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Build view-space light cluster grid in a compute pass

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Hirek
2026-10-15 14:16:55 +02:00
parent c0f45184b8
commit f85cf5fe52
11 changed files with 488 additions and 0 deletions
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66
gl/cluster_grid.cpp Normal file
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#include "stdafx.h"
#include "cluster_grid.h"
#include <cstring>
gl::cluster_grid::cluster_grid()
: m_aabbs(sizeof(cluster_aabb) * CLUSTER_COUNT, CLUSTER_AABB_SSBO_BINDING)
, m_ranges(sizeof(cluster_range) * CLUSTER_COUNT, CLUSTER_RANGE_SSBO_BINDING)
, m_indices(sizeof(uint32_t) * CLUSTER_COUNT * MAX_LIGHTS_PER_CLUSTER, CLUSTER_INDEX_SSBO_BINDING)
, m_counters(sizeof(cluster_counters), CLUSTER_COUNTER_SSBO_BINDING)
, m_params_buffer(sizeof(cluster_ubs), CLUSTER_UBO_BINDING)
{
// no light is assigned to any cluster until the culling pass runs
std::vector<uint8_t> const empty(sizeof(cluster_range) * CLUSTER_COUNT, 0);
m_ranges.update(empty.data(), 0, static_cast<GLsizeiptr>(empty.size()));
m_counters.update(cluster_counters{});
m_params_buffer.update(m_params);
}
void gl::cluster_grid::bind()
{
m_aabbs.bind_base();
m_ranges.bind_base();
m_indices.bind_base();
m_counters.bind_base();
m_params_buffer.bind_uniform();
}
bool gl::cluster_grid::update(const glm::mat4 &projection, float znear, float zfar, glm::vec2 viewport_size)
{
cluster_ubs params = m_params;
params.viewport_width = viewport_size.x;
params.viewport_height = viewport_size.y;
// clip space w is a function of the position in a perspective projection, and a constant in an orthographic one
bool const perspective{glm::length(glm::vec3{projection[0][3], projection[1][3], projection[2][3]}) > 1e-4f};
bool const usable{perspective && znear > 0.f && zfar > znear};
params.valid = usable ? 1 : 0;
if (usable && (projection != m_params.projection || znear != m_params.znear || zfar != m_params.zfar))
{
params.projection = projection;
params.znear = znear;
params.zfar = zfar;
params.slice_scale = static_cast<float>(CLUSTER_GRID_Z) / std::log(zfar / znear);
params.slice_bias = -std::log(znear) * params.slice_scale;
m_boxes_stale = true;
}
if (std::memcmp(&params, &m_params, sizeof(params)) != 0)
{
m_params = params;
m_params_buffer.update(m_params);
}
return usable && m_boxes_stale;
}
void gl::cluster_grid::build(program &build_program)
{
bind();
build_program.dispatch((CLUSTER_COUNT + CLUSTER_BUILD_GROUP_SIZE - 1) / CLUSTER_BUILD_GROUP_SIZE);
// the boxes are read by compute passes which follow, from the same shader storage buffer
memory_barrier(GL_SHADER_STORAGE_BARRIER_BIT);
m_boxes_stale = false;
}