glsl

While writing a shader program today, I encountered a situation where I have to use % to find the remainder. GLSL gave me an error saying that it is not available in the current version. I've tried several problems. GLSL doesn't support recursive function and while loops, which is needed if I want to create a function that can give me the result of (a % b) . So, I'm currently stuck. Can someone help me with this? Edit . I was trying to emulate a CRT screen using some shader code from this website as reference code. I wanted to modify the color of the pixels at certain row and columns, so I

gl_FragCoord和gl_FragDepth分别是片元着色器的输入和输出变量。 gl_FragCoord是个vec4，四个分量分别对应x, y, z和1/w。其中，x和y是当前片元的窗口相对坐标，不过它们不是整数，小数部分恒为0.5。x - 0.5和y - 0.5分别位于[0, windowWidth - 1]和[0, windowHeight - 1]内。windowWidth和windowHeight都以像素为单位，亦即用glViewPort指定的宽高。w即为乘过了投影矩阵之后点坐标的w，用于perspective divide的那个值。gl_FragCoord.z / gl_FragCoord.w可以得到当前片元和camera之间的距离。参见Fog in GLSL page 4。 gl_FragCoord.z是固定管线计算出的当前片元的深度。它已经考虑了多边形偏移，并经过了投影变换。它位于[0.0, 1.0]之间。如果用gl_FragColor = vec4(vec3(gl_FragCoord.z), 1.0)将其可视化，多半会看到一片白。这是由于变换的非线性，大多数点的深度都非常接近于1。用gl_FragColor = vec4(vec3(pow(gl_FragColor.z, exp)), 1.0)并将exp取为合适的值，就能看到从黑到白的深度变化了

I'm on a Mac, using Swift, and using OpenGL 3.2. I'm also using XCode 6.1 Beta so I suppose that's the most likely explanation, because it doesn't seem to me like this makes sense. I can't find any evidence that this shouldn't be supported, but this fragment shader is resulting in the error Invalid call of undeclared identifier 'texture2D' during compilation: #version 150 uniform sampler2D usTexture; in vec2 vTextureCoord; out vec4 FragColor; void main() { vec4 color = texture2D(usTexture, vTextureCoord); FragColor = color; } Cripes. Finally found the answer right after I posted the question.

I'm trying to implement textured points (e.g. point sprites) in OpenGL ES 2.0 for a particle system. Problem I'm having is the points all render as solid black squares, rather than having the texture properly mapped. I have verified that gl_PointCoord is in fact returning x/y values from 0.0 to 1.0, which would map across the entire texture. The texture2D call always seems to return black though. My vertex shader : attribute vec4 aPosition; attribute float aAlpha; attribute float aSize; varying float vAlpha; uniform mat4 uMVPMatrix; void main() { gl_PointSize = aSize; vAlpha = aAlpha; gl

I want to get the current depth buffer to a texture, to access it in a shader. For various reasons I can't do a separate depth pass, but would need to copy the already-rendered depth. glReadPixels would involve the CPU and potentially kill performance, and as far as I know glBlitFramebuffer can't blit depth-to-color, only depth-to-depth. How to do this on the GPU? The modern way of doing this would be to use a FBO. Attach a color and depth texture to it, render, then disable the FBO and use the textures as inputs to a shader that will render to the default framebuffer. All the details you need

How can I enable an extension on a Three.js shader? My code so far: getting extension: var domElement = document.createElement( 'canvas' ); var gl = domElement.getContext('webgl') || domElement.getContext('experimental-webgl'); gl.getExtension('OES_standard_derivatives'); on my shader: fragmentShader: [ "#extension GL_OES_standard_derivatives : enable", "code..." ]... The console output: WARNING: 0:26: extension 'GL_OES_standard_derivatives' is not supported ERROR: 0:32: 'dFdx' : no matching overloaded function found ERROR: 0:32: '=' : cannot convert from 'const mediump float' to '2-component