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/*  godot_step_3d.cpp                                                     */
/**************************************************************************/
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#include "godot_step_3d.h"

#include "godot_constraint_3d.h"

#include "core/object/worker_thread_pool.h"
#include "core/os/os.h"

#define BODY_ISLAND_COUNT_RESERVE 128
#define BODY_ISLAND_SIZE_RESERVE 512
#define ISLAND_COUNT_RESERVE 128
#define ISLAND_SIZE_RESERVE 512
#define CONSTRAINT_COUNT_RESERVE 1024

void GodotStep3D::_populate_island(GodotBody3D *p_body, LocalVector<GodotBody3D *> &p_body_island, LocalVector<GodotConstraint3D *> &p_constraint_island) {
	p_body->set_island_step(_step);

	if (p_body->get_mode() > PhysicsServer3D::BODY_MODE_KINEMATIC) {
		// Only rigid bodies are tested for activation.
		p_body_island.push_back(p_body);
	}

	for (const KeyValue<GodotConstraint3D *, int> &E : p_body->get_constraint_map()) {
		GodotConstraint3D *constraint = E.key;
		if (constraint->get_island_step() == _step) {
			continue; // Already processed.
		}
		constraint->set_island_step(_step);
		p_constraint_island.push_back(constraint);

		all_constraints.push_back(constraint);

		// Find connected rigid bodies.
		for (int i = 0; i < constraint->get_body_count(); i++) {
			if (i == E.value) {
				continue;
			}
			GodotBody3D *other_body = constraint->get_body_ptr()[i];
			if (other_body->get_island_step() == _step) {
				continue; // Already processed.
			}
			if (other_body->get_mode() == PhysicsServer3D::BODY_MODE_STATIC) {
				continue; // Static bodies don't connect islands.
			}
			_populate_island(other_body, p_body_island, p_constraint_island);
		}

		// Find connected soft bodies.
		for (int i = 0; i < constraint->get_soft_body_count(); i++) {
			GodotSoftBody3D *soft_body = constraint->get_soft_body_ptr(i);
			if (soft_body->get_island_step() == _step) {
				continue; // Already processed.
			}
			_populate_island_soft_body(soft_body, p_body_island, p_constraint_island);
		}
	}
}

void GodotStep3D::_populate_island_soft_body(GodotSoftBody3D *p_soft_body, LocalVector<GodotBody3D *> &p_body_island, LocalVector<GodotConstraint3D *> &p_constraint_island) {
	p_soft_body->set_island_step(_step);

	for (GodotConstraint3D *E : p_soft_body->get_constraints()) {
		GodotConstraint3D *constraint = E;
		if (constraint->get_island_step() == _step) {
			continue; // Already processed.
		}
		constraint->set_island_step(_step);
		p_constraint_island.push_back(constraint);

		all_constraints.push_back(constraint);

		// Find connected rigid bodies.
		for (int i = 0; i < constraint->get_body_count(); i++) {
			GodotBody3D *body = constraint->get_body_ptr()[i];
			if (body->get_island_step() == _step) {
				continue; // Already processed.
			}
			if (body->get_mode() == PhysicsServer3D::BODY_MODE_STATIC) {
				continue; // Static bodies don't connect islands.
			}
			_populate_island(body, p_body_island, p_constraint_island);
		}
	}
}

void GodotStep3D::_setup_constraint(uint32_t p_constraint_index, void *p_userdata) {
	GodotConstraint3D *constraint = all_constraints[p_constraint_index];
	constraint->setup(delta);
}

void GodotStep3D::_pre_solve_island(LocalVector<GodotConstraint3D *> &p_constraint_island) const {
	uint32_t constraint_count = p_constraint_island.size();
	uint32_t valid_constraint_count = 0;
	for (uint32_t constraint_index = 0; constraint_index < constraint_count; ++constraint_index) {
		GodotConstraint3D *constraint = p_constraint_island[constraint_index];
		if (p_constraint_island[constraint_index]->pre_solve(delta)) {
			// Keep this constraint for solving.
			p_constraint_island[valid_constraint_count++] = constraint;
		}
	}
	p_constraint_island.resize(valid_constraint_count);
}

void GodotStep3D::_solve_island(uint32_t p_island_index, void *p_userdata) {
	LocalVector<GodotConstraint3D *> &constraint_island = constraint_islands[p_island_index];

	int current_priority = 1;

	uint32_t constraint_count = constraint_island.size();
	while (constraint_count > 0) {
		for (int i = 0; i < iterations; i++) {
			// Go through all iterations.
			for (uint32_t constraint_index = 0; constraint_index < constraint_count; ++constraint_index) {
				constraint_island[constraint_index]->solve(delta);
			}
		}

