| /* |
| The MIT License (MIT) |
| |
| Copyright (c) 2022 Sascha Willems |
| |
| Permission is hereby granted, free of charge, to any person obtaining a copy |
| of this software and associated documentation files (the "Software"), to deal |
| in the Software without restriction, including without limitation the rights |
| to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| copies of the Software, and to permit persons to whom the Software is |
| furnished to do so, subject to the following conditions: |
| |
| The above copyright notice and this permission notice shall be included in all |
| copies or substantial portions of the Software. |
| |
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
| SOFTWARE. |
| */ |
| |
| #version 450 |
| |
| layout(set = 0, binding = 0) uniform UBO |
| { |
| mat4 projection; |
| mat4 modelview; |
| vec4 lightPos; |
| vec4 frustumPlanes[6]; |
| float displacementFactor; |
| float tessellationFactor; |
| vec2 viewportDim; |
| float tessellatedEdgeSize; |
| } ubo; |
| |
| layout(set = 0, binding = 1) uniform sampler2D samplerHeight; |
| |
| layout (vertices = 4) out; |
| |
| layout (location = 0) in vec3 inNormal[]; |
| layout (location = 1) in vec2 inUV[]; |
| |
| layout (location = 0) out vec3 outNormal[4]; |
| layout (location = 1) out vec2 outUV[4]; |
| |
| // Calculate the tessellation factor based on screen space |
| // dimensions of the edge |
| float screenSpaceTessFactor(vec4 p0, vec4 p1) |
| { |
| // Calculate edge mid point |
| vec4 midPoint = 0.5 * (p0 + p1); |
| // Sphere radius as distance between the control points |
| float radius = distance(p0, p1) / 2.0; |
| |
| // View space |
| vec4 v0 = ubo.modelview * midPoint; |
| |
| // Project into clip space |
| vec4 clip0 = (ubo.projection * (v0 - vec4(radius, vec3(0.0)))); |
| vec4 clip1 = (ubo.projection * (v0 + vec4(radius, vec3(0.0)))); |
| |
| // Get normalized device coordinates |
| clip0 /= clip0.w; |
| clip1 /= clip1.w; |
| |
| // Convert to viewport coordinates |
| clip0.xy *= ubo.viewportDim; |
| clip1.xy *= ubo.viewportDim; |
| |
| // Return the tessellation factor based on the screen size |
| // given by the distance of the two edge control points in screen space |
| // and a reference (min.) tessellation size for the edge set by the application |
| return clamp(distance(clip0, clip1) / ubo.tessellatedEdgeSize * ubo.tessellationFactor, 1.0, 64.0); |
| } |
| |
| // Checks the current's patch visibility against the frustum using a sphere check |
| // Sphere radius is given by the patch size |
| bool frustumCheck() |
| { |
| // Fixed radius (increase if patch size is increased in example) |
| const float radius = 8.0f; |
| vec4 pos = gl_in[gl_InvocationID].gl_Position; |
| pos.y -= textureLod(samplerHeight, inUV[0], 0.0).r * ubo.displacementFactor; |
| |
| // Check sphere against frustum planes |
| for (int i = 0; i < 6; i++) { |
| if (dot(pos, ubo.frustumPlanes[i]) + radius < 0.0) |
| { |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| void main() |
| { |
| if (gl_InvocationID == 0) |
| { |
| if (!frustumCheck()) |
| { |
| gl_TessLevelInner[0] = 0.0; |
| gl_TessLevelInner[1] = 0.0; |
| gl_TessLevelOuter[0] = 0.0; |
| gl_TessLevelOuter[1] = 0.0; |
| gl_TessLevelOuter[2] = 0.0; |
| gl_TessLevelOuter[3] = 0.0; |
| } |
| else |
| { |
| if (ubo.tessellationFactor > 0.0) |
| { |
| gl_TessLevelOuter[0] = screenSpaceTessFactor(gl_in[3].gl_Position, gl_in[0].gl_Position); |
| gl_TessLevelOuter[1] = screenSpaceTessFactor(gl_in[0].gl_Position, gl_in[1].gl_Position); |
| gl_TessLevelOuter[2] = screenSpaceTessFactor(gl_in[1].gl_Position, gl_in[2].gl_Position); |
| gl_TessLevelOuter[3] = screenSpaceTessFactor(gl_in[2].gl_Position, gl_in[3].gl_Position); |
| gl_TessLevelInner[0] = mix(gl_TessLevelOuter[0], gl_TessLevelOuter[3], 0.5); |
| gl_TessLevelInner[1] = mix(gl_TessLevelOuter[2], gl_TessLevelOuter[1], 0.5); |
| } |
| else |
| { |
| // Tessellation factor can be set to zero by example |
| // to demonstrate a simple passthrough |
| gl_TessLevelInner[0] = 1.0; |
| gl_TessLevelInner[1] = 1.0; |
| gl_TessLevelOuter[0] = 1.0; |
| gl_TessLevelOuter[1] = 1.0; |
| gl_TessLevelOuter[2] = 1.0; |
| gl_TessLevelOuter[3] = 1.0; |
| } |
| } |
| |
| } |
| |
| gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position; |
| outNormal[gl_InvocationID] = inNormal[gl_InvocationID]; |
| outUV[gl_InvocationID] = inUV[gl_InvocationID]; |
| } |