GLSL Specifics

GLSL shaders used by the PlayCanvas engine must satisfy certain requirements. These requirements allow the engine to correctly integrate shaders, ensuring they receive the necessary resources such as attributes, uniforms, and varyings. Following these rules also allows us to automatically process the shader for slightly different requirements when transpiling to WGSL for use with WebGPU.

The following sections outline key aspects of writing GLSL shaders for PlayCanvas.

注記

#version should not be included in the shader source. PlayCanvas automatically adds the appropriate version directive based on whether WebGL2 or WebGPU is targeted.

Attributes

Attributes define per-vertex input data. They must be declared using the following syntax:

attribute vec2 aUv0;

The attribute name must match the name specified in the attributes property when creating the ShaderMaterial.

注記

The in keyword (introduced in GLSL 3.3+) is not supported.

Uniforms

Uniforms are used to pass resources from the engine to the shader. They are declared in the standard way for numerical and texture uniforms:

uniform vec3 view_position;

The engine automatically sets appropriate uniform values when rendering.

Varyings

Varyings are used to pass values from the vertex shader to the fragment shader. They must be declared using standard GLSL syntax:

varying vec2 uv0;

注記

The in/out syntax (introduced in GLSL 3.3+) is not supported.