Shader Coding - Best Practices: Difference between revisions

Jump to navigation Jump to search
mNo edit summary
 
(10 intermediate revisions by one other user not shown)
Line 1: Line 1:
{{WIP|Will be based on: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg35934.html}}
{{WIP|Will be based on: http://www.mail-archive.com/flightgear-devel@lists.sourceforge.net/msg35934.html}}
{{Rendering}}
== File Header ==
{{Note|It's a good idea to add a header to each shader detailing:
* filename
* purpose
* license
* author
* rendering pipeline (rembrandt/default)
* description
<syntaxhighlight lang="glsl">
// -*- mode: C; -*-
// urban.frag
// Licence: GPL v2
// Author: Frederic Bouvier.
//  Adapted from the paper by F. Policarpo et al. : Real-time Relief Mapping on Arbitrary Polygonal Surfaces
//  Adapted from the paper and sources by M. Drobot in GPU Pro : Quadtree Displacement Mapping with Height Blending
</syntaxhighlight>
}}
== Supported GLSL Versions ==
{{Note|Be aware that we currently '''_DO_NOT_''' support glsl <nowiki>> 1.2x. Please don't mix '''glsl''' flavours: please stick to glsl 1.2x.(even though support for it is largely </nowiki>''deprecated''). The transition to OpenGL 3.0 / glsl <nowiki>>=1.3x is a very big undertaking, and not backward compatible. It is always a good idea to declare the expected GLSL version at the top of each file</nowiki>:
<syntaxhighlight lang="glsl">
#version 120
</syntaxhighlight>
}}
== Enabling Extensions ==
{{Note|:To enable vendor specific extensions, use the '''#extension''' pragma at the top of the file, for example:
<syntaxhighlight lang="glsl">
#extension GL_ATI_shader_texture_lod : enable
#extension GL_ARB_shader_texture_lod : enable
</syntaxhighlight>
}}


== Vertex Shaders ==
== Vertex Shaders ==
Line 11: Line 47:
</syntaxhighlight>
</syntaxhighlight>
}}
}}


== Fragment Shaders ==
== Fragment Shaders ==


{{Note|To check if your shader is working, add this as the last line, it should turn all pixels black:
{{Note|To check if your shader is working, use a trivial  shader like this one or just add the last line to the end of the shader, it should turn all pixels black:
<syntaxhighlight lang="glsl">
<syntaxhighlight lang="glsl">
#version 120
void main() {
// turn all pixels into  black
gl_FragColor = vec4 (0.0,0.0,0.0,1.0);
gl_FragColor = vec4 (0.0,0.0,0.0,1.0);
}
</syntaxhighlight>
}}
{{Note|if4dnf: it's usually bad practice to do any kind of operations on gl_FragColor assignment. At most a vec4() swizzle is ''accepted'', although even that one is treated differently based on the platform (some assign a temporary variable, some don't). Do wahtever you need in a separate vec4 variable and just assign it's value to gl_FragColor at the end.}}
{{Note|If the fragment isn't running, there should be an error message in the log file (I wish they'd still be written to the console). Might be that the texture isn't defined in the supporting framework for instance - the shader assumed that it is available, but you need to declare it in the matching C++ code/effect file first.}}
{{Note|This is how you can make a pixel darker:
<syntaxhighlight lang="glsl">
gl_FragColor = color * 0.5;
</syntaxhighlight>
</syntaxhighlight>
}}
}}
[[Category:Shader development]]
574

edits

Navigation menu