Geometry Shader Cookbook

The repository is the practice project of Geometry shader in Unity engine.

Define the Method of Geometry Shader

#pragma geometry geom

Define Data Structure

//The data structure from the application to the vertex shader.
struct a2v  
{  
    float4 vertex : POSITION;  
    float2 uv : TEXCOORD0;  
};  

//The data structure from the vertex shader to the geometry shader.
struct v2g  
{  
    float4 vertex : POSITION;  
    float2 uv : TEXCOORD0;  
};

//The data structure from the geometry shader to the fragment shader.
struct g2f
{  
    float4 vertex : SV_POSITION;  
    float2 uv : TEXCOORD0;
};  

Write Geometry Shader

  [maxvertexcount(3)]  
  void geom(triangle v2g input[3], inout TriangleStream<g2f> outStream)  
  {  
        g2f o;  

        for(int i = 0; i < 3; i++)  
        {  
              o.vertex = UnityObjectToClipPos(input[i].vertex);  
              o.uv = input[i].uv;  
              outStream.Append(o);  
        }  
  
        outStream.RestartStrip();  
  }

Attribute
maxvertexcount(number)	The output vertex number for the geometry shader.

Inputs
point	The point pritimive data.
line	The line pritimive data.
lineadj	The line pritimive data, including the adjacent line pritimive data.
triangle	The triangle pritimive data.
triangleadj	The triangle pritimive data, including the adjacent triangle pritimive data.

Outputs
PointStream	The point stream data.
LineStream	The line stream data.
TriangleStream	The triangle stream data.

Stream Methods
Append(struct)	The method to add the data.
RestartStrip()	If the output is TriangleStream, you need to call the method to form the triangle. (Three vertices form a triangle)

Implement Examples

PointStream/Vertex

LineStream/Line

TriangleStream/DoNothing

TriangleStream/ExtrudeVertex

TriangleStream/TriangleAnimation

TriangleStream/ExtrudePyramid

TriangleStream/ExtrudePyramidAnimation

TriangleStream/ExtrudeTriangle

TriangleStream/ExtrudeTriangleAnimation