shaders

Overview ¶

Package shaders provides a ShaderMaterial.Instance with the shader pipeline written within Go.

Shaders are multi-stage programs executed on the GPU. They can be used to gain precise control over rendering calculations, such as lighting, shadows, and post-processing effects.

To create a new 2D shader in Go, define a struct that embeds shaders.Type2D and implements the pipeline methods you would like to overide. For example:

type MyShader struct {
	CanvasItem.Shader
}

// The pipeline functions are named after what they return, not what they accept as
// input.

// Fragment runs for each point/vertex of the shape/mesh being rendered, should return
// fragment parameters for each point (also known as a vertex shader).
func (MyShader) Fragment(vertex CanvasItem.Vertex) CanvasItem.Fragment {
	return CanvasItem.Fragment{
		Position: vertex.Position,
	}
}

// Material runs for each pixel on each face of the shape being rendered, should return
// the surface parameters for each pixel (also known as a fragment shader). The input
// fragment is a blend of each contributing vertex point.
func (MyShader) Material(fragment CanvasItem.Fragment) CanvasItem.Material {
	return CanvasItem.Material{
		Color: rgba.New(1, 0, 0, 1),
	}
}

// Lighting runs for each light, per pixel for each face of the shape being rendered, should
// return the final color for each pixel (also known as a lighting pass).
func (MyShader) Lighting(material CanvasItem.Material) CanvasItem.Lighting {
	return CanvasItem.Lighting{
		Color: material.Color,
	}
}

Each sub-package provides GPU-specific shader types that can be used within a shader pipeline. Keep in mind that the Go code is compiled to run on the GPU, so non-GPU values, function calls or branches will only take affect during compilation and not when rendering.

All for loops will be unrolled. The shaders package does not currently support non-constant loops.

Uniforms ¶

Uniforms are added as fields to the shader struct. They can be written with Set and read with Get. Uniforms wrapped inside the PerInstance generic type need to be accessed through the RenderingServer/GeometryInstance3D packages.

type MyShader struct {
	CanvasItem.Shader[MyShader]

	MyUniform vec2.XY `gd:"my_uniform"`

	Color shaders.PerInstance[vec4.XYZW] `gd:"color"`
}

var shader = new(MyShader)
shaders.Compile(&shader)
shaders.Set(&shader.MyUniform, Vector2.New(1, 2))