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Converting GLSL to Godot shaders¶
This document explains the differences between Godot's shading language and GLSL and gives practical advice on how to migrate shaders from other sources, such as Shadertoy and The Book of Shaders, into Godot shaders.
For detailed information on Godot's shading language, please refer to the Shading Language reference.
Godot uses a shading language based on GLSL with the addition of a few quality-of-life features. Accordingly, most features available in GLSL are available in Godot's shading language.
In GLSL, each shader uses a separate program. You have one program for the
vertex shader and one for the fragment shader. In Godot, you have a single
shader that contains a
vertex and/or a
fragment function. If you only
choose to write one, Godot will supply the other.
Godot allows uniform variables and functions to be shared by defining the fragment and vertex shaders in one file. In GLSL, the vertex and fragment programs cannot share variables except when varyings are used.
In GLSL, you can pass in per-vertex information using attributes and have the
flexibility to pass in as much or as little as you want. In Godot, you have a
set number of input attributes, including
NORMAL. Each shaders' page in the shader reference section
of the documentation comes with a complete list of its vertex attributes.
gl_Position receives the final position of a vertex specified in the vertex
shader. It is specified by the user in clip space. Typically, in GLSL, the model
space vertex position is passed in using a vertex attribute called
and you handle the conversion from model space to clip space manually.
VERTEX specifies the vertex position in model space at the
beginning of the
vertex function. Godot also handles the final conversion to
clip space after the user-defined
vertex function is run. If you want to
skip the conversion from model to view space, you can set the
skip_vertex_transform. If you want to skip all transforms, set
skip_vertex_transform and set the
mat4(1.0) in order to nullify the final transform from view space to clip
Varyings are a type of variable that can be passed from the vertex shader to the
fragment shader. In modern GLSL (3.0 and up), varyings are defined with the
out keywords. A variable going out of the vertex shader is
out in the vertex shader and
in inside the fragment shader.
In GLSL, each shader program looks like a self-contained C-style program.
Accordingly, the main entry point is
main. If you are copying a vertex
vertex and if you are copying a fragment shader,
The Godot shader preprocessor supports the following macros:
.gdshaderinc files and with a maximum depth of 25)
#pragma disable_preprocessor, which disables preprocessing fo