Add particles!

game/systems/s_animation.c

@@ -3,6 +3,109 @@
 #include "../game_state.h"
 
 #include <raymath.h>
+#include <stdlib.h>
+
+void updateParticleEmitter(ecs_iter_t *it) {
+    ParticleEmitter *emitter = ecs_field(it, ParticleEmitter, 1);
+    f32 dt = GetFrameTime();
+
+    for (i32 i = 0; i < it->count; i++) {
+        ecs_entity_t entity = it->entities[i];
+        if (ecs_has(ECS, entity, EmitterAttachment)) {
+            EmitterAttachment attachment = *ecs_get(ECS, entity, EmitterAttachment);
+            if (!ecs_is_alive(ECS, attachment.baseEntity)) {
+                ecs_delete(ECS, entity);
+                continue;
+            }
+            Vector2 pos = *ecs_get(ECS, entity, Position);
+            pos = Vector2Add(pos, attachment.offset);
+            emitter->pos = pos;
+        }
+
+        emitter[i].emitterElapsed += dt;
+        if (emitter[i].emitterElapsed >= emitter[i].emitterLifetime)
+            ecs_delete(ECS, entity);
+    }
+}
+
+static inline int lerpInt(int start, int end, int amount)
+{
+    float result = start + amount*(end - start);
+
+    return result;
+}
+bool updateParticle(const Texture2D tex, Particle *particle, f32 dt) {
+    f32 alpha = particle->elapsed / particle->lifetime;
+
+    Vector2 vel = Vector2Lerp(particle->startVel, particle->endVel, alpha);
+    f32 size = Lerp(particle->startSize, particle->endSize, alpha);
+    f32 rot = Lerp(particle->startRotSpeed, particle->endRotSpeed, alpha);
+    Color startC = particle->startColor;
+    Color endC = particle->endColor;
+    Color color = {
+            .r = lerpInt(startC.r, endC.r, alpha),
+            .g = lerpInt(startC.g, endC.g, alpha),
+            .b = lerpInt(startC.b, endC.b, alpha),
+            .a = lerpInt(startC.a, endC.a, alpha)
+    };
+
+    //BeginBlendMode(particle->blend);
+    f32 hSize = size * 0.5f;
+    Vector2 center = particle->pos;
+    Rectangle src = getTextureRect(particle->tileID);
+    src.x += 0.1f;
+    src.y += 0.1f;
+    src.width -= 0.2f;
+    src.height -= 0.2f;
+    DrawTexturePro(tex, src, (Rectangle) {
+            center.x,
+            center.y,
+            size, size
+    }, (Vector2) {hSize, hSize}, rot, color);
+    //EndBlendMode();
+
+    particle->pos = Vector2Add(particle->pos, Vector2Scale(vel, dt));
+    particle->elapsed += dt;
+    return alpha >= 1.0f;
+}
+// https://stackoverflow.com/questions/13408990/how-to-generate-random-float-number-in-c
+static inline f32 randFloatRange(f32 min, f32 max) {
+    float scale = rand() / (float) RAND_MAX; /* [0, 1.0] */
+    return min + scale * ( max - min );      /* [min, max] */
+}
+static inline Vector2 randVector2Range(Vector2 from, Vector2 to) {
+    return (Vector2) {
+            randFloatRange(from.x, to.x),
+            randFloatRange(from.y, to.y)
+    };
+}
+static inline Color randColorRange(Color from, Color to) {
+    return (Color) {
+            .r = GetRandomValue(from.r, to.r),
+            .g = GetRandomValue(from.g, to.g),
+            .b = GetRandomValue(from.b, to.b),
+            .a = GetRandomValue(from.a, to.a),
+    };
+}
+Particle spawnParticle(const ParticleEmitter *emitter) {
+    const struct ParticleEmitterData *data = &emitter->data;
+    return (Particle) {
+            .pos = Vector2Add(emitter->pos, randVector2Range(data->minOffset, data->maxOffset)),
+            .rotation = 0.0f,
+            .startVel = randVector2Range(data->minStartVel, data->maxStartVel),
+            .endVel = randVector2Range(data->minEndVel, data->maxEndVel),
+            .startSize = randFloatRange(data->minStartSize, data->maxStartSize),
+            .endSize = randFloatRange(data->minEndSize, data->maxEndSize),
+            .startRotSpeed = randFloatRange(data->minStartRotSpeed, data->maxStartRotSpeed),
+            .endRotSpeed = randFloatRange(data->minEndRotSpeed, data->maxEndRotSpeed),
+            .startColor = randColorRange(data->minStartColor, data->maxStartColor),
+            .endColor = randColorRange(data->minEndColor, data->maxEndColor),
+            .blend = data->blend,
+            .tileID = data->tileID,
+            .elapsed = 0.0f,
+            .lifetime = randFloatRange(data->minLifetime, data->maxLifetime),
+    };
+}
 
 void updateAnimationState(ecs_iter_t *it) {
     Animation *anim = ecs_field(it, Animation, 1);