Add shaders re-implemented in HLSL

These were written against the shaders at revision eddd724e7.
There have been changes made since then, which will need to be mirrored.

See `data/hlsl/README.md` for the current status of each sample.

data/hlsl/tessellation/pntriangles.tesc

@@ -0,0 +1,128 @@
+// Copyright 2020 Google LLC
+
+// PN patch data
+struct PnPatch
+{
+	float b210;
+	float b120;
+	float b021;
+	float b012;
+	float b102;
+	float b201;
+	float b111;
+	float n110;
+	float n011;
+	float n101;
+};
+
+// tessellation levels
+struct UBO
+{
+	float tessLevel;
+};
+
+cbuffer ubo : register(b0) { UBO ubo; }
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float3 Normal : NORMAL0;
+[[vk::location(1)]] float2 UV : TEXCOORD0;
+};
+
+struct HSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float3 Normal : NORMAL0;
+[[vk::location(3)]] float2 UV : TEXCOORD0;
+[[vk::location(6)]]	float pnPatch[10] : TEXCOORD6;
+};
+
+struct ConstantsHSOutput
+{
+    float TessLevelOuter[3] : SV_TessFactor;
+    float TessLevelInner : SV_InsideTessFactor;
+};
+
+void SetPnPatch(out float output[10], PnPatch patch)
+{
+	output[0] = patch.b210;
+	output[1] = patch.b120;
+	output[2] = patch.b021;
+	output[3] = patch.b012;
+	output[4] = patch.b102;
+	output[5] = patch.b201;
+	output[6] = patch.b111;
+	output[7] = patch.n110;
+	output[8] = patch.n011;
+	output[9] = patch.n101;
+}
+
+float wij(float4 iPos, float3 iNormal, float4 jPos)
+{
+	return dot(jPos.xyz - iPos.xyz, iNormal);
+}
+
+float vij(float4 iPos, float3 iNormal, float4 jPos, float3 jNormal)
+{
+	float3 Pj_minus_Pi = jPos.xyz
+					- iPos.xyz;
+	float3 Ni_plus_Nj  = iNormal+jNormal;
+	return 2.0*dot(Pj_minus_Pi, Ni_plus_Nj)/dot(Pj_minus_Pi, Pj_minus_Pi);
+}
+
+ConstantsHSOutput ConstantsHS(InputPatch<VSOutput, 3> patch, uint InvocationID : SV_PrimitiveID)
+{
+    ConstantsHSOutput output = (ConstantsHSOutput)0;
+	output.TessLevelOuter[0] = ubo.tessLevel;
+	output.TessLevelOuter[1] = ubo.tessLevel;
+	output.TessLevelOuter[2] = ubo.tessLevel;
+	output.TessLevelInner = ubo.tessLevel;
+    return output;
+}
+
+[domain("tri")]
+[partitioning("fractional_odd")]
+[outputtopology("triangle_ccw")]
+[outputcontrolpoints(3)]
+[patchconstantfunc("ConstantsHS")]
+[maxtessfactor(20.0f)]
+HSOutput main(InputPatch<VSOutput, 3> patch, uint InvocationID : SV_OutputControlPointID)
+{
+	HSOutput output = (HSOutput)0;
+	// get data
+	output.Pos = patch[InvocationID].Pos;
+	output.Normal = patch[InvocationID].Normal;
+	output.UV = patch[InvocationID].UV;
+
+	// set base
+	float P0 = patch[0].Pos[InvocationID];
+	float P1 = patch[1].Pos[InvocationID];
+	float P2 = patch[2].Pos[InvocationID];
+	float N0 = patch[0].Normal[InvocationID];
+	float N1 = patch[1].Normal[InvocationID];
+	float N2 = patch[2].Normal[InvocationID];
+
+	// compute control points
+	PnPatch pnPatch;
+	pnPatch.b210 = (2.0*P0 + P1 - wij(patch[0].Pos, patch[0].Normal, patch[1].Pos)*N0)/3.0;
+	pnPatch.b120 = (2.0*P1 + P0 - wij(patch[1].Pos, patch[1].Normal, patch[0].Pos)*N1)/3.0;
+	pnPatch.b021 = (2.0*P1 + P2 - wij(patch[1].Pos, patch[1].Normal, patch[2].Pos)*N1)/3.0;
+	pnPatch.b012 = (2.0*P2 + P1 - wij(patch[2].Pos, patch[2].Normal, patch[1].Pos)*N2)/3.0;
+	pnPatch.b102 = (2.0*P2 + P0 - wij(patch[2].Pos, patch[2].Normal, patch[0].Pos)*N2)/3.0;
+	pnPatch.b201 = (2.0*P0 + P2 - wij(patch[0].Pos, patch[0].Normal, patch[2].Pos)*N0)/3.0;
+	float E = ( pnPatch.b210
+			+ pnPatch.b120
+			+ pnPatch.b021
+			+ pnPatch.b012
+			+ pnPatch.b102
+			+ pnPatch.b201 ) / 6.0;
+	float V = (P0 + P1 + P2)/3.0;
+	pnPatch.b111 = E + (E - V)*0.5;
+	pnPatch.n110 = N0+N1-vij(patch[0].Pos, patch[0].Normal, patch[1].Pos, patch[1].Normal)*(P1-P0);
+	pnPatch.n011 = N1+N2-vij(patch[1].Pos, patch[1].Normal, patch[2].Pos, patch[2].Normal)*(P2-P1);
+	pnPatch.n101 = N2+N0-vij(patch[2].Pos, patch[2].Normal, patch[0].Pos, patch[0].Normal)*(P0-P2);
+	SetPnPatch(output.pnPatch, pnPatch);
+
+	return output;
+}