altos: Add gyro-based orientation tracking

[fw/altos] / src / core / ao_quaternion.h

diff --git a/src/core/ao_quaternion.h b/src/core/ao_quaternion.h
new file mode 100644 (file)
index 0000000..f4b8aaa
--- /dev/null
+++ b/src/core/ao_quaternion.h
@@ -0,0 +1,116 @@
+/*
+ * Copyright © 2013 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#ifndef _AO_QUATERNION_H_
+#define _AO_QUATERNION_H_
+
+#include <math.h>
+
+struct ao_quaternion {
+       float   r;              /* real bit */
+       float   x, y, z;        /* imaginary bits */
+};
+
+static inline void ao_quaternion_multiply(struct ao_quaternion *r,
+                                         struct ao_quaternion *a,
+                                         struct ao_quaternion *b)
+{
+       struct ao_quaternion    t;
+#define T(_a,_b)       (((a)->_a) * ((b)->_b))
+       t.r = T(r,r) - T(x,x) - T(y,y) - T(z,z);
+       t.x = T(r,x) + T(x,r) + T(y,z) - T(z,y);
+       t.y = T(r,y) - T(x,z) + T(y,r) + T(z,x);
+       t.z = T(r,z) + T(x,y) - T(y,x) + T(z,r);
+#undef T
+       *r = t;
+}
+
+static inline void ao_quaternion_conjugate(struct ao_quaternion *r,
+                                          struct ao_quaternion *a)
+{
+       r->r = a->r;
+       r->x = -a->x;
+       r->y = -a->y;
+       r->z = -a->z;
+}
+
+static inline float ao_quaternion_normal(struct ao_quaternion *a)
+{
+#define S(_a)  (((a)->_a) * ((a)->_a))
+       return S(r) + S(x) + S(y) + S(z);
+#undef S
+}
+
+static inline void ao_quaternion_scale(struct ao_quaternion *r,
+                                      struct ao_quaternion *a,
+                                      float b)
+{
+       r->r = a->r * b;
+       r->x = a->x * b;
+       r->y = a->y * b;
+       r->z = a->z * b;
+}
+
+static inline void ao_quaternion_normalize(struct ao_quaternion *r,
+                                          struct ao_quaternion *a)
+{
+       float   n = ao_quaternion_normal(a);
+
+       if (n > 0)
+               ao_quaternion_scale(r, a, 1/sqrtf(n));
+       else
+               *r = *a;
+}
+
+static inline void ao_quaternion_rotate(struct ao_quaternion *r,
+                                       struct ao_quaternion *a,
+                                       struct ao_quaternion *b)
+{
+       struct ao_quaternion    c;
+       struct ao_quaternion    t;
+
+       ao_quaternion_conjugate(&c, b);
+       ao_quaternion_multiply(&t, b, a);
+       ao_quaternion_multiply(r, &t, &c);
+}
+
+static inline void ao_quaternion_init_vector(struct ao_quaternion *r,
+                                            float x, float y, float z)
+{
+       r->r = 0;
+       r->x = x;
+       r->y = y;
+       r->z = z;
+}
+
+static inline void ao_quaternion_init_rotation(struct ao_quaternion *r,
+                                              float x, float y, float z,
+                                              float s, float c)
+{
+       r->r = c;
+       r->x = s * x;
+       r->y = s * y;
+       r->z = s * z;
+}
+
+static inline void ao_quaternion_init_zero_rotation(struct ao_quaternion *r)
+{
+       r->r = 1;
+       r->x = r->y = r->z = 0;
+}
+
+#endif /* _AO_QUATERNION_H_ */