godot/servers/visual/portals/portal_tracer.h

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/*  portal_tracer.h                                                      */
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#ifndef PORTAL_TRACER_H
#define PORTAL_TRACER_H

#include "core/bitfield_dynamic.h"
#include "core/local_vector.h"
#include "portal_occlusion_culler.h"
#include "portal_types.h"

#ifdef TOOLS_ENABLED
// use this for checking for instance lifetime errors, disable normally
//#define PORTAL_RENDERER_STORE_MOVING_RIDS
#endif

class PortalRenderer;
struct VSRoom;

class PortalTracer {
public:
	// a bitfield for which statics have been hit this time,
	// and a list of showing statics
	class TraceResult {
	public:
		void create(int p_num_statics) {
			bf_visible_statics.create(p_num_statics);
		}
		void clear() {
			bf_visible_statics.blank();
			visible_static_ids.clear();
			visible_roamer_pool_ids.clear();
		}

		BitFieldDynamic bf_visible_statics;
		LocalVector<uint32_t> visible_static_ids;
		LocalVector<uint32_t> visible_roamer_pool_ids;
	};

	struct TraceParams {
		bool use_pvs;
		uint8_t *decompressed_room_pvs;
	};

	// The recursive visibility function needs to allocate lists of planes each time a room is traversed.
	// Instead of doing this allocation on the fly we will use a pool which should be much faster and nearer
	// constant time.

	// Note this simple pool isn't super optimal but should be fine for now.
	class PlanesPool {
	public:
		// maximum number of vectors in the pool
		const static int POOL_MAX = 32;

		void reset();

		// request a new vector of planes .. returns the pool id, or -1 if pool is empty
		unsigned int request();

		// return pool id to the pool
		void free(unsigned int ui);

		LocalVector<Plane> &get(unsigned int ui) { return _planes[ui]; }

		PlanesPool();

	private:
		LocalVector<Plane> _planes[POOL_MAX];

		// list of pool ids that are free and can be allocated
		uint8_t _freelist[POOL_MAX];
		uint32_t _num_free;
	};

	// for debugging, instead of doing a normal trace, show the objects that are sprawled from the current room
	void trace_debug_sprawl(PortalRenderer &p_portal_renderer, const Vector3 &p_pos, int p_start_room_id, TraceResult &r_result);

	// trace statics, dynamics and roaming
	void trace(PortalRenderer &p_portal_renderer, const Vector3 &p_pos, const LocalVector<Plane> &p_planes, int p_start_room_id, TraceResult &r_result);

	// globals are handled separately as they don't care about the rooms
	int trace_globals(const LocalVector<Plane> &p_planes, VSInstance **p_result_array, int first_result, int p_result_max, uint32_t p_mask, bool p_override_camera);

	void set_depth_limit(int p_limit) { _depth_limit = p_limit; }
	int get_depth_limit() const { return _depth_limit; }

	// special function for occlusion culling only that does not use portals / rooms,
	// but allows using occluders with the main scene
	int occlusion_cull(PortalRenderer &p_portal_renderer, const Vector3 &p_point, const Vector<Plane> &p_convex, VSInstance **p_result_array, int p_num_results);

private:
	// main tracing function is recursive
	void trace_recursive(const TraceParams &p_params, int p_depth, int p_room_id, const LocalVector<Plane> &p_planes, int p_from_external_room_id = -1);

	// use pvs to cull instead of dynamically using portals
	// this is a faster trace but less accurate. Only possible if PVS has been generated.
	void trace_pvs(int p_source_room_id, const LocalVector<Plane> &p_planes);

	// debug version
	void trace_debug_sprawl_recursive(int p_depth, int p_room_id);

	void cull_statics(const VSRoom &p_room, const LocalVector<Plane> &p_planes);
	void cull_statics_debug_sprawl(const VSRoom &p_room);
	void cull_roamers(const VSRoom &p_room, const LocalVector<Plane> &p_planes);

	// if an aabb is in front of any of the culling planes, it can't be seen so returns false
	bool test_cull_inside(const AABB &p_aabb, const LocalVector<Plane> &p_planes, bool p_test_explicit_near_plane = true) const {
		for (unsigned int p = 0; p < p_planes.size(); p++) {
			real_t r_min, r_max;
			p_aabb.project_range_in_plane(p_planes[p], r_min, r_max);

			if (r_min > 0.0) {
				return false;
			}
		}

		if (p_test_explicit_near_plane) {
			real_t r_min, r_max;
			p_aabb.project_range_in_plane(_near_and_far_planes[0], r_min, r_max);

			if (r_min > 0.0) {
				return false;
			}
		}

		return true;
	}

	// local versions to prevent passing around the recursive functions
	PortalRenderer *_portal_renderer = nullptr;
	Vector3 _trace_start_point;
	TraceResult *_result = nullptr;
	Plane _near_and_far_planes[2];

	PlanesPool _planes_pool;
	int _depth_limit = 16;
	PortalOcclusionCuller _occlusion_culler;

	// keep a tick count for each trace, to avoid adding a visible
	// object to the hit list more than once per tick
	// (this makes more sense than bitfield for moving objects)
	uint32_t _tick = 0;
};

#endif