ray: implement all orders in ray_euler_basis()

Originally I only implemented pitch->yaw->roll, and being new to all this
didn't fully appreciate the limitation that resulted in.

This adds all six permutations of pitch/yaw/roll, the scene must specify
the desired order when setting up the camera with the euler angles, see
the enum in ray_euler.h.

4 files changed, 106 insertions, 27 deletions

diff --git a/src/modules/ray/Makefile.am b/src/modules/ray/Makefile.am
index 6c9a50a..7acfdd8 100644
--- a/src/modules/ray/Makefile.am
+++ b/src/modules/ray/Makefile.am
@@ -1,4 +1,4 @@
 noinst_LIBRARIES = libray.a
-libray_a_SOURCES = ray_3f.h ray.c ray_camera.c ray_camera.h ray_color.h ray_euler.h ray.h ray_light_emitter.h ray_object.c ray_object.h ray_object_light.h ray_object_plane.h ray_object_point.h ray_object_sphere.h ray_object_type.h ray_ray.h ray_scene.c ray_scene.h ray_surface.h ray_threads.c ray_threads.h
+libray_a_SOURCES = ray_3f.h ray.c ray_camera.c ray_camera.h ray_color.h ray_euler.c ray_euler.h ray.h ray_light_emitter.h ray_object.c ray_object.h ray_object_light.h ray_object_plane.h ray_object_point.h ray_object_sphere.h ray_object_type.h ray_ray.h ray_scene.c ray_scene.h ray_surface.h ray_threads.c ray_threads.h
 libray_a_CFLAGS = @ROTOTILLER_CFLAGS@ -ffast-math
 libray_a_CPPFLAGS = @ROTOTILLER_CFLAGS@ -I@top_srcdir@/src
diff --git a/src/modules/ray/ray.c b/src/modules/ray/ray.c
index 60d08cf..951b1d7 100644
--- a/src/modules/ray/ray.c
+++ b/src/modules/ray/ray.c
@@ -90,6 +90,7 @@ static void ray(fb_fragment_t *fragment)
 	ray_camera_t		camera = {
 					.position = { .x = 0.0, .y = 0.0, .z = 6.0 },
 					.orientation = {
+						.order = RAY_EULER_ORDER_YPR, /* yaw,pitch,roll */
 						.yaw = RAY_EULER_DEGREES(0.0f),
 						.pitch = RAY_EULER_DEGREES(0.0f),
 						.roll = RAY_EULER_DEGREES(180.0f),
diff --git a/src/modules/ray/ray_euler.c b/src/modules/ray/ray_euler.c
new file mode 100644
index 0000000..8709fa3
--- /dev/null
+++ b/src/modules/ray/ray_euler.c
@@ -0,0 +1,90 @@
+#include <assert.h>
+#include <math.h>
+
+#include "ray_3f.h"
+#include "ray_euler.h"
+
+/* produce orthonormal basis vectors from euler angles, rotated in the specified order */
+void ray_euler_basis(ray_euler_t *e, ray_3f_t *forward, ray_3f_t *up, ray_3f_t *left)
+{
+	float	cos_yaw = cosf(e->yaw);
+	float	sin_yaw = sinf(e->yaw);
+	float	cos_roll = cosf(e->roll);
+	float	sin_roll = sinf(e->roll);
+	float	cos_pitch = cosf(e->pitch);
+	float	sin_pitch = sinf(e->pitch);
+
+	/* Rotation matrices from http://www.songho.ca/opengl/gl_anglestoaxes.html */
+	switch (e->order) {
+	case RAY_EULER_ORDER_PYR:
+		/* pitch, yaw, roll */
+		up->x = -cos_yaw * sin_roll;
+		up->y = -sin_pitch * sin_yaw * sin_roll + cos_pitch * cos_roll;
+		up->z = cos_pitch * sin_yaw * sin_roll + sin_pitch * cos_roll;
+
+		forward->x = sin_yaw;
+		forward->y = -sin_pitch * cos_yaw;
+		forward->z = cos_pitch * cos_yaw;
+		break;
+
+	case RAY_EULER_ORDER_YRP:
+		/* yaw, roll, pitch */
+		up->x = -cos_yaw * sin_roll * cos_pitch + sin_yaw * sin_pitch;
+		up->y = cos_roll * cos_pitch;
+		up->z = sin_yaw * sin_roll * cos_pitch + cos_yaw * sin_pitch;
+
+		forward->x = cos_yaw * sin_roll * sin_pitch + sin_yaw * cos_pitch;
+		forward->y = -cos_roll * sin_pitch;
+		forward->z = -sin_yaw * sin_roll * sin_pitch + cos_yaw * cos_pitch;
+		break;
+
+	case RAY_EULER_ORDER_RPY:
+		/* roll, pitch, yaw */
+		up->x = -sin_roll * cos_pitch;
+		up->y = cos_roll * cos_pitch;
+		up->z = sin_pitch;
+
+		forward->x = cos_roll * sin_yaw + sin_roll * sin_pitch * cos_yaw;
+		forward->y = sin_roll * sin_yaw - cos_roll * sin_pitch * cos_yaw;
+		forward->z = cos_pitch * cos_yaw;
+		break;
+
+	case RAY_EULER_ORDER_PRY:
+		/* pitch, roll, yaw */
+		up->x = -sin_roll;
+		up->y = cos_pitch * cos_roll;
+		up->z = sin_pitch * cos_roll;
+
+		forward->x = cos_roll * sin_yaw;
+		forward->y = cos_pitch * sin_roll * sin_yaw - sin_pitch * cos_yaw;
+		forward->z = sin_pitch * sin_roll * sin_yaw + cos_pitch * cos_yaw;
+		break;
+
+	case RAY_EULER_ORDER_RYP:
+		/* roll, yaw, pitch */
+		up->x = -sin_roll * cos_pitch + cos_roll * sin_yaw * sin_pitch;
+		up->y = cos_roll * cos_pitch + sin_roll * sin_yaw * sin_pitch;
+		up->z = cos_yaw * sin_pitch;
+
+		forward->x = sin_roll * sin_pitch + cos_roll * sin_yaw * cos_pitch;
+		forward->y = -cos_roll * sin_pitch + sin_roll * sin_yaw * cos_pitch;
+		forward->z = cos_yaw * cos_pitch;
+		break;
+
+	case RAY_EULER_ORDER_YPR:
+		/* yaw, pitch, roll */
+		up->x = -cos_yaw * sin_roll + sin_yaw * sin_pitch * cos_roll;
+		up->y = cos_pitch * cos_roll;
+		up->z = sin_yaw * sin_roll + cos_yaw * sin_pitch * cos_roll;
+
+		forward->x = sin_yaw * cos_pitch;
+		forward->y = -sin_pitch;
+		forward->z = cos_yaw * cos_pitch;
+		break;
+
+	default:
+		assert(0);
+	}
+
+	*left = ray_3f_cross(up, forward);
+}
diff --git a/src/modules/ray/ray_euler.h b/src/modules/ray/ray_euler.h
index 86f5221..3a74cab 100644
--- a/src/modules/ray/ray_euler.h
+++ b/src/modules/ray/ray_euler.h
@@ -5,12 +5,22 @@
 
