VK_HUAWEI_cluster_culling_shader(3) Manual Page

#extension GL_HUAWEI_cluster_culling_shader: enable

#define GPU_WARP_SIZE                   32
#define GPU_GROUP_SIZE                  GPU_WARP_SIZE

#define GPU_CLUSTER_PER_INVOCATION      1
#define GPU_CLUSTER_PER_WORKGROUP       (GPU_GROUP_SIZE * GPU_CLUSTER_PER_INVOCATION)

// Number of threads per workgroup
// - 1D only
// - warpsize = 32
layout(local_size_x=GPU_GROUP_SIZE, local_size_y=1, local_size_z=1) in;

#define GPU_DRAW_BUFFER_BINDING             0
#define GPU_INSTANCE_DESCRIPTOR_BINDING     1

struct BoundingSphere
{
  vec3 center;
  float radius;
};

struct InstanceData
{
  mat4 mvp_matrix;                      // mvp matrix.
  vec4 frustum_planes[6];               // six frustum planes
  mat4 model_matrix_transpose_inverse;  // inverse transpose of model matrix.
  vec3 view_origin;                     // view original
};

struct InstanceDescriptor
{
  uint begin;
  uint end;
  uint cluster_count;
  uint debug;
  BoundingSphere sphere;
  InstanceData instance_data;
};

struct DrawElementsCommand{
  uint indexcount;
  uint instanceCount;
  uint firstIndex;
  int  vertexoffset;
  uint firstInstance;
  uint cluster_id;
};

// indexed mode
out gl_PerClusterHUAWEI{
  uint gl_IndexCountHUAWEI;
  uint gl_InstanceCountHUAWEI;
  uint gl_FirstIndexHUAWEI;
  int  gl_VertexOffsetHUAWEI;
  uint gl_FirstInstanceHUAWEI;
  uint gl_ClusterIDHUAWEI;
  uint gl_ClusterShadingRateHUAWEI;
};

layout(binding = GPU_DRAW_BUFFER_BINDING, std430) buffer draw_indirect_ssbo
{
        DrawElementsCommand draw_commands[];
};

layout(binding = GPU_INSTANCE_DESCRIPTOR_BINDING, std430) buffer instance_descriptor_ssbo
{
        InstanceDescriptor instance_descriptors[];
};


float Distance(uint instance_id)
{
    vec3 v = normalize(instance_descriptor[instance_id].sphere.center -
                     instance_descriptor[instance_id].instance_data.view_origin);
    float dist = sqrt(dot(v,v));

    return dist;
}

bool isSphereOutsideFrustum( vec3 sphere_center, float sphere_radius )
{
  bool isInside = false;

  for(int i = 0; i < 6; i++)
  {
      isInside = isInside ||
      (dot(instance_descriptors[instance_id].instance_data.frustum_planes[i].xyz,
      sphere_center) + instance_descriptors[instance_id].instance_data.frustum_planes[i].w <
      sphere_radius);
  }
  return isInside;
}


void main()
{
    // get instance description
    instance_id = gl_GlobalInvocationID.x;
    InstanceDescriptor inst_desc = instance_descriptors[instance_id];

    //instance based culling
    bool render = !isSphereOutsideFrustum(inst_desc.sphere.center, inst_desc.sphere.radius);

    if (render)
    {
        // calculate distance
        float distance = Distance(instance_id);

        // update shading rate built-in variable
        if(distance > 0.7)
            gl_ClusterShadingRateHUAWEI =
                gl_ShadingRateFlag4VerticalPixelsEXT | gl_ShadingRateFlag4HorizontalPixelsEXT;
        else if(distance > 0.3)
            gl_ClusterShadingRateHUAWEI =
                gl_ShadingRateFlag2VerticalPixelsEXT | gl_ShadingRateFlag2HorizontalPixelsEXT;
        else
            gl_ClusterShadingRateHUAWEI = 0;

        // this is a visible cluster, update built-in output variable.
        // in case of indexed mode:
        gl_IndexCountHUAWEI     = draw_commands[cluster_id].indexcount;
        gl_InstanceCountHUAWEI  = draw_commands[cluster_id].instanceCount;
        gl_FirstIndexHUAWEI     = draw_commands[cluster_id].firstIndex;
        gl_VertexOffsetHUAWEI   = draw_commands[cluster_id].vertexoffset;
        gl_FirstInstanceHUAWEI  = draw_commands[cluster_id].firstInstance;
        gl_ClusterIDHUAWEI      = draw_commands[cluster_id].cluster_id;

        // emit built-in output variables as a drawing command to subsequent
        // rendering pipeline.
        dispatchClusterHUAWEI();
    }
}

// create a cluster culling shader stage info structure.
VkPipelineShaderStageCreateInfo ccsStageInfo{};
ccsStageInfo.sType = VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_CREATE_INFO;
ccsStageInfo.stage = VK_SHADER_STAGE_CLUSTER_CULLING_BIT_HUAWEI;
ccsStageInfo.module = clustercullingshaderModule;
ccsStageInfo.pName =  "main";

// pipeline shader stage creation
VkPipelineShaderStageCreateInfo shaderStages[] = { ccsStageInfo, vertexShaderStageInfo, fragmentShaderStageInfo };

// create graphics pipeline
VkGraphicsPipelineCreateInfo pipelineInfo{};
pipelineInfo.sType = VK_STRUCTURE_TYPE_GRAPHICS_PIPELINE_CREATE_INFO;
pipelineInfo.stageCount = 3;
pipelineInfo.pStage = shaderStages;
pipelineInfo.pVertexInputState = &vertexInputInfo;
// ...
VkPipeline graphicsPipeline;
VkCreateGraphicsPipelines(device, VK_NULL_HANDLE, 1, &pipelineInfo, nullptr, &graphicsPipeline);

vkCmdBindPipeline(commandBuffer, VK_PIPELINE_BIND_POINT_GRAPHICS, graphicsPipeline);
vkCmdDrawClusterHUAWEI(commandBuffer, groupCountX, 1, 1);
vkCmdEndRenderPass(commandBuffer);