polyadvent

commit ab66e332265639a252e3d3c9b679b64b04836ac1
parent e73ab2ac56a742e586fb72efa6934a750d846565
Author: William Casarin <jb55@jb55.com>
Date:   Mon, 30 Apr 2018 14:27:47 -0700

initial quaternion stuff

Diffstat:
A
src/quat.c
 | 
38
++++++++++++++++++++++++++++++++++++++
A
src/quat.h
 | 
12
++++++++++++

2 files changed, 50 insertions(+), 0 deletions(-)
diff --git a/src/quat.c b/src/quat.c
@@ -0,0 +1,38 @@
+
+#include "quat.h"
+#include <math.h>
+
+void quat_id(quat *dest) {
+  dest[0] = 0;
+  dest[1] = 0;
+  dest[2] = 0;
+  dest[3] = 1;
+}
+
+void quat_multiply(quat *a, quat *b, quat *dest) {
+  float ax = a[0];
+  float ay = a[1];
+  float az = a[2];
+  float aw = a[3];
+
+  float bx = b[0];
+  float by = b[1];
+  float bz = b[2];
+  float bw = b[3];
+
+  dest[0] = ax * bw + aw * bx + ay * bz - az * by;
+  dest[1] = ay * bw + aw * by + az * bx - ax * bz;
+  dest[2] = az * bw + aw * bz + ax * by - ay * bx;
+  dest[3] = aw * bw - ax * bx - ay * by - az * bz;
+}
+
+
+void quat_axis_angle(float *axis, float angle, quat *dest) {
+  float half_angle = angle / 2.0;
+  float s = sin(half_angle);
+
+  dest[0] = axis[0] * s;
+  dest[1] = axis[1] * s;
+  dest[2] = axis[2] * s;
+  dest[3] = cos(half_angle);
+}
diff --git a/src/quat.h b/src/quat.h
@@ -0,0 +1,12 @@
+
+
+#ifndef POLYADVENT_QUAT4_
+#define POLYADVENT_QUAT4_
+
+typedef float quat;
+
+void quat_id(quat *dest);
+void quat_multiply(quat *a, quat *b, quat *dest);
+void quat_axis_angle(float *axis, float angle, quat *dest);
+
+#endif /* POLYADVENT_QUAT4_ */