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Questions tagged [glsl]

GLSL is the OpenGL shading language. Use this tag for questions which are specifically about shaders written in this language. For generic shader questions use [shader] instead.

21
votes
1answer
2k views

Why does my Perlin Noise look “blocky”?

I tried to implement Perlin Noise by myself using just the theory (following flafla2.github.io/2014/08/09/perlinnoise.html). Unfortunately I was unable to achieve the look of the "original" Perlin ...
6
votes
1answer
90 views

gamma transform in webGLSL: when already done or yet to be done?

Color spaces issues are such a pain, especially when you create color data at the middle of the chain, and a pile of libs and apps separate this to the display... Here I only worry about gamma ...
4
votes
1answer
623 views

Guidance with Sphere-Map calculation in GLSL

I'm trying to achieve the same effect in OpenGL/GLSL as what Blender does when you add a texture, set to "Reflection" This ultimately is a way to fake specularity, or "metallicness" if I get it right....
5
votes
2answers
350 views

Clearing but not drawing objects

I was trying to draw a plane and cubes in a framebuffer but nothing is drawing in that framebuffer besides clearing it with a color. Here's the code... ...
11
votes
1answer
2k views

Loop performance in a shader

I am wondering what's the best way to integrate a dynamic loop function in a shader? First, it seems that dynamic arrays are not possible. So, is it better to create a maximum size array and only ...
5
votes
1answer
198 views

Shadow map projection issue

I am using Unity but this question might not be proper to this engine. I have projected the shadow map onto this sphere but there are grazing shadows. Is it possible to avoid it or to correct it as I ...
5
votes
1answer
389 views

Methods for grid traversal in a glsl pixel shader?

I'm working on a shadertoy "snake" game, using the new multi pass rendering abilities to save game state between frames. I'm using raytracing to render the board (an AABB), and am planning on using ...
4
votes
1answer
365 views

Shader won't work

I have managed to implement a garoud shader with specular lighting efects in Processing 3.0 . Now I am trying with a fragment Phong shader but cannot make it work. I can´t find where is the error. It ...
7
votes
1answer
494 views

Flat shading for non-planar polygons

I'm trying to figure out how to properly implement flat shading for meshes containing non-planar polygons (using OpenGL/GLSL). The aim is to obtain something similar to the result Blender gives (all ...
4
votes
2answers
347 views

OpenGL vertex color

Why do I need to specify the same name for color input in fragment shader and output color from vertex shader? ...
4
votes
1answer
160 views

How to set the GLFW OpenGL target?

I'm programming on a Mac and I'm learning OpenGL in the library GLFW. My problem is that my Mac supports OpenGL up to version 4.1, but when I try to compile the shaders with ...
9
votes
1answer
616 views

WebGL Omnidirectional Shadow Mapping Issue

First of all, I want to say that I've read a lot of post about shadow mapping using depth maps and cubemaps and I understand how they work and also, I have working experience with them using OpenGL, ...
4
votes
0answers
170 views

Indexing gl_TessLevelOuter[] with gl_InvocationID on a tessellation control shader

I'm using hardware tessellation to render a terrain mesh with variable LOD. I have this snippet on my tessellation control shader: ...
4
votes
1answer
968 views

How to convert a thread ID into Screen Space Coord in an OpenGL Compute Shader?

I've written an implementation of the sphere tracing algorithm in OpenGL 4+. As an experiment/toy project, I'm re-implementing it using the OpenGL 4.3 compute shader, but I'm having trouble with the ...
5
votes
1answer
226 views

Can't get output from a GLSL code

I'm trying to learn GLSL, I'm following this tutorial. I've done everything according to the tutorials but I can't get any output from my code. As you see I'm checking for both compile errors and ...
7
votes
1answer
683 views

Shadow Mapping artefacts

I've been playing around with shadow mapping in OpenGL using depth textures. The depth texture is fine and I can map it onto the scene but I have some strange artefacts on the back of the object: My ...
7
votes
1answer
418 views

Shader uniform performance

I'd like to know if there's any performance impact based on how I struct my shader uniforms. For instance, is passing 4 floats worse than passing a single vec4?
11
votes
1answer
2k views

Do I need to rebind uniforms or attributes when changing shader programs?

Rendering the scene usually involves more than one shader program which, in my case, all use the same attributes and share at least some of the uniforms. To have them working properly, I currently ...
6
votes
2answers
235 views

What factors affect which shader language to learn?

I don't know any shader languages. I've heard of GLSL and HLSL, and I'm interested in learning one or both. Are there significant differences between them that would make one or other better in ...
9
votes
1answer
4k views

Why is accessing textures much slower when calculating the texture coordinate in the fragment shader?

When using textures in GLSL, it is best to calculate the final texture coordinates in the vertex shader and hand them over to the fragment shader using varyings. ...
9
votes
1answer
544 views

Trying to implement Microfacet BRDF but my result images are wrong

I am trying to implement microfacet BRDF model. I am reading Sebastien Lagarde's slides. I implemented formulas to my code but i think result image is wrong. Yellow is base color of material. ...
28
votes
4answers
8k views

Sharing code between multiple GLSL shaders

I often find myself copy-pasting code between several shaders. This includes both certain computations or data shared between all shaders in a single pipeline, and common computations which all of my ...
36
votes
6answers
17k views

How can I debug GLSL shaders?

When writing non-trivial shaders (just as when writing any other piece of non-trivial code), people make mistakes.[citation needed] However, I can't just debug it like any other code - you can't just ...
11
votes
1answer
871 views

When to disable perspective correct interpolation ( noperspective )

In GLSL, perspective correct interpolation of vertex attributes is the default setting - one can disable it for specific vertex attributes by using the noperspective qualifier. Other than in post-...