tile.TileSetTexture, new Rectangle( (-j * Tile.TileWidth / 2) + (i * Tile.TileWidth / 2), (i * (Tile.TileHeight - 9) / 2) - (-j * (Tile.TileHeight - 9) / 2), Tile.TileWidth, Tile.TileHeight), Tile.GetSourceRectangle(tileID), Color.White, 0.0f, new Vector2(-350, -60), SpriteEffects.None, 1.0f); } } And here's what I end up with: messed up map Yep, bit of an issue. If anyone could help, I'd appreciate it.

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  • OpenGL position from depth is wrong

    - by CoffeeandCode
    My engine is currently implemented using a deferred rendering technique, and today I decided to change it up a bit. First I was storing 5 textures as so: DEPTH24_STENCIL8 - Depth and stencil RGBA32F - Position RGBA10_A2 - Normals RGBA8 x 2 - Specular & Diffuse I decided to minimize it and reconstruct positions from the depth buffer. Trying to figure out what is wrong with my method currently has not been fun :/ Currently I get this: which changes whenever I move the camera... weird Vertex shader really simple #version 150 layout(location = 0) in vec3 position; layout(location = 1) in vec2 uv; out vec2 uv_f; void main(){ uv_f = uv; gl_Position = vec4(position, 1.0); } Fragment shader Where the fun (and not so fun) stuff happens #version 150 uniform sampler2D depth_tex; uniform sampler2D normal_tex; uniform sampler2D diffuse_tex; uniform sampler2D specular_tex; uniform mat4 inv_proj_mat; uniform vec2 nearz_farz; in vec2 uv_f; ... other uniforms and such ... layout(location = 3) out vec4 PostProcess; vec3 reconstruct_pos(){ float z = texture(depth_tex, uv_f).x; vec4 sPos = vec4(uv_f * 2.0 - 1.0, z, 1.0); sPos = inv_proj_mat * sPos; return (sPos.xyz / sPos.w); } void main(){ vec3 pos = reconstruct_pos(); vec3 normal = texture(normal_tex, uv_f).rgb; vec3 diffuse = texture(diffuse_tex, uv_f).rgb; vec4 specular = texture(specular_tex, uv_f); ... do lighting ... PostProcess = vec4(pos, 1.0); // Just for testing } Rendering code probably nothing wrong here, seeing as though it always worked before this->gbuffer->bind(); gl::Clear(gl::COLOR_BUFFER_BIT | gl::DEPTH_BUFFER_BIT); gl::Enable(gl::DEPTH_TEST); gl::Enable(gl::CULL_FACE); ... bind geometry shader and draw models and shiz ... gl::Disable(gl::DEPTH_TEST); gl::Disable(gl::CULL_FACE); gl::Enable(gl::BLEND); ... bind textures and lighting shaders shown above then draw each light ... gl::BindFramebuffer(gl::FRAMEBUFFER, 0); gl::Clear(gl::COLOR_BUFFER_BIT | gl::DEPTH_BUFFER_BIT); gl::Disable(gl::BLEND); ... bind screen shaders and draw quad with PostProcess texture ... Rinse_and_repeat(); // not actually a function ;) Why are my positions being output like they are?

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  • Sharing VBO with multiple objects and fixed size buffer data

    - by Mark Ingram
    I'm just messing around with OpenGL and getting some basic structures in place and my first attempt resulted in each SceneObject class (just contains vertex information right now) having it's own VBO inside it, however I've read that it might be better to share VBOs across multiple objects. Also, I read that you should avoid resizing a VBO (repeated calls to glBufferData with different size parameters), and instead choose a fixed size for a VBO, and just try a range from the buffer. I don't think changing the size of the buffer data would happen too often, but surely it would be better to only allocate the data you need? Choosing an arbitrary value seems risky. I'm looking for some advice on working with individual objects in a scene and their associated buffer data.

