shader – Page 3 – Tarik Billa

Getting the true z value from the depth buffer

March 10, 2023 by Tarik

From http://web.archive.org/web/20130416194336/http://olivers.posterous.com/linear-depth-in-glsl-for-real // == Post-process frag shader =========================================== uniform sampler2D depthBuffTex; uniform float zNear; uniform float zFar; varying vec2 vTexCoord; void main(void) { float z_b = texture2D(depthBuffTex, vTexCoord).x; float z_n = 2.0 * z_b – 1.0; float z_e = 2.0 * zNear * zFar / (zFar + zNear – z_n * (zFar – zNear)); } … Read more

Creating a GLSL Arrays of Uniforms?

February 2, 2023 by Tarik

Yes this is possible. You declare uniform arrays similar to how you’d do it in C, e.g. uniform float v[10]; Then you can set their values using glUniform{1,2,3,4}{f,i}v GLfloat v[10] = {…}; glUniform1fv(glGetUniformLocation(program, “v”), 10, v);

Explicit vs Automatic attribute location binding for OpenGL shaders

January 27, 2023 by Tarik

I know one good reason to prefer explicit location definition. Consider that you hold your geometry data in Vertex Array Objects. For a given object, you create a VAO in such way that the indices correspond to, for example: index 0: positions, index 1: normals, index 2: texcoords Now consider that you want to draw … Read more

What are Vertex and Pixel shaders?

January 22, 2023 by Tarik

DirectX 10 and OpenGL 3 introduced the Geometry Shader as a third type. In rendering pipeline order – Vertex Shader – Takes a single point and can adjust it. Can be used to work out complex **vertex lighting calcs as a setup for the next stage and/or warp the points around (wobble, scale, etc). each … Read more

Do conditional statements slow down shaders?

January 1, 2023 by Tarik

What is it about shaders that even potentially makes if statements performance problems? It has to do with how shaders get executed and where GPUs get their massive computing performance from. Separate shader invocations are usually executed in parallel, executing the same instructions at the same time. They’re simply executing them on different sets of … Read more

What’s the origin of this GLSL rand() one-liner?

December 25, 2022 by Tarik

Very interesting question! I am trying to figure this out while typing the answer 🙂 First an easy way to play with it: http://www.wolframalpha.com/input/?i=plot%28+mod%28+sin%28x*12.9898+%2B+y*78.233%29+*+43758.5453%2C1%29x%3D0..2%2C+y%3D0..2%29 Then let’s think about what we are trying to do here: For two input coordinates x,y we return a “random number”. Now this is not a random number though. It’s the … Read more

What is the correct file extension for GLSL shaders? [closed]

November 19, 2022 by Tarik

There’s no official extension in the spec. OpenGL doesn’t handle loading shaders from files; you just pass in the shader code as a string, so there’s no specific file format. However, glslang, Khronos’ reference GLSL compiler/validator, uses the following extensions to determine what type of shader that the file is for: .vert – a vertex … Read more

What is state-of-the-art for text rendering in OpenGL as of version 4.1? [closed]

October 15, 2022 by Tarik

Rendering outlines, unless you render only a dozen characters total, remains a “no go” due to the number of vertices needed per character to approximate curvature. Though there have been approaches to evaluate bezier curves in the pixel shader instead, these suffer from not being easily antialiased, which is trivial using a distance-map-textured quad, and … Read more

Random / noise functions for GLSL

October 12, 2022 by Tarik

For very simple pseudorandom-looking stuff, I use this oneliner that I found on the internet somewhere: float rand(vec2 co){ return fract(sin(dot(co, vec2(12.9898, 78.233))) * 43758.5453); } You can also generate a noise texture using whatever PRNG you like, then upload this in the normal fashion and sample the values in your shader; I can dig … Read more