Make raytracing engine multi-threaded.

1 files changed, 103 insertions, 0 deletions

diff --git a/libdimension/raytrace.c b/libdimension/raytrace.c
new file mode 100644
index 0000000..5d728d5
--- /dev/null
+++ b/libdimension/raytrace.c
@@ -0,0 +1,103 @@
+/*************************************************************************
+ * Copyright (C) 2008 Tavian Barnes <tavianator@gmail.com>               *
+ *                                                                       *
+ * This file is part of The Dimension Library.                           *
+ *                                                                       *
+ * The Dimension Library is free software; you can redistribute it and/  *
+ * or modify it under the terms of the GNU Lesser General Public License *
+ * as published by the Free Software Foundation; either version 3 of the *
+ * License, or (at your option) any later version.                       *
+ *                                                                       *
+ * The Dimension Library 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  *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+#include "dimension.h"
+#include <unistd.h> /* For sysconf */
+
+typedef struct {
+  dmnsn_scene *scene;
+  unsigned int i, n;
+} dmnsn_raytrace_thread_payload;
+
+static void *dmnsn_raytrace_scene_thread(void *arg);
+
+void
+dmnsn_raytrace_scene(dmnsn_scene *scene)
+{
+  long n = sysconf(_SC_NPROCESSORS_ONLN);
+  unsigned int i;
+  pthread_t thread;
+  dmnsn_raytrace_thread_payload payload;
+  dmnsn_array *threads, *payloads;
+
+  threads  = dmnsn_new_array(sizeof(pthread_t));
+  payloads = dmnsn_new_array(sizeof(dmnsn_raytrace_thread_payload));
+
+  if (n <= 0) n = 1;
+
+  payload.scene = scene;
+  payload.n = n;
+  for (i = 0; i < n; ++i) {
+    payload.i = i;
+    dmnsn_array_push(payloads, &payload);
+
+    pthread_create(&thread, NULL, &dmnsn_raytrace_scene_thread,
+                   dmnsn_array_at(payloads, i));
+    dmnsn_array_push(threads, &thread);
+  }
+
+  for (i = 0; i < n; ++i) {
+    dmnsn_array_get(threads, i, &thread);
+    pthread_join(thread, NULL);
+  }
+
+  dmnsn_delete_array(payloads);
+  dmnsn_delete_array(threads);
+}
+
+/* Raytrace a scene */
+static void *
+dmnsn_raytrace_scene_thread(void *arg)
+{
+  unsigned int i, j, k;
+  dmnsn_object *object;
+  dmnsn_line ray;
+  dmnsn_raytrace_thread_payload *payload = (dmnsn_raytrace_thread_payload *)arg;
+  dmnsn_scene *scene = payload->scene;
+  dmnsn_array *intersections;
+
+  /* Iterate through each pixel */
+  for (i = 0; i < scene->canvas->x; ++i) {
+    for (j = 0; j < scene->canvas->y; ++j) {
+      /* Only do the pixels assigned to this thread */
+      if ((j*scene->canvas->x + i)%payload->n == payload->i) {
+        /* Set the pixel to the background color */
+        dmnsn_set_pixel(scene->canvas, i, j, scene->background);
+
+        /* Get the ray corresponding to the (i,j)th pixel */
+        ray = (*scene->camera->ray_fn)(scene->camera, scene->canvas, i, j);
+        
+        for (k = 0; k < scene->objects->length; ++k) {
+          dmnsn_array_get(scene->objects, k, &object);
+          /* Test for an intersection with an object */
+          intersections = (*object->intersections_fn)(object, ray);
+          if (intersections->length > 0) {
+            /* Mark intersections white */
+            dmnsn_set_pixel(scene->canvas, i, j,
+                            dmnsn_color_from_XYZ(dmnsn_whitepoint));
+            dmnsn_delete_array(intersections);
+            break;
+          }
+          dmnsn_delete_array(intersections);
+        }
+      }
+    }
+  }
+}