You don’t need precision specifiers on constants/literals since those get compile time evaluated to whatever they are being assigned to. In vertex shaders, the following precisions are declared by default: ( 4.5.3 Default Precision Qualifiers) precision highp float; precision highp int; precision lowp sampler2D; precision lowp samplerCube; And in fragment shaders you get: precision mediump … Read more
You don’t have to use <script> tags at all to load a shader program. Most tutorials and examples just use them as a container to store a string in the DOM of the webpage. The script type “x-shader/x-fragment” is meaningless for web browsers, so they don’t execute the script. They do, however, store the content … Read more
Each shader stage has its own frequency of invocations. I will use the OpenGL terminology, but D3D works the same way (since they’re both modelling the same hardware relationships). Vertex Shaders These are the second most complicated. They execute once for every input vertex… kinda. If you are using non-indexed rendering, then the ratio is … Read more
This was mostly covered by the comments, but in the interest of having an answer in place, let me summarize which pre-defined GLSL variables are gone in the core profile, and which are still there. In most cases, pre-defined variables were removed from core profile shaders as a direct consequence of large parts of the … Read more
Basically, you’re just implementing a spinlock. Only instead of one lock variable, you have an entire texture’s worth of locks. Logically, what you’re doing makes sense. But as far as OpenGL is concerned, this won’t actually work. See, the OpenGL shader execution model states that invocations execute in an order which is largely undefined relative … Read more
Here’s a basic GLUT example (written on OS X, adapt as needed) that generates two checkerboard textures, loads a shader with two samplers and combines them by tinting each (one red, one blue) and blending. See if this works for you: #include <stdio.h> #include <stdlib.h> #include <GLUT/glut.h> #include <OpenGL/gl.h> #include <OpenGL/glu.h> #define kTextureDim 64 GLuint … Read more
Hey, let’s slow down a bit here 🙂 Yes, that’s true that you receive the matrix by glGetFloatv(GL_MODELVIEW_MATRIX, ptr)… But that’s definitely not the thing you should do here! Let me explain: In GLSL, built-in variables like gl_ModelViewProjectionMatrix or functions like ftransform() are deprecated – that’s right, but that’s only because the whole matrix stack … Read more
From the OpenGL ES Shading Language reference: highp – 16-bit, floating point range: −262 to 262, integer range: −216 to 216 mediump – 10 bit, floating point range: −214 to 214, integer range: −210 to 210 lowp – 8 bit, floating point range: −2 to 2, integer range: −28 to 28 In OpenGL ES 3 … Read more
I am the author of the second implementation. It has always behaved correctly for me, but you wrote 2.9 / 6.9 instead of 2.0 / 6.0. Since you target GLSL, you should use conversion routines that are written with the GPU in mind: // All components are in the range [0…1], including hue. vec3 rgb2hsv(vec3 … Read more
The first thing you need to understand about shading_language_include is what it isn’t. It is not “I #include a file from the disk.” OpenGL doesn’t know what files are; it has no concept of the file system. Instead, you must pre-load all of the files you might want to include. So you have a shader … Read more