GLSL Details - vistone/cesium_Language_cn GitHub Wiki

Design and implementation ideas for our GLSL shader system.

Features

Auto #include functions, types, etc. starting with agi_. Most of these are in .glsl files, but some are prepended at runtime, but don’t have to be. Search for getBuiltinConstants in ShaderProgram.js.
In addition to auto includes, I suppose we need manual includes for things like SensorVolume.glsl, which are not global across Cesium, but useful for a few primitives.
Report useful line numbers from compile/link warning/errors.
Work well with uber-shaders determined at runtime. Search for getShaderProgram in CentralBody.js.
Work well with our material system, which dynamically creates shaders – think GLSL compile-time polymorphism. Each shader implementations a virtual function so-to-speak, e.g., see VerticalStripeMaterial and its shader, VerticalStripeMaterial.glsl. Anyone who can use a material calls this "virtual function." For a simple example, search for getShaderProgram in Polygon.js. A single primitive may have multiple materials for different surfaces (rendered in the same pass), so I rename uniforms like I am an out-of-order processor renaming registers. Search for combine in ComplexConicSensorVolume.js.
Control over precision used in the fragment shader. This is particularly important for mobile performance. See getShaderPrecisionFormat.
Consider GLSL minification.
Performance idea: async shader compile/link. Let's time linkProgram first because I think that is actually synchronous on most drivers.