From 2c12446be8ee18e597a8c9b5d3bb018cbb11faa8 Mon Sep 17 00:00:00 2001
From: Daniel Bross <daniel@brossferatu.com>
Date: Fri, 11 Oct 2024 22:25:43 +0200
Subject: [PATCH] Particles file added

---
 core/particles.jai | 160 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 160 insertions(+)
 create mode 100644 core/particles.jai

diff --git a/core/particles.jai b/core/particles.jai
new file mode 100644
index 0000000..8c80c21
--- /dev/null
+++ b/core/particles.jai
@@ -0,0 +1,160 @@
+MAX_PARTICLES :: 2048;
+
+Particle :: struct {
+    velocity: Vector3;
+    position: Vector3;
+    color: Vector4;
+
+    initial_lifetime: float;
+    lifetime: float;
+
+    initial_size: float;
+    size: float;
+}
+
+Particle_Vertex :: struct {
+    position: Vector3;
+    color: Vector4;
+    uv: Vector2;
+}
+
+Particle_System :: struct {
+    active: bool;
+    particles: [..] Particle;
+    pipeline: Pipeline_State_Handle;
+
+    owning_entity: *Entity;
+
+    time: float;
+    position: Vector3;
+
+    vertex_buffer: Buffer_Handle;
+    
+    _locator: Bucket_Locator;
+
+    on_particle_update: (*Particle_System, float);
+}
+
+create_particle_system :: (pipeline: Pipeline_State_Handle, update_func: (*Particle_System, float), owning_entity: *Entity = null, scene: *Scene = null) -> *Particle_System {
+    lvl := ifx scene == null then game_state.current_scene else scene;
+    particle_system, locator := find_and_occupy_empty_slot(*scene.particle_systems);
+    particle_system._locator = locator;
+    particle_system.vertex_buffer = create_vertex_buffer(renderer, null, size_of(Particle_Vertex) * MAX_PARTICLES, stride=size_of(Particle_Vertex), mappable=true);
+    particle_system.pipeline = pipeline;
+    particle_system.on_particle_update = update_func;
+    particle_system.owning_entity = owning_entity;
+    return particle_system;
+}
+
+spawn_particle :: (system: *Particle_System, position: Vector3, velocity: Vector3 = .{0,0,0}, size: float = 1.0, lifetime: float = 1.0, color: Vector4 = .{1,1,1,1}) {
+    particle: Particle;
+    particle.position = position;
+    particle.velocity = velocity;
+    particle.size = size;
+    particle.initial_size = size;
+    particle.lifetime = lifetime;
+    particle.initial_lifetime = lifetime;
+    particle.color = color;
+
+    array_add(*system.particles, particle);
+}
+
+update_particle_systems :: (dt: float) {
+    for *system: game_state.current_scene.particle_systems {
+        if system.on_particle_update != null {
+            system.on_particle_update(system, dt);
+        }
+    }
+}
+
+update_particle_system :: (system: *Particle_System, dt: float) {
+}
+
+prepare_particle_system_for_rendering :: (system: Particle_System) {
+    up := game_state.camera.up;
+    right := game_state.camera.right;
+    forward := game_state.camera.forward;
+
+    rendering_data : [..] Particle_Vertex;
+    rendering_data.allocator = temp;
+
+    for p: system.particles {
+        //alpha := sin((p.lifetime / p.max_lifetime) * PI);
+        //color.w = alpha;
+        //size := p.size * alpha;
+
+        size := p.size;
+        color := p.color;
+        position := p.position - forward * (cast(float)it_index) * 0.01;
+        
+        // Tri 0
+        {
+            v : Particle_Vertex;
+            v.uv = .{1, 1};
+            v.position = position + up * size + right * size;
+            v.color = color;
+            array_add(*rendering_data, v);
+        }
+        {
+            v : Particle_Vertex;
+            v.uv = .{1, 0};
+            v.position = position - up * size + right * size;
+            v.color = color;
+            array_add(*rendering_data, v);
+        }
+        {
+            v : Particle_Vertex;
+            v.uv = .{0, 0};
+            v.position = position - up * size - right * size;
+            v.color = color;
+            array_add(*rendering_data, v);
+        }
+
+        // Tri 1
+        {
+            v : Particle_Vertex;
+            v.uv = .{0, 0};
+            v.position = position - up * size - right * size;
+            v.color = color;
+            array_add(*rendering_data, v);
+        }
+        {
+            v : Particle_Vertex;
+            v.uv = .{1, 0};
+            v.position = position + up * size - right * size;
+            v.color = color;
+            array_add(*rendering_data, v);
+        }
+        {
+            v : Particle_Vertex;
+            v.uv = .{1, 1};
+            v.position = position + up * size + right * size;
+            v.color = color;
+            array_add(*rendering_data, v);
+        }
+    }
+    
+    if rendering_data.count > 0 {
+        upload_data_to_buffer(renderer, system.vertex_buffer, rendering_data.data, size_of(Particle_Vertex) * rendering_data.count);
+    }
+}
+
+render_particle_systems :: () {
+    for system: game_state.current_scene.particle_systems {
+        prepare_particle_system_for_rendering(system);
+
+        if system.particles.count > 0 {
+            push_cmd_set_draw_mode(renderer, .FILL);
+            push_cmd_set_depth_write(renderer, true);
+            push_cmd_set_cull_face(renderer, .BACK);
+            push_cmd_set_pipeline_state(renderer, system.pipeline);
+
+            push_cmd_set_constant_buffer(renderer, 0, camera_buffer, .VERTEX);
+
+            push_cmd_set_vertex_buffer(renderer, system.vertex_buffer);
+
+            push_cmd_draw(renderer, system.particles.count * 6);
+        }
+    }
+}
+