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  • 2d Ice movement

    - by Jeremy Clarkson
    I am building an top-down 2d RPG like zelda. I have been trying to implement ice sliding. I have a tile with the slide property. I thought it would be easy to get working. I figured that I would read the slide property, and move the character forward until the slide property no longer exists. So I tried a loop but all it did was stop at the first tile in an infinite loop. I then took the loop out and tried taking direct control of the character to move him along the slide path but I couldn't get it to move. Is there an easy way to do an ice sliding tile based movement in libgdx. I looked for a tutorial but none exist.

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  • Using Appendbuffers in unity for terrain generation

    - by Wardy
    Like many others I figured I would try and make the most of the monster processing power of the GPU but I'm having trouble getting the basics in place. CPU code: using UnityEngine; using System.Collections; public class Test : MonoBehaviour { public ComputeShader Generator; public MeshTopology Topology; void OnEnable() { var computedMeshPoints = ComputeMesh(); CreateMeshFrom(computedMeshPoints); } private Vector3[] ComputeMesh() { var size = (32*32) * 4; // 4 points added for each x,z pos var buffer = new ComputeBuffer(size, 12, ComputeBufferType.Append); Generator.SetBuffer(0, "vertexBuffer", buffer); Generator.Dispatch(0, 1, 1, 1); var results = new Vector3[size]; buffer.GetData(results); buffer.Dispose(); return results; } private void CreateMeshFrom(Vector3[] generatedPoints) { var filter = GetComponent<MeshFilter>(); var renderer = GetComponent<MeshRenderer>(); if (generatedPoints.Length > 0) { var mesh = new Mesh { vertices = generatedPoints }; var colors = new Color[generatedPoints.Length]; var indices = new int[generatedPoints.Length]; //TODO: build this different based on topology of the mesh being generated for (int i = 0; i < indices.Length; i++) { indices[i] = i; colors[i] = Color.blue; } mesh.SetIndices(indices, Topology, 0); mesh.colors = colors; mesh.RecalculateNormals(); mesh.Optimize(); mesh.RecalculateBounds(); filter.sharedMesh = mesh; } else { filter.sharedMesh = null; } } } GPU code: #pragma kernel Generate AppendStructuredBuffer<float3> vertexBuffer : register(u0); void genVertsAt(uint2 xzPos) { //TODO: put some height generation code here. // could even run marching cubes / dual contouring code. float3 corner1 = float3( xzPos[0], 0, xzPos[1] ); float3 corner2 = float3( xzPos[0] + 1, 0, xzPos[1] ); float3 corner3 = float3( xzPos[0], 0, xzPos[1] + 1); float3 corner4 = float3( xzPos[0] + 1, 0, xzPos[1] + 1 ); vertexBuffer.Append(corner1); vertexBuffer.Append(corner2); vertexBuffer.Append(corner3); vertexBuffer.Append(corner4); } [numthreads(32, 1, 32)] void Generate (uint3 threadId : SV_GroupThreadID, uint3 groupId : SV_GroupID) { uint2 currentXZ = unint2( groupId.x * 32 + threadId.x, groupId.z * 32 + threadId.z); genVertsAt(currentXZ); } Can anyone explain why when I call "buffer.GetData(results);" on the CPU after the compute dispatch call my buffer is full of Vector3(0,0,0), I'm not expecting any y values yet but I would expect a bunch of thread indexes in the x,z values for the Vector3 array. I'm not getting any errors in any of this code which suggests it's correct syntax-wise but maybe the issue is a logical bug. Also: Yes, I know I'm generating 4,000 Vector3's and then basically round tripping them. However, the purpose of this code is purely to learn how round tripping works between CPU and GPU in Unity.

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  • Efficiently representing a dynamic transform hierarchy

    - by Mattia
    I'm looking for a way to represent a dynamic transform hierarchy (i.e. one where nodes can be inserted and removed arbitrarily) that's a bit more efficient than using a standard tree of pointers . I saw the answers to this question ( Efficient structure for representing a transform hierarchy. ), but as far as I can determine the tree-as-array approach only works for static hierarchies or dynamic ones where nodes have a fixed number of children (both deal-breakers for me). I'm probably wrong about that but could anyone point out how? If I'm not wrong are there other alternatives that work for dynamic hierarchies?

