From b08d3b7b1b06fd2e9dd09eef248a10d33b8d1742 Mon Sep 17 00:00:00 2001
From: jacopo grandi <jak.sk8@hotmail.it>
Date: Sat, 6 Mar 2021 13:06:09 +0100
Subject: gst interpolations, particle systems, timing and gui fix

---
 gst/fxs.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 92 insertions(+), 6 deletions(-)

(limited to 'gst/fxs.c')

diff --git a/gst/fxs.c b/gst/fxs.c
index 25ddf18..9e3aef4 100644
--- a/gst/fxs.c
+++ b/gst/fxs.c
@@ -1,5 +1,6 @@
 #include <stdlib.h>
 #include <stdio.h>
+#include <math.h>
 
 #include "../umath/vec.h"
 
@@ -7,31 +8,105 @@
 #include "units.h"
 
 void fx_init (fxs *fx) {
-    fx->bullets = (bullet*)malloc(sizeof(bullet)*1024);
+    fx->bullets = (bullet*)malloc(sizeof(bullet)*FXS_BULLET_MAX);
     fx->bulletslen = 0;
+    fx->explosions = (explosion*)malloc(sizeof(explosion)*FXS_EXPLOSION_MAX);
+    fx->explosionslen = 0;
 }
 
 void fx_add_bullet (fxs *fx, bullet *b) {
-    if (fx->bulletslen >= 1024-1) return;
+    if (fx->bulletslen >= FXS_BULLET_MAX-1) return;
     fx->bullets[fx->bulletslen] = *b;
     fx->bulletslen++;
 }
 
+void fx_spread_to_head (float spread, float head[]) {
+    head[0] = 1-spread; if (spread<0.5) head[0] = spread;
+    head[1] = 1-spread*2;
+    vec2_norm(head);
+}
+
+/*
+ * param: pos is the center of the explosion
+ * param: vel is the heading of the explosion
+ * param: force is added to vel and scaled by mass
+ * param: spread [0, 1] is half the angle of the explosion
+ * param: speed [0, inf] is the initial speed
+ */
+void fx_explosion_init (fxs *fx, explosion *e, 
+    float pos[], float vel[], float color[], float force[],
+    float spread, float speed, int n, float time, float lifetime) 
+{
+    float normvel[2] = { vel[0], vel[1] }; vec2_norm(normvel);
+    float perpvel[2] = { normvel[1], -normvel[0] };
+    e->pos[0] = pos[0]; e->pos[1] = pos[1];
+    e->partslen = n;
+    e->force[0] = force[0]; e->force[1] = force[1];
+    e->starttime = time;
+    e->friction = 0.95;
+    for (int j=0; j<n; j++) {
+        particle *p = e->parts+j;
+        float sample = rand()%1000/1000.0 * spread;
+        float head[2]; fx_spread_to_head(sample, head);
+        if (j%2 == 0) head[0] *= -1;
+        float dir[2] = {
+            -head[0]*normvel[1] - head[1]*perpvel[1],
+            head[0]*normvel[0] + head[1]*perpvel[0]
+        }; 
+        p->lifetime = lifetime;
+        p->mass = 1;
+        p->pos[0] = pos[0]; p->pos[1] = pos[1];
+        p->vel[0] = dir[0]; p->vel[1] = dir[1];
+        vec2_mul(p->vel, p->vel, speed+(rand()%1000)/1000.0*speed/2);
+        p->color[0] = color[0];
+        p->color[1] = color[1];
+        p->color[2] = color[2];
+    }
+}
+
+void fx_add_explosion (fxs *fx, explosion *e) {
+    if (fx->explosionslen >= FXS_EXPLOSION_MAX-1) return;
+    fx->explosions[fx->explosionslen] = *e;
+    fx->explosionslen++;
+}
+
 void fx_process (fxs *fx, float time) {
     for (int i=0; i<fx->bulletslen; i++) {
         bullet *b = fx->bullets+i;
+        if (b->starttime > time) continue;
         if (time > b->endtime) {
             // remove by replacing with last, dont care for order
             *b = fx->bullets[fx->bulletslen-1];
             fx->bulletslen--;
         }
     }
+    
+    for (int i=0; i<fx->explosionslen; i++) {
+        explosion *e = fx->explosions+i;
+        if (e->starttime > time) continue;
+        int sum = e->partslen;
+        for (int j=0; j<e->partslen; j++) {
+            if (e->starttime + e->parts[j].lifetime >= time) {
+                vec2_add(e->parts[j].pos, e->parts[j].pos, e->parts[j].vel);
+                float forcemass[2]; 
+                vec2_mul(forcemass, e->force, e->parts[j].mass);
+                vec2_add(e->parts[j].vel, e->parts[j].vel, forcemass);
+                vec2_mul(e->parts[j].vel, e->parts[j].vel, e->friction);
+            } else { sum -= 1; }
+        }
+        if (sum == 0) {
+            // remove by replacing with last, dont care for order
+            *e = fx->explosions[fx->explosionslen-1];
+            fx->explosionslen--;
+        }
+    }
 }
 
 
 void fx_render (SDL_Renderer *rend, fxs *fx, float cam[], float time) {
     for (int i=0; i<fx->bulletslen; i++) {
         bullet *b = fx->bullets+i;
+        if (b->starttime > time) continue;
         float travel_time = b->endtime - b->starttime;
         float interval_time = time - b->starttime;
         float amt = interval_time / travel_time;
@@ -46,10 +121,7 @@ void fx_render (SDL_Renderer *rend, fxs *fx, float cam[], float time) {
         if (dist < 10) { mag = dist; }
         vec2_norm(head); vec2_mul(head, head, mag);
         SDL_SetRenderDrawColor(rend, 
-            b->color[0], 
-            b->color[1], 
-            b->color[2],
-            255);
+            b->color[0], b->color[1], b->color[2], 255);
         SDL_RenderDrawLine(rend, 
             -cam[0] + pos[0], 
             -cam[1] + pos[1],
@@ -57,4 +129,18 @@ void fx_render (SDL_Renderer *rend, fxs *fx, float cam[], float time) {
             -cam[1] + pos[1] + head[1]
         );
     }
+    
+    for (int i=0; i<fx->explosionslen; i++) {
+        explosion *e = fx->explosions+i;
+        if (e->starttime > time) continue;
+        for (int j=0; j<e->partslen; j++) {
+            particle *p = e->parts+j;
+            if (e->starttime + p->lifetime >= time) {
+                SDL_SetRenderDrawColor(rend, 
+                    p->color[0], p->color[1],  p->color[2], 255);
+                SDL_RenderDrawPoint(rend, 
+                    -cam[0] + p->pos[0], -cam[1] + p->pos[1]);
+            }
+        }
+    }
 }
-- 
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