		// Check priority to keep only higher priority constraints.
		uint32_t priority_constraint_count = 0;
		++current_priority;
		for (uint32_t constraint_index = 0; constraint_index < constraint_count; ++constraint_index) {
			GodotConstraint3D *constraint = constraint_island[constraint_index];
			if (constraint->get_priority() >= current_priority) {
				// Keep this constraint for the next iteration.
				constraint_island[priority_constraint_count++] = constraint;
			}
		}
		constraint_count = priority_constraint_count;
	}
}

void GodotStep3D::_check_suspend(const LocalVector<GodotBody3D *> &p_body_island) const {
	bool can_sleep = true;

	uint32_t body_count = p_body_island.size();
	for (uint32_t body_index = 0; body_index < body_count; ++body_index) {
		GodotBody3D *body = p_body_island[body_index];

		if (!body->sleep_test(delta)) {
			can_sleep = false;
		}
	}

	// Put all to sleep or wake up everyone.
	for (uint32_t body_index = 0; body_index < body_count; ++body_index) {
		GodotBody3D *body = p_body_island[body_index];

		bool active = body->is_active();

		if (active == can_sleep) {
			body->set_active(!can_sleep);
		}
	}
}

void GodotStep3D::step(GodotSpace3D *p_space, real_t p_delta) {
	p_space->lock(); // can't access space during this

	p_space->setup(); //update inertias, etc

	p_space->set_last_step(p_delta);

	iterations = p_space->get_solver_iterations();
	delta = p_delta;

	const SelfList<GodotBody3D>::List *body_list = &p_space->get_active_body_list();

	const SelfList<GodotSoftBody3D>::List *soft_body_list = &p_space->get_active_soft_body_list();

	/* INTEGRATE FORCES */

	uint64_t profile_begtime = OS::get_singleton()->get_ticks_usec();
	uint64_t profile_endtime = 0;

	int active_count = 0;

	const SelfList<GodotBody3D> *b = body_list->first();
	while (b) {
		b->self()->integrate_forces(p_delta);
		b = b->next();
		active_count++;
	}

	/* UPDATE SOFT BODY MOTION */

	const SelfList<GodotSoftBody3D> *sb = soft_body_list->first();
	while (sb) {
		sb->self()->predict_motion(p_delta);
		sb = sb->next();
		active_count++;
	}

	p_space->set_active_objects(active_count);

	// Update the broadphase to register collision pairs.
	p_space->update();

	{ //profile
		profile_endtime = OS::get_singleton()->get_ticks_usec();
		p_space->set_elapsed_time(GodotSpace3D::ELAPSED_TIME_INTEGRATE_FORCES, profile_endtime - profile_begtime);
		profile_begtime = profile_endtime;
	}

	/* GENERATE CONSTRAINT ISLANDS FOR MOVING AREAS */

	uint32_t island_count = 0;

	const SelfList<GodotArea3D>::List &aml = p_space->get_moved_area_list();

	while (aml.first()) {
		for (GodotConstraint3D *E : aml.first()->self()->get_constraints()) {
			GodotConstraint3D *constraint = E;
			if (constraint->get_island_step() == _step) {
				continue;
			}
			constraint->set_island_step(_step);

			// Each constraint can be on a separate island for areas as there's no solving phase.
			++island_count;
			if (constraint_islands.size() < island_count) {
				constraint_islands.resize(island_count);
			}
			LocalVector<GodotConstraint3D *> &constraint_island = constraint_islands[island_count - 1];
			constraint_island.clear();

			all_constraints.push_back(constraint);
			constraint_island.push_back(constraint);
		}
		p_space->area_remove_from_moved_list((SelfList<GodotArea3D> *)aml.first()); //faster to remove here
	}

	/* GENERATE CONSTRAINT ISLANDS FOR ACTIVE RIGID BODIES */

	b = body_list->first();

	uint32_t body_island_count = 0;

	while (b) {
		GodotBody3D *body = b->self();

		if (body->get_island_step() != _step) {
			++body_island_count;
			if (body_islands.size() < body_island_count) {
				body_islands.resize(body_island_count);
			}
			LocalVector<GodotBody3D *> &body_island = body_islands[body_island_count - 1];
			body_island.clear();
			body_island.reserve(BODY_ISLAND_SIZE_RESERVE);

			++island_count;
			if (constraint_islands.size() < island_count) {
				constraint_islands.resize(island_count);
			}
			LocalVector<GodotConstraint3D *> &constraint_island = constraint_islands[island_count - 1];
			constraint_island.clear();
			constraint_island.reserve(ISLAND_SIZE_RESERVE);

			_populate_island(body, body_island, constraint_island);

			if (body_island.is_empty()) {
				--body_island_count;
			}

			if (constraint_island.is_empty()) {
				--island_count;
			}
		}
		b = b->next();
	}