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  • Dynamic libraries are not allowed on iOS but what about this?

    - by tapirath
    I'm currently using LuaJIT and its FFI interface to call C functions from LUA scripts. What FFI does is to look at dynamic libraries' exported symbols and let the developer use it directly form LUA. Kind of like Python ctypes. Obviously using dynamic libraries is not permitted in iOS for security reasons. So in order to come up with a solution I found the following snippet. /* (c) 2012 +++ Filip Stoklas, aka FipS, http://www.4FipS.com +++ THIS CODE IS FREE - LICENSED UNDER THE MIT LICENSE ARTICLE URL: http://forums.4fips.com/viewtopic.php?f=3&t=589 */ extern "C" { #include <lua.h> #include <lualib.h> #include <lauxlib.h> } // extern "C" #include <cassert> // Please note that despite the fact that we build this code as a regular // executable (exe), we still use __declspec(dllexport) to export // symbols. Without doing that FFI wouldn't be able to locate them! extern "C" __declspec(dllexport) void __cdecl hello_from_lua(const char *msg) { printf("A message from LUA: %s\n", msg); } const char *lua_code = "local ffi = require('ffi') \n" "ffi.cdef[[ \n" "const char * hello_from_lua(const char *); \n" // matches the C prototype "]] \n" "ffi.C.hello_from_lua('Hello from LUA!') \n" // do actual C call ; int main() { lua_State *lua = luaL_newstate(); assert(lua); luaL_openlibs(lua); const int status = luaL_dostring(lua, lua_code); if(status) printf("Couldn't execute LUA code: %s\n", lua_tostring(lua, -1)); lua_close(lua); return 0; } // output: // A message from LUA: Hello from LUA! Basically, instead of using a dynamic library, the symbols are exported directly inside the executable file. The question is: is this permitted by Apple? Thanks.

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  • Implementing top view physics using box2D

    - by humbleBee
    How can top view physics games be done in box2D? One idea I have is to set the linear velocity of an object manually or to alter the linear and angular damping as my object moves over different surfaces. For example if my object is over a wet surface it'll have less linear damping and if it is over rough surface it'll have more damping. And to see if my object has fallen over an edge I'll try to use an AABB and check if its still inside or manually see if object.x > boundary.x etc. Is there any better way?

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  • Masking OpenGL texture by a pattern

    - by user1304844
    Tiled terrain. User wants to build a structure. He presses build and for each tile there is an "allow" or "disallow" tile sprite added to the scene. FPS drops right away, since there are 600+ tiles added to the screen. Since map equals screen, there is no scrolling. I came to an idea to make an allow grid covering the whole map and mask the disallow fields. Approach 1: Create allow and disallow grid textures. Draw a polygon on screen. Pass both textures to the fragment shader. Determine the position inside the polygon and use color from allowTexture if the fragment belongs to the allow field, disallow otherwise Problem: How do I know if I'm on the field that isn't allowed if I cannot pass the matrix representing the map (enum FieldStatus[][] (Allow / Disallow)) to the shader? Therefore, inside the shader I don't know which fragments should be masked. Approach 2: Create allow texture. Create an empty texture buffer same size as the allow texture Memset the pixels of the empty texture to desired color for each pixel that doesn't allow building. Draw a polygon on screen. Pass both textures to the fragment shader. Use texture2 color if alpha 0, texture1 color otherwise. Problem: I'm not sure what is the right way to manipulate pixels on a texture. Do I just make a buffer with width*height*4 size and memcpy the color[] to desired coordinates or is there anything else to it? Would I have to call glTexImage2D after every change to the texture? Another problem with this approach is that it takes a lot more work to get a prettier effect since I'm manipulating the color pixels instead of just masking two textures. varying vec2 TexCoordOut; uniform sampler2D Texture1; uniform sampler2D Texture2; void main(void){ vec4 allowColor = texture2D(Texture1, TexCoordOut); vec4 disallowColor = texture2D(Texture2, TexCoordOut); if(disallowColor.a > 0){ gl_FragColor= disallowColor; }else{ gl_FragColor= allowColor; }} I'm working with OpenGL on Windows. Any other suggestion is welcome.

