work on particles

src/particles/particles.jai

@@ -0,0 +1,257 @@
+#scope_export
+
+g_pending_emitter_world_name : string;
+
+particles_process_deferred_loads :: () {
+    if g_pending_emitter_world_name.count == 0 then return;
+    name := g_pending_emitter_world_name;
+    g_pending_emitter_world_name = "";
+    load_emitters_for_world(name);
+    free(name.data);
+}
+
+Particle_Emitter_Definition :: struct {
+    name             : string;
+    sprite_sheet     : string;
+    emission_rate    : float = 10.0;
+    lifetime_min     : float = 0.5;
+    lifetime_max     : float = 2.0;
+    velocity         : Vector3;
+    velocity_spread  : Vector3;
+    size_start       : float = 0.5;
+    size_end         : float = 0.0;
+    color_start      : Vector4 = .{1, 1, 1, 1};
+    color_end        : Vector4 = .{1, 1, 1, 0};
+    frame_count      : int = 1;
+    gravity          : float = 2.0;
+
+    sprite_image     : sg_image; // resolved at runtime from sprite_sheet name
+}
+
+Particle_Emitter_Instance :: struct {
+    definition        : *Particle_Emitter_Definition;
+    definition_name   : string;
+    position          : Vector3;
+    active            : bool = true;
+    spawn_accumulator : float;
+}
+
+Particle :: struct {
+    position   : Vector3;
+    velocity   : Vector3;
+    age        : float;
+    lifetime   : float;
+    gravity    : float;
+    alive      : bool;
+    definition : *Particle_Emitter_Definition;
+}
+
+MAX_PARTICLES : s32 : 2048;
+
+g_particles          : [2048] Particle;
+g_emitter_instances  : [..] Particle_Emitter_Instance;
+g_emitter_defs       : [..] Particle_Emitter_Definition;
+
+tick_particles :: (dt: float) {
+    for *p: g_particles {
+        if !p.alive then continue;
+        p.age += dt;
+        if p.age >= p.lifetime {
+            p.alive = false;
+            continue;
+        }
+        p.velocity.y   -= p.gravity * dt;
+        p.position     += p.velocity * dt;
+    }
+
+    for *inst: g_emitter_instances {
+        if !inst.active then continue;
+        if inst.definition == null then continue;
+        def := inst.definition;
+        inst.spawn_accumulator += def.emission_rate * dt;
+        while inst.spawn_accumulator >= 1.0 {
+            inst.spawn_accumulator -= 1.0;
+            spawn_one_particle(inst.position, def);
+        }
+    }
+}
+
+add_particle_render_tasks :: () {
+    for *def: g_emitter_defs {
+        if def.sprite_image.id == 0 then continue;
+
+        instances : [..] Particle_Instance_Data;
+        instances.allocator = temp;
+
+        for *p: g_particles {
+            if !p.alive then continue;
+            if p.definition != def then continue;
+
+            t := p.age / p.lifetime;
+            t = clamp(t, 0.0, 1.0);
+
+            frame_count := cast(s32) max(def.frame_count, 1);
+            frame_idx   := cast(s32)(t * cast(float) frame_count);
+            frame_idx    = clamp(frame_idx, 0, frame_count - 1);
+
+            frame_w  := 1.0 / cast(float) frame_count;
+            uv_rect  := Vector4.{frame_idx * frame_w, 0.0, frame_w, 1.0};
+
+            size  := def.size_start + (def.size_end - def.size_start) * t;
+            color := lerp_color(def.color_start, def.color_end, t);
+
+            inst : Particle_Instance_Data;
+            inst.pos_size = .{p.position.x, p.position.y, p.position.z, size};
+            inst.uv_rect  = uv_rect;
+            inst.color    = color;
+            array_add(*instances, inst);
+        }
+
+        if instances.count == 0 then continue;
+
+        task : Rendering_Task_Particles;
+        task.instances    = instances;
+        task.sprite_image = def.sprite_image;
+        add_rendering_task(task);
+    }
+}
+
+clear_particle_emitter_instances :: () {
+    array_reset(*g_emitter_instances);
+    for *p: g_particles {
+        p.alive = false;
+    }
+}
+
+place_emitter :: (def_name: string, position: Vector3) {
+    inst : Particle_Emitter_Instance;
+    inst.definition_name = sprint("%", def_name);
+    inst.position        = position;
+    inst.active          = true;
+    resolve_emitter_definition(*inst);