	/* GENERATE CONSTRAINT ISLANDS FOR ACTIVE SOFT BODIES */

	sb = soft_body_list->first();
	while (sb) {
		GodotSoftBody3D *soft_body = sb->self();

		if (soft_body->get_island_step() != _step) {
			++body_island_count;
			if (body_islands.size() < body_island_count) {
				body_islands.resize(body_island_count);
			}
			LocalVector<GodotBody3D *> &body_island = body_islands[body_island_count - 1];
			body_island.clear();
			body_island.reserve(BODY_ISLAND_SIZE_RESERVE);

			++island_count;
			if (constraint_islands.size() < island_count) {
				constraint_islands.resize(island_count);
			}
			LocalVector<GodotConstraint3D *> &constraint_island = constraint_islands[island_count - 1];
			constraint_island.clear();
			constraint_island.reserve(ISLAND_SIZE_RESERVE);

			_populate_island_soft_body(soft_body, body_island, constraint_island);

			if (body_island.is_empty()) {
				--body_island_count;
			}

			if (constraint_island.is_empty()) {
				--island_count;
			}
		}
		sb = sb->next();
	}

	p_space->set_island_count((int)island_count);

	{ //profile
		profile_endtime = OS::get_singleton()->get_ticks_usec();
		p_space->set_elapsed_time(GodotSpace3D::ELAPSED_TIME_GENERATE_ISLANDS, profile_endtime - profile_begtime);
		profile_begtime = profile_endtime;
	}

	/* SETUP CONSTRAINTS / PROCESS COLLISIONS */

	uint32_t total_constraint_count = all_constraints.size();
	WorkerThreadPool::GroupID group_task = WorkerThreadPool::get_singleton()->add_template_group_task(this, &GodotStep3D::_setup_constraint, nullptr, total_constraint_count, -1, true, SNAME("Physics3DConstraintSetup"));
	WorkerThreadPool::get_singleton()->wait_for_group_task_completion(group_task);

	{ //profile
		profile_endtime = OS::get_singleton()->get_ticks_usec();
		p_space->set_elapsed_time(GodotSpace3D::ELAPSED_TIME_SETUP_CONSTRAINTS, profile_endtime - profile_begtime);
		profile_begtime = profile_endtime;
	}

	/* PRE-SOLVE CONSTRAINT ISLANDS */

	// WARNING: This doesn't run on threads, because it involves thread-unsafe processing.
	for (uint32_t island_index = 0; island_index < island_count; ++island_index) {
		_pre_solve_island(constraint_islands[island_index]);
	}

	/* SOLVE CONSTRAINT ISLANDS */

	// WARNING: `_solve_island` modifies the constraint islands for optimization purpose,
	// their content is not reliable after these calls and shouldn't be used anymore.
	group_task = WorkerThreadPool::get_singleton()->add_template_group_task(this, &GodotStep3D::_solve_island, nullptr, island_count, -1, true, SNAME("Physics3DConstraintSolveIslands"));
	WorkerThreadPool::get_singleton()->wait_for_group_task_completion(group_task);

	{ //profile
		profile_endtime = OS::get_singleton()->get_ticks_usec();
		p_space->set_elapsed_time(GodotSpace3D::ELAPSED_TIME_SOLVE_CONSTRAINTS, profile_endtime - profile_begtime);
		profile_begtime = profile_endtime;
	}

	/* INTEGRATE VELOCITIES */

	b = body_list->first();
	while (b) {
		const SelfList<GodotBody3D> *n = b->next();
		b->self()->integrate_velocities(p_delta);
		b = n;
	}

	/* SLEEP / WAKE UP ISLANDS */

	for (uint32_t island_index = 0; island_index < body_island_count; ++island_index) {
		_check_suspend(body_islands[island_index]);
	}

	/* UPDATE SOFT BODY CONSTRAINTS */

	sb = soft_body_list->first();
	while (sb) {
		sb->self()->solve_constraints(p_delta);
		sb = sb->next();
	}

	{ //profile
		profile_endtime = OS::get_singleton()->get_ticks_usec();
		p_space->set_elapsed_time(GodotSpace3D::ELAPSED_TIME_INTEGRATE_VELOCITIES, profile_endtime - profile_begtime);
		profile_begtime = profile_endtime;
	}

	all_constraints.clear();

	p_space->unlock();
	_step++;
}

GodotStep3D::GodotStep3D() {
	body_islands.reserve(BODY_ISLAND_COUNT_RESERVE);
	constraint_islands.reserve(ISLAND_COUNT_RESERVE);
	all_constraints.reserve(CONSTRAINT_COUNT_RESERVE);
}

GodotStep3D::~GodotStep3D() {
}