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  • Hardware instancing for voxel engine

    - by Menno Gouw
    i just did the tutorial on Hardware Instancing from this source: http://www.float4x4.net/index.php/2011/07/hardware-instancing-for-pc-in-xna-4-with-textures/. Somewhere between 900.000 and 1.000.000 draw calls for the cube i get this error "XNA Framework HiDef profile supports a maximum VertexBuffer size of 67108863." while still running smoothly on 900k. That is slightly less then 100x100x100 which are a exactly a million. Now i have seen voxel engines with very "tiny" voxels, you easily get to 1.000.000 cubes in view with rough terrain and a decent far plane. Obviously i can optimize a lot in the geometry buffer method, like rendering only visible faces of a cube or using larger faces covering multiple cubes if the area is flat. But is a vertex buffer of roughly 67mb the max i can work with or can i create multiple?

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  • WIn API Basic Paint program

    - by Tom Burman
    Just trying to learn a bit of Win API. Im trying to make a basic drawing app, a bit like MS Paint. For the time being im trying to get one function to work which is, when you left click and drag the mouse around the screen a line is drawn behind the mouse. Heres what i have so far, but for some reason: 1) the line starts drawing straight away rather then waiting for the left click 2) the line isn't solid its very dotty. case WM_MOUSEMOVE: { if(MK_LBUTTON){ hdc = GetDC(hwnd); hPen = CreatePen(PS_SOLID,5,RGB(0, 0, 255)); SelectObject(hdc, hPen); int x = LOWORD(lParam); int y = HIWORD(lParam); MoveToEx(hdc,x,y,NULL); LineTo(hdc, LOWORD(lParam), HIWORD(lParam)); ReleaseDC(hwnd,hdc); } else break; } } Thanks for any help!

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  • Problem with DirectX scene-graph

    - by Alex
    I'm trying to implement a basic scene graph in DirectX using C++. I am using a left child-right sibling binary tree to do this. I'm having trouble updating each node's world transformation relative to its parent (and its parent's parent etc.). I'm struggling to get it to work recursively, though I can get it to work like this: for(int i = 0; i < NUM_OBJECTS; i++) { // Initialize to identity matrix. D3DXMatrixIdentity(&mObject[i].toWorldXForm); int k = i; while( k != -1 ) { mObject[i].toWorldXForm *= mObject[k].toParentXForm; k = mObject[k].parent; } } toWorldXForm is the object's world transform and toParentXForm is the object's transform relative to the parent. I want to do this using a method within my object class (the code above is in my main class). This is what I've tried but it doesn't work (only works with nodes 1 generation away from the root) if (this->sibling != NULL) this->sibling->update(toParentXForm); D3DXMatrixIdentity(&toWorldXForm); this->toWorldXForm *= this->toParentXForm; this->toWorldXForm *= toParentXForm; toParentXForm *= this->toParentXForm; if (this->child != NULL) this->child->update(toParentXForm); Sorry if I've not been clear, please tell me if there's anything else you need to know. I've no doubt it's merely a silly mistake on my part, hopefully an outside view will be able to spot the problem.

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  • OpenGL ES Loading

    - by kuroutadori
    I want to know what is the norm of loading rendering code. Take a button. When the application is loaded, a texture is loaded which has the image of the button on it. When the button is tapped, it then adds a loader into a queue, which is loaded on render thread. It then loads up an array buffer with vertexes and tex coords when render is called. It then adds to a render tree. Then it renders. the render function looks like this void render() { update(); mBaseRenderer->render(); } update() is when the queue is checked to see if anything needs loading. mBaseRenderer->render() is the render tree. What I am asking then is, should I even have the update() there at all and instead have everything preloaded before it renders? If I can have it loaded when need, for instance when there is tap, then how can it be done (My current code causes an dequeueing buffer error (Unknown error: -75) which I assume is to do with OpenGL ES and the context)?

