Make raytracing engine multi-threaded.

5 files changed, 116 insertions, 25 deletions

diff --git a/libdimension/Makefile.am b/libdimension/Makefile.am
index 91d0af0..2b5784a 100644
--- a/libdimension/Makefile.am
+++ b/libdimension/Makefile.am
@@ -21,6 +21,6 @@ nobase_include_HEADERS = dimension.h dimension/array.h dimension/camera.h dimens
 
 lib_LTLIBRARIES = libdimension.la
 
-libdimension_la_SOURCES = $(nobase_include_HEADERS) array.c camera.c canvas.c color.c cube.c error.c geometry.c png.c object.c scene.c sphere.c
+libdimension_la_SOURCES = $(nobase_include_HEADERS) array.c camera.c canvas.c color.c cube.c error.c geometry.c png.c object.c raytrace.c scene.c sphere.c
 libdimension_la_LDFLAGS = -version-info 0:0:0
 libdimension_la_LIBADD  = -lm -lpthread -lpng
diff --git a/libdimension/array.c b/libdimension/array.c
index e6e4363..88eb88f 100644
--- a/libdimension/array.c
+++ b/libdimension/array.c
@@ -53,6 +53,15 @@ dmnsn_array_pop(dmnsn_array *array, void *obj)
   dmnsn_array_resize(array, array->length - 1);
 }
 
+void *
+dmnsn_array_at(dmnsn_array *array, size_t i)
+{
+  if (i >= array->length) {
+    dmnsn_error(DMNSN_SEVERITY_HIGH, "Array index out of bounds.");
+  }
+  return array->ptr + array->obj_size*i;
+}
+
 void
 dmnsn_array_get(const dmnsn_array *array, size_t i, void *obj)
 {
diff --git a/libdimension/dimension/array.h b/libdimension/dimension/array.h
index 9ee3584..0a64952 100644
--- a/libdimension/dimension/array.h
+++ b/libdimension/dimension/array.h
@@ -38,8 +38,9 @@ dmnsn_array *dmnsn_new_array(size_t obj_size);
 void dmnsn_array_push(dmnsn_array *array, const void *obj);
 void dmnsn_array_pop(dmnsn_array *array, void *obj);
 
-void dmnsn_array_get(const dmnsn_array *array, size_t i, void *obj);
-void dmnsn_array_set(dmnsn_array *array, size_t i, const void *obj);
+void *dmnsn_array_at(dmnsn_array *array, size_t i);
+void  dmnsn_array_get(const dmnsn_array *array, size_t i, void *obj);
+void  dmnsn_array_set(dmnsn_array *array, size_t i, const void *obj);
 
 void dmnsn_array_resize(dmnsn_array *array, size_t length);
 
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);
+        }
+      }
+    }
+  }
+}
diff --git a/libdimension/scene.c b/libdimension/scene.c
index 4a84823..048ad45 100644
--- a/libdimension/scene.c
+++ b/libdimension/scene.c
@@ -38,25 +38,3 @@ dmnsn_delete_scene(dmnsn_scene *scene)
     free(scene);
   }
 }
-
-void
-dmnsn_raytrace_scene(dmnsn_scene *scene)
-{
-  unsigned int i, j;
-  dmnsn_object *object;
-  dmnsn_line ray;
-
-  dmnsn_array_get(scene->objects, 0, &object);
-
-  for (i = 0; i < scene->canvas->x; ++i) {
-    for (j = 0; j < scene->canvas->y; ++j) {
-      ray = (*scene->camera->ray_fn)(scene->camera, scene->canvas, i, j);
-      if ((*object->intersections_fn)(object, ray)->length > 0) {
-        dmnsn_set_pixel(scene->canvas, i, j,
-                        dmnsn_color_from_XYZ(dmnsn_whitepoint));
-      } else {
-        dmnsn_set_pixel(scene->canvas, i, j, scene->background);
-      }
-    }
-  }
-}