Aetheria/Assets/Shaders/Terrain/MyTessellation.cginc

#if !defined(TESSELLATION_INCLUDED)
#define TESSELLATION_INCLUDED

float _TessellationUniform;
float _TessellationEdgeLength;

struct TessellationControlPoint {
	float4 vertex : INTERNALTESSPOS;
	float3 normal : NORMAL;
	#if TESSELLATION_TANGENT
		float4 tangent : TANGENT;
	#endif
	float2 uv : TEXCOORD0;
	#if TESSELLATION_UV1
		float2 uv1 : TEXCOORD1;
	#endif
	#if TESSELLATION_UV2
		float2 uv2 : TEXCOORD2;
	#endif
};

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

TessellationControlPoint MyTessellationVertexProgram (VertexData v) {
	TessellationControlPoint p;
	p.vertex = v.vertex;
	p.normal = v.normal;
	#if TESSELLATION_TANGENT
		p.tangent = v.tangent;
	#endif
	p.uv = v.uv;
	#if TESSELLATION_UV1
		p.uv1 = v.uv1;
	#endif
	#if TESSELLATION_UV2
		p.uv2 = v.uv2;
	#endif
	return p;
}

bool TriangleIsBelowClipPlane (
	float3 p0, float3 p1, float3 p2, int planeIndex, float bias
) {
	float4 plane = unity_CameraWorldClipPlanes[planeIndex];
	return
		dot(float4(p0, 1), plane) < bias &&
		dot(float4(p1, 1), plane) < bias &&
		dot(float4(p2, 1), plane) < bias;
}

bool TriangleIsCulled (float3 p0, float3 p1, float3 p2, float bias) {
	return
		TriangleIsBelowClipPlane(p0, p1, p2, 0, bias) ||
		TriangleIsBelowClipPlane(p0, p1, p2, 1, bias) ||
		TriangleIsBelowClipPlane(p0, p1, p2, 2, bias) ||
		TriangleIsBelowClipPlane(p0, p1, p2, 3, bias);
}

float TessellationEdgeFactor (float3 p0, float3 p1) {
	#if defined(_TESSELLATION_EDGE)
		float edgeLength = distance(p0, p1);

		float3 edgeCenter = (p0 + p1) * 0.5;
		float viewDistance = distance(edgeCenter, _WorldSpaceCameraPos);

		return edgeLength * _ScreenParams.y /
			(_TessellationEdgeLength * viewDistance);
	#else
		return _TessellationUniform;
	#endif
}

#if !defined(MY_LIGHTING_INCLUDED)
uniform float3 _GridTransform;
#endif

float TessellationEdgeFactor (float2 p0, float2 p1) {
	#if defined(_TESSELLATION_EDGE)
		float edgeLength = distance(p0, p1);

		float2 edgeCenter = (p0 + p1) * 0.5;
		float viewDistance = distance(edgeCenter, _WorldSpaceCameraPos.xz);

		return edgeLength * _ScreenParams.y /
			(_TessellationEdgeLength * viewDistance);
	#else
		return _TessellationUniform;
	#endif
}

TessellationFactors MyPatchConstantFunction (
	InputPatch<TessellationControlPoint, 3> patch
) {
	//float3 p0 = mul(unity_ObjectToWorld, patch[0].vertex).xyz;
	//float3 p1 = mul(unity_ObjectToWorld, patch[1].vertex).xyz;
	//float3 p2 = mul(unity_ObjectToWorld, patch[2].vertex).xyz;
	float2 p0 = patch[0].vertex.xz * _GridTransform.z / 2 + _GridTransform.xy;
	float2 p1 = patch[1].vertex.xz * _GridTransform.z / 2 + _GridTransform.xy;
	float2 p2 = patch[2].vertex.xz * _GridTransform.z / 2 + _GridTransform.xy;
	TessellationFactors f;

	float bias = 500 * _DisplacementStrength;

	// if (TriangleIsCulled(p0, p1, p2, bias)) {
	// 	f.edge[0] = f.edge[1] = f.edge[2] = f.inside = 0;
	// }
	// else {
	    f.edge[0] = TessellationEdgeFactor(p1, p2);
	    f.edge[1] = TessellationEdgeFactor(p2, p0);
	    f.edge[2] = TessellationEdgeFactor(p0, p1);
		f.inside =
			(TessellationEdgeFactor(p1, p2) +
			TessellationEdgeFactor(p2, p0) +
			TessellationEdgeFactor(p0, p1)) * (1 / 3.0);
	// }
	return f;
}

[UNITY_domain("tri")]
[UNITY_outputcontrolpoints(3)]
[UNITY_outputtopology("triangle_cw")]
[UNITY_partitioning("fractional_even")]
[UNITY_patchconstantfunc("MyPatchConstantFunction")]
TessellationControlPoint MyHullProgram (
	InputPatch<TessellationControlPoint, 3> patch,
	uint id : SV_OutputControlPointID
) {
	return patch[id];
}

[UNITY_domain("tri")]
InterpolatorsVertex MyDomainProgram (
	TessellationFactors factors,
	OutputPatch<TessellationControlPoint, 3> patch,
	float3 barycentricCoordinates : SV_DomainLocation
) {
	VertexData data;

	#define MY_DOMAIN_PROGRAM_INTERPOLATE(fieldName) data.fieldName = \
		patch[0].fieldName * barycentricCoordinates.x + \
		patch[1].fieldName * barycentricCoordinates.y + \
		patch[2].fieldName * barycentricCoordinates.z;

	MY_DOMAIN_PROGRAM_INTERPOLATE(vertex)
	MY_DOMAIN_PROGRAM_INTERPOLATE(normal)
	#if TESSELLATION_TANGENT
		MY_DOMAIN_PROGRAM_INTERPOLATE(tangent)
	#endif
	MY_DOMAIN_PROGRAM_INTERPOLATE(uv)
	#if TESSELLATION_UV1
		MY_DOMAIN_PROGRAM_INTERPOLATE(uv1)
	#endif
	#if TESSELLATION_UV2
		MY_DOMAIN_PROGRAM_INTERPOLATE(uv2)
	#endif

	return MyVertexProgram(data);
}

#endif