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  • OpenGLES GLSL Shader attributes always bound to 0

    - by codemonkey
    So I have a very simple vertex shader as follows #version 120 attribute vec3 position; attribute vec3 inColor; uniform mat4 mvp; varying vec3 fragColor; void main(void){ fragColor = inColor; gl_Position = mvp * vec4(position, 1.0); } Which I load, as well as the fragment shader: #version 120 varying vec3 fragColor; void main(void) { gl_FragColor = vec4(fragColor,1.0); } Which I then load, compile, and link to my shader program. I check for link status using glGetProgramiv(shaderProgram, GL_LINK_STATUS, &shaderSuccess); which returns GL_TRUE so I think its ok. However, when I query the active attributes and uniforms using #ifdef DEBUG int totalAttributes = -1; glGetProgramiv(shaderProgram, GL_ACTIVE_ATTRIBUTES, &totalAttributes); for(int i=0; i<totalAttributes; ++i) { int name_len=-1, num=-1; GLenum type = GL_ZERO; char name[100]; glGetActiveAttrib(shaderProgram, GLuint(i), sizeof(name)-1, &name_len, &num, &type, name ); name[name_len] = 0; GLuint location = glGetAttribLocation(shaderProgram, name); fprintf(stderr, "Attribute %s is bound at %d\n", name, location); } int totalUniforms = -1; glGetProgramiv(shaderProgram, GL_ACTIVE_UNIFORMS, &totalUniforms); for(int i=0; i<totalUniforms; ++i) { int name_len=-1, num=-1; GLenum type = GL_ZERO; char name[100]; glGetActiveUniform(shaderProgram, GLuint(i), sizeof(name)-1, &name_len, &num, &type, name ); name[name_len] = 0; GLuint location = glGetUniformLocation(shaderProgram, name); fprintf(stderr, "Uniform %s is bound at %d\n", name, location); } #endif I get: Attribute inColor is bound at 0 Attribute position is bound at 1 Uniform mvp is bound at 0 Which leads to failure when trying to use the shader to render the objects. I have tried switching the order of declaration of position & inColor, but still, only position is bound with the other two giving 0 Can someone please explain why this is happening? Thanks

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  • Safe zone implementation in Asteroids

    - by Moaz
    I would like to implement a safe zone for asteroids so that when the ship gets destroyed, it shouldn't be there unless it is safe from other asteroids. I tried to check the distance between each asteroid and the ship, and if it is above threshold, it sets a flag to the ship that's a safe zone, but sometimes it work and sometimes it doesn't. What am I doing wrong? Here's my code: for (list<Asteroid>::iterator itr_astroid = asteroids.begin(); itr_astroid!=asteroids.end(); ) { if(currentShip.m_state == Ship::Ship_Dead) { float distance = itr_astroid->getCenter().distance(Vec2f(getWindowWidth()/2,getWindowHeight()/2)); if( distance>200) { currentShip.m_saveField = true; break; } else { currentShip.m_saveField = false; itr_astroid++; } } else { itr_astroid++; } } At ship's death: if(m_state == Ship_Dead && m_saveField==true) { --m_lifeSpan; } if(m_lifeSpan<=0 && m_saveField == true) { m_state = Ship_Alive; m_Vel = Vec2f(0,0); m_Pos.x = app::getWindowWidth()/2; m_Pos.y = app::getWindowHeight()/2; m_lifeSpan = 100; }

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  • Saving a list of points into a text file

    - by dylanisawesome1
    I recently posted a question about this, but was not really sure where to go. I've gotten some progress, and have generated some simple noise here: http://pastie.org/5408655 That works well enough for me, but I would really like to be able to save the points into an ascii text file. currently it's formatted so that something like this: http://pastie.org/5409311 would create a square. I need to save in this format with the points(and lines connecting them) generated in the method above. Essentially, I need to write the array of points created in the first example to a text file formatted like the second example.

