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102 lines
3.6 KiB
C++
102 lines
3.6 KiB
C++
#pragma once
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#include <array>
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#include <memory>
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#include <optional>
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#include <glm/glm.hpp>
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#include "fence.h"
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#include "ssbo.h"
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#include "ubo.h"
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#include "shader.h"
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namespace gl
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{
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// GPU resources of the light cluster grid of one viewport. the grid cuts the view frustum of a pass into
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// CLUSTER_GRID_X x CLUSTER_GRID_Y screen tiles and CLUSTER_GRID_Z slices of depth, spaced exponentially
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// between znear and zfar (layout and binding points: ubo.h). depth is the clip space w of a point, which is
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// also 1.0 / gl_FragCoord.w of its fragment and, unlike the view space z, is right for tilted screens.
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// the buffers have a fixed size, so the grid survives changes of the resolution, fov and draw range: those
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// only make its parameters and boxes be recomputed.
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// bindings of the buffers are context state and the buffers are per viewport, so bind() has to be done in
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// the context and before every pass which uses the grid
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class cluster_grid
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{
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public:
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// what the culling pass reports about a frame
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struct cull_stats
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{
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// entries of the shared index list in use
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uint32_t index_count = 0;
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// (cluster, light) pairs dropped because the cluster was full
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uint32_t overflow_count = 0;
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// highest overflow_count seen since the grid was created
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uint32_t overflow_peak = 0;
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};
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cluster_grid();
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~cluster_grid();
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cluster_grid(const cluster_grid &) = delete;
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cluster_grid &operator=(const cluster_grid &) = delete;
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void bind();
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// refreshes the parameters for a pass: its projection, depth range and the size of the render target.
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// returns true if the boxes of the clusters no longer match them and build() has to run
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bool update(const glm::mat4 &projection, float znear, float zfar, glm::vec2 viewport_size);
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// recomputes the boxes of the clusters in view space with the program made from cluster_build.comp.
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// binds the grid, and leaves the boxes ready to be read by the compute passes which follow
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void build(program &build_program);
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// assigns the lights of light_ssbo to the clusters with the program made from cluster_cull.comp: zeroes the
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// counters, fills the (offset, count) of every cluster and the index list, and leaves them ready to be
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// read by the shading and the debug view which follow. the boxes have to be current (update(), build()) and the
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// grid valid. also queues the counters for reading back, see stats()
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void cull(program &cull_program);
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// false if the last update found no grid possible for the pass (orthographic projection)
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bool valid() const
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{
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return m_params.valid != 0;
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}
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const cluster_ubs ¶ms() const
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{
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return m_params;
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}
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// counters of the most recent culling pass whose result has reached the cpu, which takes a few frames
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// (read back without waiting for the gpu); empty until there is one
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std::optional<cull_stats> stats() const
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{
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return m_stats;
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}
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private:
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// cluster_aabb per cluster
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ssbo m_aabbs;
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// cluster_range per cluster
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ssbo m_ranges;
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// light indices of all clusters, allocated from m_counters.index_count
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ssbo m_indices;
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// cluster_counters
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ssbo m_counters;
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ubo m_params_buffer;
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cluster_ubs m_params{};
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bool m_boxes_stale = true;
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// counters copied for reading back: a queue of buffers, each with the fence of the copy into it
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static constexpr size_t READBACK_SLOTS = 4;
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struct readback_slot
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{
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GLuint buffer = 0;
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std::unique_ptr<fence> copied;
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};
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void collect_stats();
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std::array<readback_slot, READBACK_SLOTS> m_readback;
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// oldest slot in use and the number of slots in use
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size_t m_readback_first = 0;
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size_t m_readback_used = 0;
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std::optional<cull_stats> m_stats;
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};
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} // namespace gl
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