*: use fragment generator

Rather than laying out all fragments in a frame up-front in
ray_module_t.prepare_frame(), return a fragment generator
(rototiller_fragmenter_t) which produces the numbered fragment
as needed.

This removes complexity from the serially-executed
prepare_frame() and allows the individual fragments to be
computed in parallel by the different threads.  It also
eliminates the need for a fragments array in the
rototiller_frame_t, indeed rototiller_frame_t is eliminated
altogether.

1 files changed, 31 insertions, 3 deletions

diff --git a/src/modules/ray/ray.c b/src/modules/ray/ray.c
index 4af9715..f442928 100644
--- a/src/modules/ray/ray.c
+++ b/src/modules/ray/ray.c
@@ -117,12 +117,38 @@ static ray_scene_t	scene = {
 static float		r;
 
 
+typedef struct ray_context_t {
+	unsigned	n_cpus;
+} ray_context_t;
+
+static void * ray_create_context(void)
+{
+	return calloc(1, sizeof(ray_context_t));
+}
+
+
+static void ray_destroy_context(void *context)
+{
+	free(context);
+}
+
+
+static int ray_fragmenter(void *context, const fb_fragment_t *fragment, unsigned num, fb_fragment_t *res_fragment)
+{
+	ray_context_t	*ctxt = context;
+
+	return fb_fragment_divide_single(fragment, ctxt->n_cpus * 64, num, res_fragment);
+}
+
+
 /* prepare a frame for concurrent rendering */
-static void ray_prepare_frame(void *context, unsigned n_cpus, fb_fragment_t *fragment, rototiller_frame_t *res_frame)
+static void ray_prepare_frame(void *context, unsigned n_cpus, fb_fragment_t *fragment, rototiller_fragmenter_t *res_fragmenter)
 {
+	ray_context_t	*ctxt = context;
+
 	/* TODO experiment with tiled fragments vs. rows */
-	res_frame->n_fragments = n_cpus * 64;
-	fb_fragment_divide(fragment, n_cpus * 64, res_frame->fragments);
+	ctxt->n_cpus = n_cpus;
+	*res_fragmenter = ray_fragmenter;
 
 	/* TODO: the camera doesn't need the width and height anymore, the fragment has the frame_width/frame_height */
 	camera.width = fragment->frame_width,
@@ -161,6 +187,8 @@ static void ray_render_fragment(void *context, fb_fragment_t *fragment)
 
 
 rototiller_module_t	ray_module = {
+	.create_context = ray_create_context,
+	.destroy_context = ray_destroy_context,
 	.prepare_frame = ray_prepare_frame,
 	.render_fragment = ray_render_fragment,
 	.name = "ray",