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  • Getting the number of fragments which passed the depth test

    - by Etan
    In "modern" environments, the "NV Occlusion Query" extension provides a method to get the number of fragments which passed the depth test. However, on the iPad / iPhone using OpenGL ES, the extension is not available. What is the most performant approach to implement a similar behaviour in the fragment shader? Some of my ideas: Render the object completely in white, then count all the colors together using a two-pass shader where first a vertical line is rendered and for each fragment the shader computes the sum over the whole row. Then, a single vertex is rendered whose fragment sums all the partial sums of the first pass. Doesn't seem to be very efficient. Render the object completely in white over a black background. Downsample recursively, abusing the hardware linear interpolation between textures until being at a reasonably small resolution. This leads to fragments which have a greyscale level depending on the number of white pixels where in their corresponding region. Is this even accurate enough? Use mipmaps and simply read the pixel on the 1x1 level. Again the question of accuracy and if it is even possible using non-power-of-two textures. The problem wit these approaches is, that the pipeline gets stalled which results in major performance issues. Therefore, I'm looking for a more performant way to accomplish my goal. Using the EXT_OCCLUSION_QUERY_BOOLEAN extension Apple introduced EXT_OCCLUSION_QUERY_BOOLEAN in iOS 5.0 for iPad 2. "4.1.6 Occlusion Queries Occlusion queries use query objects to track the number of fragments or samples that pass the depth test. An occlusion query can be started and finished by calling BeginQueryEXT and EndQueryEXT, respectively, with a target of ANY_SAMPLES_PASSED_EXT or ANY_SAMPLES_PASSED_CONSERVATIVE_EXT. When an occlusion query is started with the target ANY_SAMPLES_PASSED_EXT, the samples-boolean state maintained by the GL is set to FALSE. While that occlusion query is active, the samples-boolean state is set to TRUE if any fragment or sample passes the depth test. When the occlusion query finishes, the samples-boolean state of FALSE or TRUE is written to the corresponding query object as the query result value, and the query result for that object is marked as available. If the target of the query is ANY_SAMPLES_PASSED_CONSERVATIVE_EXT, an implementation may choose to use a less precise version of the test which can additionally set the samples-boolean state to TRUE in some other implementation dependent cases." The first sentence hints on a behavior which is exactly what I'm looking for: getting the number of pixels which passed the depth test in an asynchronous manner without much performance loss. However, the rest of the document describes only how to get boolean results. Is it possible to exploit this extension to get the pixel count? Does the hardware support it so that there may be hidden API to get access to the pixel count? Other extensions which could be exploitable would be debugging features like the number of times the fragment shader was invoked (PSInvocations in DirectX - not sure if something simila is available in OpenGL ES). However, this would also result in a pipeline stall.

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  • how to label a cuboid using open gl?

