1/* 2The MIT License (MIT) 3 4Copyright (c) 2022 Google LLC 5Copyright (c) 2022 Sascha Willems 6 7Permission is hereby granted, free of charge, to any person obtaining a copy 8of this software and associated documentation files (the "Software"), to deal 9in the Software without restriction, including without limitation the rights 10to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 11copies of the Software, and to permit persons to whom the Software is 12furnished to do so, subject to the following conditions: 13 14The above copyright notice and this permission notice shall be included in all 15copies or substantial portions of the Software. 16 17THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 18IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 19FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 20AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 21LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 22OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 23SOFTWARE. 24*/ 25 26struct UBO 27{ 28 float4x4 projection; 29 float4x4 modelview; 30 float4 lightPos; 31 float4 frustumPlanes[6]; 32 float displacementFactor; 33 float tessellationFactor; 34 float2 viewportDim; 35 float tessellatedEdgeSize; 36}; 37cbuffer ubo : register(b0) { UBO ubo; }; 38 39Texture2D textureHeight : register(t1); 40SamplerState samplerHeight : register(s1); 41 42struct VSOutput 43{ 44 float4 Pos : SV_POSITION; 45[[vk::location(0)]] float3 Normal : NORMAL0; 46[[vk::location(1)]] float2 UV : TEXCOORD0; 47}; 48 49struct HSOutput 50{ 51[[vk::location(2)]] float4 Pos : SV_POSITION; 52[[vk::location(0)]] float3 Normal : NORMAL0; 53[[vk::location(1)]] float2 UV : TEXCOORD0; 54}; 55 56struct ConstantsHSOutput 57{ 58 float TessLevelOuter[4] : SV_TessFactor; 59 float TessLevelInner[2] : SV_InsideTessFactor; 60}; 61 62// Calculate the tessellation factor based on screen space 63// dimensions of the edge 64float screenSpaceTessFactor(float4 p0, float4 p1) 65{ 66 // Calculate edge mid point 67 float4 midPoint = 0.5 * (p0 + p1); 68 // Sphere radius as distance between the control points 69 float radius = distance(p0, p1) / 2.0; 70 71 // View space 72 float4 v0 = mul(ubo.modelview, midPoint); 73 74 // Project into clip space 75 float4 clip0 = mul(ubo.projection, (v0 - float4(radius, float3(0.0, 0.0, 0.0)))); 76 float4 clip1 = mul(ubo.projection, (v0 + float4(radius, float3(0.0, 0.0, 0.0)))); 77 78 // Get normalized device coordinates 79 clip0 /= clip0.w; 80 clip1 /= clip1.w; 81 82 // Convert to viewport coordinates 83 clip0.xy *= ubo.viewportDim; 84 clip1.xy *= ubo.viewportDim; 85 86 // Return the tessellation factor based on the screen size 87 // given by the distance of the two edge control points in screen space 88 // and a reference (min.) tessellation size for the edge set by the application 89 return clamp(distance(clip0, clip1) / ubo.tessellatedEdgeSize * ubo.tessellationFactor, 1.0, 64.0); 90} 91 92// Checks the current's patch visibility against the frustum using a sphere check 93// Sphere radius is given by the patch size 94bool frustumCheck(float4 Pos, float2 inUV) 95{ 96 // Fixed radius (increase if patch size is increased in example) 97 const float radius = 8.0f; 98 float4 pos = Pos; 99 pos.y -= textureHeight.SampleLevel(samplerHeight, inUV, 0.0).r * ubo.displacementFactor; 100 101 // Check sphere against frustum planes 102 for (int i = 0; i < 6; i++) { 103 if (dot(pos, ubo.frustumPlanes[i]) + radius < 0.0) 104 { 105 return false; 106 } 107 } 108 return true; 109} 110 111ConstantsHSOutput ConstantsHS(InputPatch<VSOutput, 4> patch) 112{ 113 ConstantsHSOutput output = (ConstantsHSOutput)0; 114 115 if (!frustumCheck(patch[0].Pos, patch[0].UV)) 116 { 117 output.TessLevelInner[0] = 0.0; 118 output.TessLevelInner[1] = 0.0; 119 output.TessLevelOuter[0] = 0.0; 120 output.TessLevelOuter[1] = 0.0; 121 output.TessLevelOuter[2] = 0.0; 122 output.TessLevelOuter[3] = 0.0; 123 } 124 else 125 { 126 if (ubo.tessellationFactor > 0.0) 127 { 128 output.TessLevelOuter[0] = screenSpaceTessFactor(patch[3].Pos, patch[0].Pos); 129 output.TessLevelOuter[1] = screenSpaceTessFactor(patch[0].Pos, patch[1].Pos); 130 output.TessLevelOuter[2] = screenSpaceTessFactor(patch[1].Pos, patch[2].Pos); 131 output.TessLevelOuter[3] = screenSpaceTessFactor(patch[2].Pos, patch[3].Pos); 132 output.TessLevelInner[0] = lerp(output.TessLevelOuter[0], output.TessLevelOuter[3], 0.5); 133 output.TessLevelInner[1] = lerp(output.TessLevelOuter[2], output.TessLevelOuter[1], 0.5); 134 } 135 else 136 { 137 // Tessellation factor can be set to zero by example 138 // to demonstrate a simple passthrough 139 output.TessLevelInner[0] = 1.0; 140 output.TessLevelInner[1] = 1.0; 141 output.TessLevelOuter[0] = 1.0; 142 output.TessLevelOuter[1] = 1.0; 143 output.TessLevelOuter[2] = 1.0; 144 output.TessLevelOuter[3] = 1.0; 145 } 146 } 147 148 return output; 149} 150 151[domain("quad")] 152[partitioning("integer")] 153[outputtopology("triangle_cw")] 154[outputcontrolpoints(4)] 155[patchconstantfunc("ConstantsHS")] 156[maxtessfactor(20.0f)] 157HSOutput main(InputPatch<VSOutput, 4> patch, uint InvocationID : SV_OutputControlPointID) 158{ 159 HSOutput output = (HSOutput)0; 160 output.Pos = patch[InvocationID].Pos; 161 output.Normal = patch[InvocationID].Normal; 162 output.UV = patch[InvocationID].UV; 163 return output; 164} 165