 #include "ray_3f.h"
 
+/* Desired order to apply euler angle rotations */
+typedef enum ray_euler_order_t {
+	RAY_EULER_ORDER_PYR,
+	RAY_EULER_ORDER_YRP,
+	RAY_EULER_ORDER_RPY,
+	RAY_EULER_ORDER_PRY,
+	RAY_EULER_ORDER_RYP,
+	RAY_EULER_ORDER_YPR,
+} ray_euler_order_t;
 
 /* euler angles are convenient for describing orientation */
 typedef struct ray_euler_t {
-	float	pitch;	/* pitch in radiasn */
-	float	yaw;	/* yaw in radians */
-	float	roll;	/* roll in radians */
+	ray_euler_order_t	order;	/* order to apply rotations in */
+	float			pitch;	/* pitch in radiasn */
+	float			yaw;	/* yaw in radians */
+	float			roll;	/* roll in radians */
 } ray_euler_t;
 
 
@@ -18,28 +28,6 @@ typedef struct ray_euler_t {
 #define RAY_EULER_DEGREES(_deg) \
 	(_deg * (2 * M_PI / 360.0f))
 
-
-/* produce basis vectors from euler angles */
-static inline void ray_euler_basis(ray_euler_t *e, ray_3f_t *forward, ray_3f_t *up, ray_3f_t *left)
-{
-	float	cos_yaw = cosf(e->yaw);
-	float	sin_yaw = sinf(e->yaw);
-	float	cos_roll = cosf(e->roll);
-	float	sin_roll = sinf(e->roll);
-	float	cos_pitch = cosf(e->pitch);
-	float	sin_pitch = sinf(e->pitch);
-
-	forward->x = sin_yaw;
-	forward->y = -sin_pitch * cos_yaw;
-	forward->z = cos_pitch * cos_yaw;
-
-	up->x = -cos_yaw * sin_roll;
-	up->y = -sin_pitch * sin_yaw * sin_roll + cos_pitch * cos_roll;
-	up->z = cos_pitch * sin_yaw * sin_roll + sin_pitch * cos_roll;
-
-	left->x = cos_yaw * cos_roll;
-	left->y = sin_pitch * sin_yaw * cos_roll + cos_pitch * sin_roll;
-	left->z = -cos_pitch * sin_yaw * cos_roll + sin_pitch * sin_roll;
-}
+void ray_euler_basis(ray_euler_t *e, ray_3f_t *forward, ray_3f_t *up, ray_3f_t *left);
 
 #endif