+    array_add(*g_emitter_instances, inst);
+}
+
+remove_emitter_at_index :: (idx: int) {
+    if idx < 0 || idx >= g_emitter_instances.count then return;
+    array_unordered_remove_by_index(*g_emitter_instances, idx);
+}
+
+resolve_all_emitter_instances :: () {
+    for *inst: g_emitter_instances {
+        resolve_emitter_definition(inst);
+    }
+}
+
+get_emitter_def_names :: () -> []string {
+    names : [..] string;
+    names.allocator = temp;
+    for def: g_emitter_defs {
+        array_add(*names, def.name);
+    }
+    return names;
+}
+
+save_particle_definition :: (def: Particle_Emitter_Definition) {
+    #if OS != .WASM {
+        file :: #import "File";
+        dir := "./game/resources/particles";
+        file.make_directory_if_it_does_not_exist(dir, recursive = true);
+        path := tprint("%/%.emitter.json", dir, def.name);
+        json := Jaison.json_write_string(def,, temp);
+        file.write_entire_file(path, json);
+        log_info("Saved particle definition '%'", def.name);
+    }
+}
+
+load_emitters_for_world :: (world_name: string) {
+    #if OS != .WASM {
+        file :: #import "File";
+        path := tprint("./game/resources/worlds/%/emitters.json", world_name);
+        data, ok := file.read_entire_file(path);
+        if !ok then return;
+        defer free(data.data);
+
+        Emitter_Entry :: struct {
+            definition : string;
+            position   : [3] float;
+        }
+        success, entries := Jaison.json_parse_string(cast(string) data, [] Emitter_Entry,, temp);
+        if !success {
+            log_error("Failed to parse emitters.json for world '%'", world_name);
+            return;
+        }
+        for entry: entries {
+            pos := Vector3.{entry.position[0], entry.position[1], entry.position[2]};
+            place_emitter(entry.definition, pos);
+        }
+        log_info("Loaded % emitters for world '%'", entries.count, world_name);
+    }
+}
+
+save_emitters_for_world :: (world_name: string) {
+    #if OS != .WASM {
+        file :: #import "File";
+        dir := tprint("./game/resources/worlds/%", world_name);
+        file.make_directory_if_it_does_not_exist(dir, recursive = true);
+        path := tprint("%/emitters.json", dir);
+
+        Emitter_Entry :: struct {
+            definition : string;
+            position   : [3] float;
+        }
+        entries : [..] Emitter_Entry;
+        entries.allocator = temp;
+        for inst: g_emitter_instances {
+            e : Emitter_Entry;
+            e.definition   = inst.definition_name;
+            e.position[0]  = inst.position.x;
+            e.position[1]  = inst.position.y;
+            e.position[2]  = inst.position.z;
+            array_add(*entries, e);
+        }
+        json := Jaison.json_write_string(entries,, temp);
+        file.write_entire_file(path, json);
+        log_info("Saved % emitters for world '%'", entries.count, world_name);
+    }
+}
+
+#scope_file
+
+Random :: #import "Random";
+
+rng :: inline (lo: float, hi: float) -> float {
+    return lo + Random.random_get_zero_to_one() * (hi - lo);
+}
+
+spawn_one_particle :: (position: Vector3, def: *Particle_Emitter_Definition) {
+    for *p: g_particles {
+        if p.alive then continue;
+        p.alive    = true;
+        p.age      = 0;
+        p.lifetime = rng(def.lifetime_min, def.lifetime_max);
+        p.position = position;
+        p.velocity = def.velocity + Vector3.{
+            rng(-def.velocity_spread.x, def.velocity_spread.x),
+            rng(-def.velocity_spread.y, def.velocity_spread.y),
+            rng(-def.velocity_spread.z, def.velocity_spread.z),
+        };
+        p.gravity    = def.gravity;
+        p.definition = def;
+        return;
+    }
+}
+
+lerp_color :: (a: Vector4, b: Vector4, t: float) -> Vector4 {
+    return a * (1.0 - t) + b * t;
+}
+
+resolve_emitter_definition :: (inst: *Particle_Emitter_Instance) {
+    for *def: g_emitter_defs {
+        if def.name == inst.definition_name {
+            inst.definition = def;
+            return;
+        }
+    }
+    inst.definition = null;
+}