particle_task.hpp

// SPDX-License-Identifier: MIT
#ifndef LIBSBX_PARTICLES_PARTICLE_TASK_HPP_
#define LIBSBX_PARTICLES_PARTICLE_TASK_HPP_
 
#include <cstdint>
#include <filesystem>
#include <unordered_map>
 
#include <vulkan/vulkan.h>
 
#include <libsbx/memory/tracking_allocator.hpp>
 
#include <libsbx/core/engine.hpp>
 
#include <libsbx/graphics/task.hpp>
#include <libsbx/graphics/graphics_module.hpp>
#include <libsbx/graphics/commands/command_buffer.hpp>
 
#include <libsbx/graphics/buffers/storage_buffer.hpp>
#include <libsbx/graphics/buffers/push_handler.hpp>
 
#include <libsbx/graphics/descriptor/descriptor_handler.hpp>
 
#include <libsbx/graphics/pipeline/compute_pipeline.hpp>
 
#include <libsbx/scenes/scene.hpp>
 
#include <libsbx/particles/particle_emitter.hpp>
 
namespace sbx::particles {
 
class particle_task final : public graphics::task {
 
  inline static constexpr auto default_pipeline_path = std::string_view{"engine://shaders/particles"};
 
public:
 
  particle_task(const std::filesystem::path& path = default_pipeline_path);
 
  ~particle_task() override = default;
 
  auto execute(graphics::command_buffer& command_buffer) -> void override;
 
  auto remove_emitter(scenes::node node) -> void;
 
  [[nodiscard]] auto particle_buffer(scenes::node node) const -> graphics::storage_buffer_handle;
 
  [[nodiscard]] auto alive_list_buffer(scenes::node node) const -> graphics::storage_buffer_handle;
 
  [[nodiscard]] auto indirect_buffer(scenes::node node) const -> graphics::storage_buffer_handle;
 
private:
 
  struct alignas(16) emitter_params {
    math::color initial_color;
    math::color end_color;
    math::vector3 emitter_position;
    std::float_t delta_time;
    math::vector3 emission_shape_min;
    std::float_t emission_rate;
    math::vector3 emission_shape_max;
    std::float_t time;
    math::vector3 gravity;
    std::float_t drag;
    math::vector2 initial_speed;
    math::vector2 initial_lifetime;
    math::vector2 initial_size;
    math::vector2 initial_rotation;
    std::float_t end_size_scale;
    std::uint32_t max_particles;
    std::uint32_t emit_count;
    std::uint32_t random_seed;
    std::uint32_t texture_count;
    std::uint32_t _pad0;
    std::uint32_t _pad1;
    std::uint32_t _pad2;
  }; // struct emitter_params
 
  static_assert(alignof(emitter_params) == 16u);
  static_assert(sizeof(emitter_params) % 16u == 0u);
 
  struct emitter_gpu_data {
    // Buffers
    graphics::storage_buffer_handle particle_buffer;
    graphics::storage_buffer_handle counter_buffer;
    graphics::storage_buffer_handle alive_list_buffer;
    graphics::storage_buffer_handle indirect_buffer;
 
    // Descriptors
    graphics::descriptor_handler reset_descriptor;
    graphics::descriptor_handler clear_descriptor;
    graphics::descriptor_handler emit_descriptor;
    graphics::descriptor_handler simulate_descriptor;
    graphics::descriptor_handler prepare_indirect_descriptor;
 
    // State
    bool reset_requested{true};
 
    emitter_gpu_data(graphics::compute_pipeline& reset_pipeline, graphics::compute_pipeline& clear_pipeline, graphics::compute_pipeline& emit_pipeline, graphics::compute_pipeline& simulate_pipeline, graphics::compute_pipeline& prepare_indirect_pipeline)
    : reset_descriptor{reset_pipeline, 0u},
      clear_descriptor{clear_pipeline, 0u},
      emit_descriptor{emit_pipeline, 0u},
      simulate_descriptor{simulate_pipeline, 0u},
      prepare_indirect_descriptor{prepare_indirect_pipeline, 0u} { }
 
  }; // struct emitter_gpu_data
 
  auto _get_or_create_gpu_data(scenes::node node, const particle_emitter& emitter) -> emitter_gpu_data&;
 
  auto _initialize_buffers(emitter_gpu_data& gpu_data, const particle_emitter& emitter) -> void;
 
  auto _build_emitter_params(const particle_emitter& emitter, const math::vector3& position, std::uint32_t emit_count, std::float_t delta_time) -> emitter_params;
 
  auto _dispatch_reset(graphics::command_buffer& command_buffer, emitter_gpu_data& gpu_data) -> void;
 
  auto _dispatch_clear(graphics::command_buffer& command_buffer, emitter_gpu_data& gpu_data, const emitter_params& params) -> void;
 
  auto _dispatch_emit(graphics::command_buffer& command_buffer, emitter_gpu_data& gpu_data, const emitter_params& params) -> void;
 
  auto _dispatch_simulate(graphics::command_buffer& command_buffer, emitter_gpu_data& gpu_data, const emitter_params& params) -> void;
 
  auto _dispatch_prepare_indirect(graphics::command_buffer& command_buffer, emitter_gpu_data& gpu_data) -> void;
 
  static auto _barrier_compute_to_compute(graphics::command_buffer& command_buffer) -> void;
 
  static auto _barrier_compute_to_draw(graphics::command_buffer& command_buffer) -> void;
 
  // Pipelines
  graphics::compute_pipeline _reset_pipeline;
  graphics::compute_pipeline _clear_pipeline;
  graphics::compute_pipeline _emit_pipeline;
  graphics::compute_pipeline _simulate_pipeline;
  graphics::compute_pipeline _prepare_indirect_pipeline;
 
  // Push handlers
  graphics::push_handler _clear_push_handler;
  graphics::push_handler _emit_push_handler;
  graphics::push_handler _simulate_push_handler;
 
  // Per-emitter GPU data
  std::unordered_map<scenes::node, emitter_gpu_data> _emitter_gpu_data;
 
  std::uint32_t _frame_seed{0};
 
}; // class particle_task
 
} // namespace sbx::particles
 
#endif // LIBSBX_PARTICLES_PARTICLE_TASK_HPP_