Shader

The Rasterization Rendering Pipeline

The polyred package offers a customized rendering pipeline:

                Vertex Generation                  
                       |                           
                       v                           
                 Vertex Shading                    
                       |                           
                       v                           
               Fragment Generation                 
                       |                           
                       v                           
                Fragment Shading                   

with the following basic passes:

package render

type Renderer struct {
    // contains unexported fields
}

// DrawPrimitives is a pass that executes Draw call concurrently on all
// given triangle primitives, and draws all geometric and rendering
// information on the given buffer. This primitive uses supplied shader
// programs (i.e. currently supports vertex shader and fragment shader)
//
// See shader.Program for more information regarding shader programming.
func (r *Renderer) DrawPrimitives(buf *buffer.Buffer, idx []uint64, verts []*primitive.Vertex, p shader.VertexProgram)

// DrawFragments is a concurrent executor of the given shader that travel
// through all fragments. Each fragment executes the given shaders exactly once.
//
// One should not manipulate the given image buffer in the shader.
// Instead, return the resulting color in the shader can avoid data race.
func (r *Renderer) DrawFragments(buf *buffer.Buffer, funcs ...shader.FragmentProgram)

Primitives

TODO: vertex and fragment

Shader Basics

A shader is an interface that implements the VertexShader and FragmentShader methods:

package shader

type Program interface {
	VertexShader(primitive.Vertex) primitive.Vertex
	FragmentShader(primitive.Fragment) color.RGBA
}

A VertexShader consumes a vertex and returns a transformed vertex. The input and output vertex may convey different information. The information stored in a vertex primitive will be interpolated depending on the specified camera target. An orthographic camera will interpolate vertex attributes linearly and the interpolation of a perspective camera is, of course, perspective corrected.

TODO: more about varying in vertex and fragment, smooth and flat.

License

Copyright © 2021 Changkun Ou. All rights reserved.