ray: libize raytracer core, introduces src/libs

This is the first step of breaking out all the core rendering stuffs
into reusable libraries and making modules purely compositional,
consumers of various included rendering/effects libraries.

Expect multiple modules leveraging libray for a variety of scenes and
such.  Also expect compositions mixing the various libraries for more
interesting visuals.

1 files changed, 70 insertions, 0 deletions

diff --git a/src/libs/ray/ray_camera.c b/src/libs/ray/ray_camera.c
new file mode 100644
index 0000000..b942cf3
--- /dev/null
+++ b/src/libs/ray/ray_camera.c
@@ -0,0 +1,70 @@
+#include "fb.h"
+
+#include "ray_camera.h"
+#include "ray_euler.h"
+
+
+/* Produce a vector from the provided orientation vectors and proportions. */
+static ray_3f_t project_corner(ray_3f_t *forward, ray_3f_t *left, ray_3f_t *up, float focal_length, float horiz, float vert)
+{
+	ray_3f_t	tmp;
+	ray_3f_t	corner;
+
+	corner = ray_3f_mult_scalar(forward, focal_length);
+	tmp = ray_3f_mult_scalar(left, horiz);
+	corner = ray_3f_add(&corner, &tmp);
+	tmp = ray_3f_mult_scalar(up, vert);
+	corner = ray_3f_add(&corner, &tmp);
+
+	return ray_3f_normalize(&corner);
+}
+
+
+/* Produce vectors for the corners of the entire camera frame, used for interpolation. */
+static void project_corners(const ray_camera_t *camera, ray_camera_frame_t *frame)
+{
+	ray_3f_t	forward, left, up, right, down;
+	float		half_horiz = (float)camera->width * 0.5f;
+	float		half_vert = (float)camera->height * 0.5f;
+
+	ray_euler_basis(&camera->orientation, &forward, &up, &left);
+	right = ray_3f_negate(&left);
+	down = ray_3f_negate(&up);
+
+	frame->nw = project_corner(&forward, &left, &up, camera->focal_length, half_horiz, half_vert);
+	frame->ne = project_corner(&forward, &right, &up, camera->focal_length, half_horiz, half_vert);
+	frame->se = project_corner(&forward, &right, &down, camera->focal_length, half_horiz, half_vert);
+	frame->sw = project_corner(&forward, &left, &down, camera->focal_length, half_horiz, half_vert);
+}
+
+
+/* Prepare a frame of camera projection, initializing res_frame. */
+void ray_camera_frame_prepare(const ray_camera_t *camera, ray_camera_frame_t *res_frame)
+{
+	res_frame->camera = camera;
+
+	project_corners(camera, res_frame);
+
+	res_frame->x_delta = 1.0f / (float)camera->width;
+	res_frame->y_delta = 1.0f / (float)camera->height;
+}
+
+
+/* Begin a frame's fragment, initializing frame and ray. */
+void ray_camera_fragment_begin(ray_camera_frame_t *frame, fb_fragment_t *fb_fragment, ray_ray_t *res_ray, ray_camera_fragment_t *res_fragment)
+{
+	res_fragment->frame = frame;
+	res_fragment->fb_fragment = fb_fragment;
+	res_fragment->ray = res_ray;
+
+	res_fragment->x = res_fragment->y = 0;
+
+	res_fragment->x_alpha = frame->x_delta * (float)fb_fragment->x;
+	res_fragment->y_alpha = frame->y_delta * (float)fb_fragment->y;
+
+	res_fragment->cur_w = ray_3f_lerp(&frame->nw, &frame->sw, res_fragment->y_alpha);
+	res_fragment->cur_e = ray_3f_lerp(&frame->ne, &frame->se, res_fragment->y_alpha);
+
+	res_ray->origin = frame->camera->position;
+	res_ray->direction = ray_3f_nlerp(&res_fragment->cur_w, &res_fragment->cur_e, res_fragment->x_alpha);
+}