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shaders/mesh_shader_culling/mesh_shader_culling.task

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+#version 450
+/* Copyright (c) 2023-2025, Holochip Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 the "License";
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#extension GL_EXT_mesh_shader: require
+#extension GL_GOOGLE_include_directive: require
+#extension GL_KHR_shader_subgroup_ballot : require                  // subgroupBallot, subgroupBallotBitCount, subgroupBallotExclusiveBitCount
+
+#include "mesh_shader_shared.h"
+
+// Use numTaskInvocationsX * numTaskInvocationsY task shader invocations per task shader workgroup,
+// resulting in N * N * numTaskInvocationsX * numTaskInvocationsY invocations
+layout(local_size_x = numTaskInvocationsX, local_size_y = numTaskInvocationsY, local_size_z = 1) in;
+
+layout (binding = 0) uniform UBO
+{
+    float cull_center_x;
+    float cull_center_y;
+    float cull_radius;
+    float meshlet_density;
+} ubo;
+
+taskPayloadSharedEXT SharedData sharedData;
+
+float square(float x)
+{
+    return x * x;
+}
+
+float square(vec2 p )
+{
+    return p.x * p.x + p.y * p.y;
+}
+
+void main()
+{
+    // calculate size and offset of sub-rect per task shader invocation
+    vec2 size = 2.0f / ( gl_NumWorkGroups.xy * gl_WorkGroupSize.xy );
+    vec2 offset = gl_GlobalInvocationID.xy * size;
+
+    // determine the four corners of the sub-rect and check if it's completely out of the culling circle
+    // (ignoring the case that a sub-rect could completely include the culling circle...)
+
+    vec2 position = vec2(ubo.cull_center_x, ubo.cull_center_y);
+    vec2 p0 = position + offset;
+    vec2 p1 = p0 + vec2(size.x, 0.0f);
+    vec2 p2 = p0 + size;
+    vec2 p3 = p0 + vec2(0.0f, size.y);
+    float squaredRadius = square(ubo.cull_radius);
+    bool isValid = ( square(p0) < squaredRadius )
+                    && ( square(p1) < squaredRadius )
+                    && ( square(p2) < squaredRadius)
+                    && ( square(p3) < squaredRadius);
+    // contribute a single bit by this task shader invocation
+    uvec4 validVotes = subgroupBallot(isValid);
+
+    if ( isValid )
+    {
+        // get the next free index into the offsets array
+        uint index = subgroupBallotExclusiveBitCount(validVotes);
+        sharedData.offsets[index] = offset;
+    }
+    if ( gl_LocalInvocationIndex == 0 )
+    {
+        // for just one task shader invocation we can emit mesh shaders
+        sharedData.position = position;
+        sharedData.size = size;
+        // get the actual number of task shader invocations that are determined to display something
+        uint validCount = subgroupBallotBitCount(validVotes);
+        EmitMeshTasksEXT(validCount, 1, 1);
+    }
+}