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.tese

@@ -0,0 +1,126 @@
+// 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;
+};
+
+struct UBO
+{
+    float4x4 projection;
+    float4x4 model;
+    float tessAlpha;
+};
+
+cbuffer ubo : register(b1) { UBO ubo; }
+
+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;
+};
+
+struct DSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float3 Normal : NORMAL0;
+[[vk::location(1)]] float2 UV : TEXCOORD0;
+};
+
+#define uvw TessCoord
+
+PnPatch GetPnPatch(float pnPatch[10])
+{
+    PnPatch output;
+    output.b210 = pnPatch[0];
+	output.b120 = pnPatch[1];
+	output.b021 = pnPatch[2];
+	output.b012 = pnPatch[3];
+	output.b102 = pnPatch[4];
+	output.b201 = pnPatch[5];
+	output.b111 = pnPatch[6];
+	output.n110 = pnPatch[7];
+	output.n011 = pnPatch[8];
+	output.n101 = pnPatch[9];
+    return output;
+}
+
+[domain("tri")]
+DSOutput main(ConstantsHSOutput input, float3 TessCoord : SV_DomainLocation, const OutputPatch<HSOutput, 3> patch)
+{
+    PnPatch pnPatch[3];
+    pnPatch[0] = GetPnPatch(patch[0].pnPatch);
+    pnPatch[1] = GetPnPatch(patch[1].pnPatch);
+    pnPatch[2] = GetPnPatch(patch[2].pnPatch);
+
+    DSOutput output = (DSOutput)0;
+    float3 uvwSquared = uvw * uvw;
+    float3 uvwCubed   = uvwSquared * uvw;
+
+    // extract control points
+    float3 b210 = float3(pnPatch[0].b210, pnPatch[1].b210, pnPatch[2].b210);
+    float3 b120 = float3(pnPatch[0].b120, pnPatch[1].b120, pnPatch[2].b120);
+    float3 b021 = float3(pnPatch[0].b021, pnPatch[1].b021, pnPatch[2].b021);
+    float3 b012 = float3(pnPatch[0].b012, pnPatch[1].b012, pnPatch[2].b012);
+    float3 b102 = float3(pnPatch[0].b102, pnPatch[1].b102, pnPatch[2].b102);
+    float3 b201 = float3(pnPatch[0].b201, pnPatch[1].b201, pnPatch[2].b201);
+    float3 b111 = float3(pnPatch[0].b111, pnPatch[1].b111, pnPatch[2].b111);
+
+    // extract control normals
+    float3 n110 = normalize(float3(pnPatch[0].n110, pnPatch[1].n110, pnPatch[2].n110));
+    float3 n011 = normalize(float3(pnPatch[0].n011, pnPatch[1].n011, pnPatch[2].n011));
+    float3 n101 = normalize(float3(pnPatch[0].n101, pnPatch[1].n101, pnPatch[2].n101));
+
+    // compute texcoords
+    output.UV  = TessCoord[2]*patch[0].UV + TessCoord[0]*patch[1].UV + TessCoord[1]*patch[2].UV;
+
+    // normal
+    // Barycentric normal
+    float3 barNormal = TessCoord[2]*patch[0].Normal + TessCoord[0]*patch[1].Normal + TessCoord[1]*patch[2].Normal;
+    float3 pnNormal  = patch[0].Normal*uvwSquared[2] + patch[1].Normal*uvwSquared[0] + patch[2].Normal*uvwSquared[1]
+                   + n110*uvw[2]*uvw[0] + n011*uvw[0]*uvw[1]+ n101*uvw[2]*uvw[1];
+    output.Normal = ubo.tessAlpha*pnNormal + (1.0-ubo.tessAlpha) * barNormal;
+
+    // compute interpolated pos
+    float3 barPos = TessCoord[2]*patch[0].Pos.xyz
+                + TessCoord[0]*patch[1].Pos.xyz
+                + TessCoord[1]*patch[2].Pos.xyz;
+
+    // save some computations
+    uvwSquared *= 3.0;
+
+    // compute PN position
+    float3 pnPos  = patch[0].Pos.xyz*uvwCubed[2]
+                + patch[1].Pos.xyz*uvwCubed[0]
+                + patch[2].Pos.xyz*uvwCubed[1]
+                + b210*uvwSquared[2]*uvw[0]
+                + b120*uvwSquared[0]*uvw[2]
+                + b201*uvwSquared[2]*uvw[1]
+                + b021*uvwSquared[0]*uvw[1]
+                + b102*uvwSquared[1]*uvw[2]
+                + b012*uvwSquared[1]*uvw[0]
+                + b111*6.0*uvw[0]*uvw[1]*uvw[2];
+
+    // final position and normal
+    float3 finalPos = (1.0-ubo.tessAlpha)*barPos + ubo.tessAlpha*pnPos;
+    output.Pos = mul(ubo.projection, mul(ubo.model, float4(finalPos,1.0)));
+    return output;
+}