    - by usha
    hi this is how my 3dcuboid looks ,i have attached complete code , i want to label this cuboid using different name across sides how is it possible using opengl in android...plz help me out public class MyGLRenderer implements Renderer { Context context; Cuboid rect; private float mCubeRotation; // private static float angleCube = 0; // Rotational angle in degree for cube (NEW) // private static float speedCube = -1.5f; // Rotational speed for cube (NEW) public MyGLRenderer(Context context) { rect = new Cuboid(); this.context = context; } public void onDrawFrame(GL10 gl) { // TODO Auto-generated method stub gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); gl.glLoadIdentity(); // Reset the model-view matrix gl.glTranslatef(0.2f, 0.0f, -8.0f); // Translate right and into the screen gl.glScalef(0.8f, 0.8f, 0.8f); // Scale down (NEW) gl.glRotatef(mCubeRotation, 1.0f, 1.0f, 1.0f); // gl.glRotatef(angleCube, 1.0f, 1.0f, 1.0f); // rotate about the axis (1,1,1) (NEW) rect.draw(gl); mCubeRotation -= 0.15f; //angleCube += speedCube; } public void onSurfaceChanged(GL10 gl, int width, int height) { // TODO Auto-generated method stub if (height == 0) height = 1; // To prevent divide by zero float aspect = (float)width / height; // Set the viewport (display area) to cover the entire window gl.glViewport(0, 0, width, height); // Setup perspective projection, with aspect ratio matches viewport gl.glMatrixMode(GL10.GL_PROJECTION); // Select projection matrix gl.glLoadIdentity(); // Reset projection matrix // Use perspective projection GLU.gluPerspective(gl, 45, aspect, 0.1f, 100.f); gl.glMatrixMode(GL10.GL_MODELVIEW); // Select model-view matrix gl.glLoadIdentity(); // Reset } public void onSurfaceCreated(GL10 gl, EGLConfig config) { // TODO Auto-generated method stub gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Set color's clear-value to black gl.glClearDepthf(1.0f); // Set depth's clear-value to farthest gl.glEnable(GL10.GL_DEPTH_TEST); // Enables depth-buffer for hidden surface removal gl.glDepthFunc(GL10.GL_LEQUAL); // The type of depth testing to do gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); // nice perspective view gl.glShadeModel(GL10.GL_SMOOTH); // Enable smooth shading of color gl.glDisable(GL10.GL_DITHER); // Disable dithering for better performance }} public class Cuboid{ private FloatBuffer mVertexBuffer; private FloatBuffer mColorBuffer; private ByteBuffer mIndexBuffer; private float vertices[] = { //width,height,depth -2.5f, -1.0f, -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, 1.0f, -1.0f, -2.5f, 1.0f, -1.0f, -2.5f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f, -2.5f, 1.0f, 1.0f }; private float colors[] = { // R,G,B,A COLOR 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.5f, 0.0f, 1.0f, 1.0f, 0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f }; private byte indices[] = { // VERTEX 0,1,2,3,4,5,6,7 REPRESENTATION FOR FACES 0, 4, 5, 0, 5, 1, 1, 5, 6, 1, 6, 2, 2, 6, 7, 2, 7, 3, 3, 7, 4, 3, 4, 0, 4, 7, 6, 4, 6, 5, 3, 0, 1, 3, 1, 2 }; public Cuboid() { ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4); byteBuf.order(ByteOrder.nativeOrder()); mVertexBuffer = byteBuf.asFloatBuffer(); mVertexBuffer.put(vertices); mVertexBuffer.position(0); byteBuf = ByteBuffer.allocateDirect(colors.length * 4); byteBuf.order(ByteOrder.nativeOrder()); mColorBuffer = byteBuf.asFloatBuffer(); mColorBuffer.put(colors); mColorBuffer.position(0); mIndexBuffer = ByteBuffer.allocateDirect(indices.length); mIndexBuffer.put(indices); mIndexBuffer.position(0); } public void draw(GL10 gl) { gl.glFrontFace(GL10.GL_CW); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mVertexBuffer); gl.glColorPointer(4, GL10.GL_FLOAT, 0, mColorBuffer); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_COLOR_ARRAY); gl.glDrawElements(GL10.GL_TRIANGLES, 36, GL10.GL_UNSIGNED_BYTE, mIndexBuffer); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_COLOR_ARRAY); } } public class Draw3drect extends Activity { private GLSurfaceView glView; // Use GLSurfaceView // Call back when the activity is started, to initialize the view @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); glView = new GLSurfaceView(this); // Allocate a GLSurfaceView glView.setRenderer(new MyGLRenderer(this)); // Use a custom renderer this.setContentView(glView); // This activity sets to GLSurfaceView } // Call back when the activity is going into the background @Override protected void onPause() { super.onPause(); glView.onPause(); } // Call back after onPause() @Override protected void onResume() { super.onResume(); glView.onResume(); } }

