Fail.

1 files changed, 36 insertions, 0 deletions

diff --git a/3dmath.c b/3dmath.c
new file mode 100644
index 0000000..d729323
--- /dev/null
+++ b/3dmath.c
@@ -0,0 +1,36 @@
+#include <math.h>
+
+#define POW2(x) ((x) * (x))
+
+float
+dot(float x[3], float y[3]) {
+    return x[0] * y[0] + x[1] * y[1] + x[2] * y[2];
+}
+
+void
+normalize(float x[3]) {
+    float len;
+    int i;
+
+    len = sqrt(dot(x, x));
+
+    for(i = 0; i < 3; ++i)
+        x[i] /= len;
+}
+
+float
+sphere_intersect(float s[3], float d[3], float c[3], float r) {
+    int i;
+    float D;
+    float v[3];
+
+    for(i = 0; i < 3; ++i)
+        v[i] = s[i] - c[i];
+
+    D = POW2(dot(v, d)) - 4 * (dot(v, v) - POW2(r));
+
+    if(D < 0)
+        return -1;
+
+    return 1;
+}