glsl

cesium中内置了一些常量、变量和函数，在vs和fs中可直接使用。 内置uniform 内置uniform主要置于AutomaticUniforms类里面，该类私有未开放文档。 czm_backgroundColor An automatic GLSL uniform representing the current scene background color. Example: // GLSL declaration uniform vec4 czm_backgroundColor; // Example: If the given color's RGB matches the background color, invert it. vec4 adjustColorForContrast(vec4 color) { if (czm_backgroundColor.rgb == color.rgb) { color.rgb = vec3(1.0) - color.rgb; } return color; } czm_brdfLut An automatic GLSL uniform containing the BRDF look up texture used for image-based lighting computations. Example: // GLSL

I'm working on a small graphics engine using OpenGL and I'm having some issues with my translation matrix. I'm using OpenGL 3.3, GLSL and C++. The situation is this: I have defined a small cube which I want to render on screen. The cube uses it's own coordinate system, so I created a model matrix to be able to transform the cube. To make it myself a bit easier I started out with just a translation matrix as the cube's model matrix and after a bit of coding I've managed to make everything work and the cube appears on the screen. Nothing all to special, but there is one thing about my

I'm currently working on a couple of shaders for an iPad game and it seems as if Apple's GLSL compiler isn't doing any optimizations (or very few). I can move a single line in a shader and drop my FPS from 30 to 24 but I really have no idea why this is happening. Does anyone have any references for the following: what PowerVR instructions are generated from GLSL instructions? what are the timings of the PowerVR instructions? what sort of parallel processing units are in the PowerVR535 and how can they be exploited? Thanks, Tristan http://www.imgtec.net/factsheets/SDK/POWERVR%20SGX.OpenGL%20ES

I have read some tutorials about GLSL. In certain position attribute is a vec4 in some vec3. I know that the matrix operations need a vec4, but is it worth to send an additional element? Isn't it better to send vec3 and later cast in the shader vec4(position, 1.0)? Less data in memory - it will be faster? Or we should pack an extra element to avoid casting? Any tips what should be better? layout(location = 0) in vec4 position; MVP*position; or layout(location = 0) in vec3 position; MVP*vec4(position,1.0); For vertex attributes, this will not matter. The 4th component is automatically expanded

When doing multitexturing in GLSL, is there anyway to have an indexable array of samplers where each texture is a different size? This syntax isn't valid: uniform sampler2D texArray[5]; Right now it seems like the only option is to individually create the samplers: uniform sampler2D tex1; uniform sampler2D tex2; uniform sampler2D tex3; uniform sampler2D tex4; uniform sampler2D tex5; But then I can't iterate through them, which is a real pain in the ass. Is there a solution? This syntax isn't valid: Says who? Arrays of samplers most certainly are valid (depending on the version). How you use

Should I prefer to calculate matrices on the CPU or GPU? Let's say I have the following matrices P * V * M , should I calculate them on the CPU so that I can send the final matrix to the GPU (GLSL) or should I send those three matrices separately to the GPU so that GLSL can calculate the final matrix? I mean in this case GLSL would have to calculate the MVP matrix for every vertex, so it is probably faster to precompute it on the CPU. But let's say that GLSL only has to calculate he MVP matrix once, would the GPU calculate the final matrix faster than the CPU? General rule: If you can pass it

I've been attempting to write a two-pass GPU implementation of the Marching Cubes algorithm, similar to the one detailed in the first chapter of GPU Gems 3, using OpenGL and GLSL. However, the call to glDrawArrays in my first pass consistently fails with a GL_INVALID_OPERATION . I've looked up all the documentation I can find, and found these conditions under which glDrawArrays can throw that error: GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to an enabled array or to the GL_DRAW_INDIRECT_BUFFER binding and the buffer object's data store is currently mapped. GL

I am using WebGL to resize images clientside very quickly within an app I am working on. I have written a GLSL shader that performs simple bilinear filtering on the images that I am downsizing. It works fine for the most part but there are many occasions where the resize is huge e.g. from a 2048x2048 image down to 110x110 in order to generate a thumbnail. In these instances the quality is poor and far too blurry. My current GLSL shader is as follows: uniform float textureSizeWidth;\ uniform float textureSizeHeight;\ uniform float texelSizeX;\ uniform float texelSizeY;\ varying mediump vec2