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  • Mandelbrot set not displaying properly

    - by brainydexter
    I am trying to render mandelbrot set using glsl. I'm not sure why its not rendering the correct shape. Does the mandelbrot calculation require values to be within a range for the (x,y) [ or (real, imag) ] ? Here is a screenshot: I render a quad as follows: float w2 = 6; float h2 = 5; glBegin(GL_QUADS); glVertex3f(-w2, h2, 0.0); glVertex3f(-w2, -h2, 0.0); glVertex3f(w2, -h2, 0.0); glVertex3f(w2, h2, 0.0); glEnd(); My vertex shader: varying vec3 Position; void main(void) { Position = gl_Vertex.xyz; gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; } My fragment shader (where all the meat is): uniform float MAXITERATIONS; varying vec3 Position; void main (void) { float zoom = 1.0; float centerX = 0.0; float centerY = 0.0; float real = Position.x * zoom + centerX; float imag = Position.y * zoom + centerY; float r2 = 0.0; float iter; for(iter = 0.0; iter < MAXITERATIONS && r2 < 4.0; ++iter) { float tempreal = real; real = (tempreal * tempreal) + (imag * imag); imag = 2.0 * real * imag; r2 = (real * real) + (imag * imag); } vec3 color; if(r2 < 4.0) color = vec3(1.0); else color = vec3( iter / MAXITERATIONS ); gl_FragColor = vec4(color, 1.0); }

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  • Skip the first RenderTarget when writing to MRT with Opaque blending

    - by cubrman
    I am writing to three rendertargets and whant to know how to tell a GPU not to write to the first RT. When you write a shader you can simply output less data than you have RTs (like output a single float4 when writing to three RTs) and only the first RTs will be affected, but you cannot specify to output this data anywhere else but to COLOR0, then 1, etc. Is there a way to write to several RTs but skip the first target? If I output zeroes, the data in the target will become zeroes, but I need it to remain untuched in the first target and only change in the specified ones. The reason I need this is to prevent data loss when calling SetRendertarget() with DiscardContents RTs. I write to all the RTs at one point and I need to write to only the specified ones afterwards. It must be the first texture as I have a depth buffer linked to it (XNA 4.0). Thanks.

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  • Drawing a random x,y grid of objects within a prespective

    - by T Reddy
    I'm wrapping my head around OpenGL ES 2.0 and I think I'm trying to do something very simple, but I think the math may be eluding me. I created a simple, flat-ish cylinder in Blender that is 2 units in diameter. I want to create an arbitrary grid of these edge to edge (think of a checker board). I'm using a 3D perspective with GLKit: CGSize size = [[self view] bounds].size; _projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(45.0f), size.width/size.height, 0.1f, 100.0f); So, I managed to manually get all of these cylinders drawn on the screen just fine. However, I would like to understand how I can programmatically "fit" all of these cylinders on the screen at the same time given the camera location, screen size, cylinder diameter, and the number of rows/columns. So the net effect is that for small grids (i.e., 5x5) the objects are closer to the camera, but for large grids (i.e., 30x30) the objects are farther away. In either case, all of the cylinders are visible.

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  • Is it safe StringToHash() to use in Unity?

    - by Sebastian Krysmanski
    I'm currently browsing through the Unity tutorials and saw that they're recommending to use Animator.StringToHash("some string") to created unique ids for animation properties (see here). Since I'm a programmer, to me the word "hash" doesn't represents something unique. Like the Java documentation for hashValue() states: It is not required that if two objects are unequal [...], then calling the hashCode method on each of the two objects must produce distinct integer results. So, according to this (and my definition of "hash"), two strings may have the same hash value. (You can also argue that there are an infinite number of possible strings but only 2^32 possible int values.) So, is there a possibility that StringToHash() will give me an id that actually belongs to another property (than the one I requested the hash for)?

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