Fix accidental switch/teleporter behavior changes

[neverball] / share / vec3.c

diff --git a/share/vec3.c b/share/vec3.c
index bb125d9..60daf3c 100644 (file)
--- a/share/vec3.c
+++ b/share/vec3.c
@@ -299,7 +299,7 @@ void m_view(float *M,
 
 void q_as_axisangle(const float q[4], float u[3], float *a)
 {
-    *a = V_DEG(2.0f * facosf(q[0]));
+    *a = 2.0f * facosf(q[0]);
     v_nrm(u, q + 1);
 }
 
@@ -381,4 +381,66 @@ void q_euler(float v[3], const float q[4])
     v[2] = fatan2f(m23, m33);
 }
 
+/*
+ * Spherical linear interpolation
+ */
+void q_slerp(float q[4], const float a[4], const float b[4], float t)
+{
+    float c, r, s, u, v;
+    int i = +1;
+
+    if (t <= 0.0f)
+    {
+        q_cpy(q, a);
+        return;
+    }
+
+    if (1.0f <= t)
+    {
+        q_cpy(q, b);
+        return;
+    }
+
+    /*
+     * a . b = |a||b| cos A
+     * |a| = |b| = 1
+     */
+
+    c = q_dot(a, b);
+
+    /* Ensure the shortest path. */
+
+    if (c < 0)
+    {
+        c = -c;
+        i = -1;
+    }
+
+    /* Fall back to normalized lerp for very similar orientations. */
+
+    if (1.0f - c < TINY)
+    {
+        u = 1.0f - t;
+        v = t;
+
+        i = 1;
+    }
+    else
+    {
+        r = facosf(c);
+        s = fsinf(r);
+        u = fsinf((1.0f - t) * r) / s;
+        v = fsinf((t)        * r) / s * i;
+
+        i = 0;
+    }
+
+    q[0] = a[0] * u + b[0] * v;
+    q[1] = a[1] * u + b[1] * v;
+    q[2] = a[2] * u + b[2] * v;
+    q[3] = a[3] * u + b[3] * v;
+
+    if (i) q_nrm(q, q);
+}
+
 /*---------------------------------------------------------------------------*/