1 files changed, 121 insertions, 0 deletions
diff --git a/src/crepe/system/ParticleSystem.cpp b/src/crepe/system/ParticleSystem.cpp
new file mode 100644
index 0000000..bbc7366
--- /dev/null
+++ b/src/crepe/system/ParticleSystem.cpp
@@ -0,0 +1,121 @@
+#include <chrono>
+#include <cmath>
+#include <cstdlib>
+#include <ctime>
+
+#include "../api/ParticleEmitter.h"
+#include "../api/Transform.h"
+#include "../manager/ComponentManager.h"
+#include "../manager/LoopTimerManager.h"
+
+#include "ParticleSystem.h"
+
+using namespace crepe;
+
+void ParticleSystem::fixed_update() {
+	// Get all emitters
+	const Mediator & mediator = this->mediator;
+	LoopTimerManager & loop_timer = mediator.loop_timer;
+	ComponentManager & mgr = mediator.component_manager;
+	float dt = loop_timer.get_scaled_fixed_delta_time().count();
+
+	RefVector<ParticleEmitter> emitters = mgr.get_components_by_type<ParticleEmitter>();
+
+	for (ParticleEmitter & emitter : emitters) {
+		// Get transform linked to emitter
+		const Transform & transform
+			= mgr.get_components_by_id<Transform>(emitter.game_object_id).front().get();
+
+		// Emit particles based on emission_rate
+		emitter.spawn_accumulator += emitter.data.emission_rate * dt;
+		while (emitter.spawn_accumulator >= 1.0) {
+			this->emit_particle(emitter, transform);
+			emitter.spawn_accumulator -= 1.0;
+		}
+
+		// Update all particles
+		for (Particle & particle : emitter.particles) {
+			if (particle.active) {
+				particle.update(dt);
+			}
+		}
+
+		// Check if within boundary
+		this->check_bounds(emitter, transform);
+	}
+}
+
+void ParticleSystem::emit_particle(ParticleEmitter & emitter, const Transform & transform) {
+	constexpr float DEG_TO_RAD = M_PI / 180.0;
+
+	vec2 initial_position = emitter.data.offset + transform.position;
+	float random_angle
+		= this->generate_random_angle(emitter.data.min_angle, emitter.data.max_angle);
+
+	float random_speed
+		= this->generate_random_speed(emitter.data.min_speed, emitter.data.max_speed);
+	float angle_radians = random_angle * DEG_TO_RAD;
+
+	vec2 velocity
+		= {random_speed * std::cos(angle_radians), random_speed * std::sin(angle_radians)};
+
+	for (Particle & particle : emitter.particles) {
+		if (!particle.active) {
+			particle.reset(emitter.data.end_lifespan, initial_position, velocity,
+						   random_angle);
+			break;
+		}
+	}
+}
+
+void ParticleSystem::check_bounds(ParticleEmitter & emitter, const Transform & transform) {
+	vec2 offset = emitter.data.boundary.offset + transform.position + emitter.data.offset;
+	float half_width = emitter.data.boundary.width / 2.0;
+	float half_height = emitter.data.boundary.height / 2.0;
+
+	float left = offset.x - half_width;
+	float right = offset.x + half_width;
+	float top = offset.y - half_height;
+	float bottom = offset.y + half_height;
+
+	for (Particle & particle : emitter.particles) {
+		const vec2 & position = particle.position;
+		bool within_bounds = (position.x >= left && position.x <= right && position.y >= top
+							  && position.y <= bottom);
+		//if not within bounds do a reset or stop velocity
+		if (!within_bounds) {
+			if (emitter.data.boundary.reset_on_exit) {
+				particle.active = false;
+			} else {
+				particle.velocity = {0, 0};
+				if (position.x < left) particle.position.x = left;
+				else if (position.x > right) particle.position.x = right;
+				if (position.y < top) particle.position.y = top;
+				else if (position.y > bottom) particle.position.y = bottom;
+			}
+		}
+	}
+}
+
+float ParticleSystem::generate_random_angle(float min_angle, float max_angle) const {
+	if (min_angle == max_angle) {
+		return min_angle;
+	} else if (min_angle < max_angle) {
+		return min_angle
+			   + static_cast<float>(std::rand() % static_cast<int>(max_angle - min_angle));
+	} else {
+		float angle_offset = (360 - min_angle) + max_angle;
+		float random_angle
+			= min_angle + static_cast<float>(std::rand() % static_cast<int>(angle_offset));
+		return (random_angle >= 360) ? random_angle - 360 : random_angle;
+	}
+}
+
+float ParticleSystem::generate_random_speed(float min_speed, float max_speed) const {
+	if (min_speed == max_speed) {
+		return min_speed;
+	} else {
+		return min_speed
+			   + static_cast<float>(std::rand() % static_cast<int>(max_speed - min_speed));
+	}
+}