Material Assets

This document intends to describe the process of loading user declared shaders and materials and transforming them into usable resources.

Assets

Materials are declared by the user as a JSON, specifying the material type and references to shaders.

{
	"domain":"World",
	"type": "Surface",
	"shaders": {
		"Fragment": "../.."
	},
	"variables": [
		{
			"name":"color",
			"data_type": "vec4f",
			"value":"Purple",
			"type":"Static"
		}
	]
}

Materials can also reference other materials as their parent to inherit all their characteristics but they can alter values of variables declared in the parent.

{
	"parent":"material",
	"variables": [
		{
			"name": "color",
			"value": "Red"
		}
	]
}

The engine can use this relationship for optimization. If the shader is the same and only variable values change, the engine can treat the variants as the same pipeline with different per-instance uniform values.

Do not rely on that optimization as a stable behavior. The engine may increase shader or pipeline permutations when static replacement would produce better runtime code.

Pipeline

Loading

When a load request is performed in the code, the material/variant is first loaded, shaders are then fetched from there, once all assets are loaded, processing starts.

Our objective is to produce shader code and metadata that can be used by a render model during runtime to produce the intended results.

flowchart TD

ma ---> Materials --> Shaders

subgraph Materials
Material
end

subgraph Shaders
Vertex
Fragment
...
end

shader_manager[[Shader Manager]]

Materials ---> shader_manager
Shaders ---> shader_manager

render_model_a[Visibility]
render_model_b[Forward]

shader_manager ---> render_model_a
shader_manager ---> render_model_b

subgraph Resources
	subgraph resources.materials[Materials]
		Material
	end

	subgraph resource.shaders[Shaders]
	Compute
	end
end

render_model_a ---> Resources

Generated materials are tagged by render model.

{
	"name":"material",
	"model": {
		"name":"Visibility",
		"pass":"MaterialEvaluation",
	},
	"variables": [
		{
			"name": "color",
			"type": "Static",
			"data_type": "vec4f",
			"value": "Purple",
		}
	]
	...
}

Variables are also defined/extracted from the code.

Generation

Generation details are not complete yet. This section will describe how material declarations become render-model-specific shader code and metadata.