kitchen: README + MISSIONS/engine-c keep-drop notes

engine-c/src/projectiles.c

@@ -0,0 +1,106 @@
+#include "kknd.h"
+
+/* =========================================================================
+ * projectiles.c - Bullets, missiles and particle effects.
+ * ========================================================================= */
+
+static RNG g_prng;
+static int g_prng_init = 0;
+
+void bullet_spawn(Game *g, float x, float y, int target_unit, int target_bld,
+                  float dmg, Faction f, int kind) {
+    if (g->bullet_count >= MAX_BULLETS) return;
+    Bullet *b = &g->bullets[g->bullet_count++];
+    b->x = x; b->y = y;
+    b->target_unit = target_unit;
+    b->target_bld = target_bld;
+    b->damage = dmg;
+    b->faction = f;
+    b->kind = kind;
+    b->speed = (kind == 3) ? 320 : (kind == 1 ? 420 : 520);
+    b->life = 3.0f;
+    if (target_unit >= 0) {
+        Unit *t = unit_by_id(g, target_unit);
+        if (t) { b->tx = t->x; b->ty = t->y; }
+    } else if (target_bld >= 0) {
+        Building *t = bld_by_id(g, target_bld);
+        if (t) { b->tx = (float)(t->tx*TILE + t->w*TILE/2);
+                 b->ty = (float)(t->ty*TILE + t->h*TILE/2); }
+    }
+}
+
+void bullet_update(Game *g, float dt) {
+    for (int i = g->bullet_count - 1; i >= 0; i--) {
+        Bullet *b = &g->bullets[i];
+        b->life -= dt;
+        /* home onto target if still alive */
+        if (b->target_unit >= 0) {
+            Unit *t = unit_by_id(g, b->target_unit);
+            if (t) { b->tx = t->x; b->ty = t->y; }
+            else b->target_unit = -1;
+        } else if (b->target_bld >= 0) {
+            Building *t = bld_by_id(g, b->target_bld);
+            if (t) { b->tx = (float)(t->tx*TILE+t->w*TILE/2);
+                     b->ty = (float)(t->ty*TILE+t->h*TILE/2); }
+            else b->target_bld = -1;
+        }
+
+        float dx = b->tx - b->x, dy = b->ty - b->y;
+        float d = (float)sqrtf(dx*dx + dy*dy);
+        float step = b->speed * dt;
+        if (d <= step + 4 || b->life <= 0) {
+            /* impact */
+            if (b->target_unit >= 0) {
+                Unit *t = unit_by_id(g, b->target_unit);
+                if (t) unit_apply_damage(g, t, b->damage);
+            } else if (b->target_bld >= 0) {
+                Building *t = bld_by_id(g, b->target_bld);
+                if (t) bld_apply_damage(g, t, b->damage);
+            }
+            particle_burst(g, b->tx, b->ty, 4,
+                           (b->kind==2)?2:1, 255, 200, 80);
+            /* swap-remove */
+            g->bullets[i] = g->bullets[g->bullet_count - 1];
+            g->bullet_count--;
+            continue;
+        }
+        b->x += dx/d * step;
+        b->y += dy/d * step;
+        /* trail */
+        if (b->kind != 0)
+            particle_spawn(g, b->x, b->y, 2, 255, 180, 60);
+    }
+}
+
+void particle_spawn(Game *g, float x, float y, int kind, uint8_t cr, uint8_t cg, uint8_t cb) {
+    if (g->particle_count >= MAX_PARTICLES) return;
+    if (!g_prng_init) { rng_seed(&g_prng, 0x1234ABCDULL); g_prng_init = 1; }
+    Particle *p = &g->particles[g->particle_count++];
+    p->x = x; p->y = y;
+    float ang = rng_frange(&g_prng, 0, 6.283f);
+    float sp = rng_frange(&g_prng, 10, 60);
+    p->vx = (float)cosf(ang) * sp;
+    p->vy = (float)sinf(ang) * sp;
+    p->life = p->max_life = (kind == 0) ? 1.2f : 0.5f;
+    p->r = cr; p->g = cg; p->b = cb;
+    p->kind = kind;
+}
+
+void particle_burst(Game *g, float x, float y, int n, int kind, uint8_t cr, uint8_t cg, uint8_t cb) {
+    for (int i = 0; i < n; i++) particle_spawn(g, x, y, kind, cr, cg, cb);
+}
+
+void particle_update(Game *g, float dt) {
+    for (int i = g->particle_count - 1; i >= 0; i--) {
+        Particle *p = &g->particles[i];
+        p->life -= dt;
+        p->x += p->vx * dt;
+        p->y += p->vy * dt;
+        p->vx *= 0.92f; p->vy *= 0.92f;
+        if (p->kind == 1) p->vy += 40 * dt; /* fire rises/slows */
+        if (p->life <= 0) {
+            g->particles[i] = g->particles[g->particle_count - 1];
+            g->particle_count--;
+        }
+    }
+}