CustomTessellation.hlsl

#if defined(SHADER_API_D3D11) || defined(SHADER_API_GLES3) || defined(SHADER_API_GLCORE) || defined(SHADER_API_VULKAN) || defined(SHADER_API_METAL) || defined(SHADER_API_PSSL)
#define UNITY_CAN_COMPILE_TESSELLATION 1
#   define UNITY_domain                 domain
#   define UNITY_partitioning           partitioning
#   define UNITY_outputtopology         outputtopology
#   define UNITY_patchconstantfunc      patchconstantfunc
#   define UNITY_outputcontrolpoints    outputcontrolpoints
#endif



// The structure definition defines which variables it contains.
// This example uses the Attributes structure as an input structure in
// the vertex shader.

// vertex to fragment struct
struct Varyings
{
    float4 color : COLOR;
    float3 normal : NORMAL;
    float4 vertex : SV_POSITION;
    float2 uv : TEXCOORD0;
};


// tessellation data
struct TessellationFactors
{
    float edge[3] : SV_TessFactor;
    float inside : SV_InsideTessFactor;
};

// Extra vertex struct
struct ControlPoint
{
    float4 vertex : INTERNALTESSPOS;
    float2 uv : TEXCOORD0;
    float4 color : COLOR;
    float3 normal : NORMAL;
};

// the original vertex struct
struct Attributes
{
    float4 vertex : POSITION;
    float3 normal : NORMAL;
    float2 uv : TEXCOORD0;
    float4 color : COLOR;

};

// tessellation variables, add these to your shader properties
float _Tess;
float _MaxTessDistance;

// info so the GPU knows what to do (triangles) and how to set it up , clockwise, fractional division
// hull takes the original vertices and outputs more
[UNITY_domain("tri")]
[UNITY_outputcontrolpoints(3)]
[UNITY_outputtopology("triangle_cw")]
[UNITY_partitioning("fractional_odd")]
//[UNITY_partitioning("fractional_even")]
//[UNITY_partitioning("pow2")]
//[UNITY_partitioning("integer")]
[UNITY_patchconstantfunc("patchConstantFunction")]
ControlPoint hull(InputPatch<ControlPoint, 3> patch, uint id : SV_OutputControlPointID)
{
    return patch[id];
}


// fade tessellation at a distance
float CalcDistanceTessFactor(float4 vertex, float minDist, float maxDist, float tess)
{
    float3 worldPosition = TransformObjectToWorld(vertex.xyz);
    float dist = distance(worldPosition, _WorldSpaceCameraPos);
    float f = clamp(1.0 - (dist - minDist) / (maxDist - minDist), 0.01, 1.0) * tess;
    return (f);
}


// tessellation
TessellationFactors patchConstantFunction(InputPatch<ControlPoint, 3> patch)
{
    // values for distance fading the tessellation
    float minDist = 5.0;
    float maxDist = _MaxTessDistance;

    TessellationFactors f;

    float edge0 = CalcDistanceTessFactor(patch[0].vertex, minDist, maxDist, _Tess);
    float edge1 = CalcDistanceTessFactor(patch[1].vertex, minDist, maxDist, _Tess);
    float edge2 = CalcDistanceTessFactor(patch[2].vertex, minDist, maxDist, _Tess);

    // make sure there are no gaps between different tessellated distances, by averaging the edges out.
    f.edge[0] = (edge1 + edge2) / 2;
    f.edge[1] = (edge2 + edge0) / 2;
    f.edge[2] = (edge0 + edge1) / 2;
    f.inside = (edge0 + edge1 + edge2) / 3;
    return f;
}

// second vertex, copy to shader
//Varyings vert(Attributes input)
//{
//  Varyings output;
//  // put your vertex manipulation here , ie: input.vertex.xyz += distortiontexture
//  output.vertex = TransformObjectToHClip(input.vertex.xyz);
//  output.color = input.color;
//  output.normal = input.normal;
//  output.uv = input.uv;
//  return output;
//}

// domain, copy to shader
//[UNITY_domain("tri")]
//Varyings domain(TessellationFactors factors, OutputPatch<ControlPoint, 3> patch, float3 barycentricCoordinates : SV_DomainLocation)
//{
//  Attributes v;
//
//#define Tesselationing(fieldName) v.fieldName = \
//              patch[0].fieldName * barycentricCoordinates.x + \
//              patch[1].fieldName * barycentricCoordinates.y + \
//              patch[2].fieldName * barycentricCoordinates.z;
//
//  Tesselationing(vertex)
//      Tesselationing(uv)
//      Tesselationing(color)
//      Tesselationing(normal)
//
//      return vert(v);
//}