move raycastign to its own file

1 files changed, 106 insertions, 0 deletions

diff --git a/src/ray.c b/src/ray.c
new file mode 100644
index 0000000..36e89b4
--- /dev/null
+++ b/src/ray.c
@@ -0,0 +1,106 @@
+#include "ray.h"
+#include "map.h"
+
+#include <math.h>
+
+float v2_cross(v2 a, v2 b) {
+    return fabs(a.x * b.y - a.y * b.x);
+}
+
+float v2_len(v2 a) {
+    return sqrt(a.x * a.x + a.y * a.y);
+}
+
+float v2_square_dist(v2 a, v2 b) {
+    return pow(a.x - b.x, 2) + pow(a.y - b.y, 2);
+}
+
+#define PI		3.14159265358979323846
+#define PIH		1.57079632679489661923
+#define PI2		6.28318530718
+
+uint32_t cast_ray(v2 pos, float theta, v2* hit_pos) {
+
+    const v2i move = {
+        #define sign(a) ((a) < 0 ? -1 : 1)
+        sign(cos(theta)),
+        sign(sin(theta)),
+    };
+
+    const v2i offset = {
+        move.x == -1 ? 1 : 0,
+        move.y == -1 ? 1 : 0
+    };
+    
+    const float tanc = tan(theta);
+    const float cotc = tan(PIH - (theta));
+
+    v2i posi = {
+        (int)pos.x + offset.x,
+        (int)pos.y + offset.y
+    };
+
+    bool fx = false;
+    uint32_t vx = 0;
+    float x;
+
+    while (!fx) {
+        posi.y += move.y;
+        x = cotc * (posi.y - pos.y) + pos.x;
+        
+        if (fabs(x) - pos.x >= MAP_SIZE) break;
+
+        vx = value((int)x, posi.y - offset.y);
+        
+        if (vx != 0) {
+            fx = true;
+        }
+    }
+
+    bool fy = false;
+    uint32_t vy = 0;
+    float y;
+
+    while (!fy) {
+        posi.x += move.x;
+        y = tanc * (posi.x - pos.x) + pos.y;
+
+        if (fabs(y) - pos.y >= MAP_SIZE) break;
+
+        vy = value(posi.x - offset.x, (int)y);
+
+        if (vy != 0) {
+            fy = true;
+        }
+    }
+
+    uint32_t hit;
+    if (!fx && !fy) {
+        hit = 0;
+        hit_pos->x = pos.x + 1000 * move.x;
+        hit_pos->y = pos.y + 1000 * move.y;
+        return false;
+    } else if (fx && !fy) {
+        hit = vx;
+        hit_pos->x = x;
+        hit_pos->y = posi.y;
+    } else if (fy && !fx) {
+        hit = vy;
+        hit_pos->x = posi.x;
+        hit_pos->y = y;
+    } else {
+        const v2 posx = {x, posi.y};
+        const v2 posy = {posi.x, y};
+        if (v2_square_dist(posx, pos) < v2_square_dist(posy, pos)) {
+            hit = vx;
+            hit_pos->x = x;
+            hit_pos->y = posi.y;
+        } else {
+            hit = vy;
+            hit_pos->x = posi.x;
+            hit_pos->y= y;
+        }
+    }
+
+    return hit;
+}