1 files changed, 125 insertions, 0 deletions
diff --git a/tests/OffscreenContext.cc b/tests/OffscreenContext.cc
new file mode 100644
index 0000000..f2a7e9c
--- /dev/null
+++ b/tests/OffscreenContext.cc
@@ -0,0 +1,125 @@
+#include "OffscreenContext.h"
+
+#include <GL/gl.h>
+#include <GL/glu.h>      // for gluCheckExtension
+#include <SDL.h>
+
+// Simple error reporting macros to help keep the sample code clean
+#define REPORT_ERROR_AND_EXIT(desc) { std::cout << desc << "\n"; return false; }
+#define NULL_ERROR_EXIT(test, desc) { if (!test) REPORT_ERROR_AND_EXIT(desc); }
+
+struct OffscreenContext
+{
+  int width;
+  int height;
+  GLuint fbo;
+  GLuint colorbo;
+  GLuint depthbo;
+};
+
+
+OffscreenContext *create_offscreen_context(int w, int h)
+{
+  OffscreenContext *ctx = new OffscreenContext;
+  ctx->width = w;
+  ctx->height = h;
+
+  // dummy window 
+  SDL_Init(SDL_INIT_VIDEO);
+  SDL_SetVideoMode(10,10,32,SDL_OPENGL);
+
+  /*
+   * Test if framebuffer objects are supported
+   */
+  const GLubyte* strExt = glGetString(GL_EXTENSIONS);
+  GLboolean fboSupported = gluCheckExtension((const GLubyte*)"GL_EXT_framebuffer_object", strExt);
+  if (!fboSupported)
+    REPORT_ERROR_AND_EXIT("Your system does not support framebuffer extension - unable to render scene");
+  /*
+   * Create an FBO
+   */
+  GLuint renderBuffer = 0;
+  GLuint depthBuffer = 0;
+  // Depth buffer to use for depth testing - optional if you're not using depth testing
+  glGenRenderbuffersEXT(1, &depthBuffer);
+  glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depthBuffer);
+  glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24,  w, h);
+  REPORTGLERROR("creating depth render buffer");
+
+  // Render buffer to use for imaging
+  glGenRenderbuffersEXT(1, &renderBuffer);
+  glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, renderBuffer);
+  glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGBA8, w, h);
+  REPORTGLERROR("creating color render buffer");
+  ctx->fbo = 0;
+  glGenFramebuffersEXT(1, &ctx->fbo);
+  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, ctx->fbo);
+  REPORTGLERROR("binding framebuffer");
+
+  glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, 
+                               GL_RENDERBUFFER_EXT, renderBuffer);
+  REPORTGLERROR("specifying color render buffer");
+
+  if (glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT) != 
+      GL_FRAMEBUFFER_COMPLETE_EXT)
+    REPORT_ERROR_AND_EXIT("Problem with OpenGL framebuffer after specifying color render buffer.");
+
+  glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, 
+                               GL_RENDERBUFFER_EXT, depthBuffer);
+  REPORTGLERROR("specifying depth render buffer");
+
+  if (glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT) != 
+      GL_FRAMEBUFFER_COMPLETE_EXT)
+    REPORT_ERROR_AND_EXIT("Problem with OpenGL framebuffer after specifying depth render buffer.");
+
+  return ctx;
+}
+
+bool teardown_offscreen_context(OffscreenContext *ctx)
+{
+  // "un"bind my FBO
+  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
+
+  /*
+   * Cleanup
+   */
+  return true;
+}
+
+void write_targa(const char *filename, GLubyte *pixels, int width, int height)
+{
+	FILE *f = fopen( filename, "w" );
+	int y;
+	if (f) {
+		GLubyte header[] = {
+			00,00,02, 00,00,00, 00,00,00, 00,00,00,
+			0xff & width, 0xff & width >> 8,
+			0xff & height, 0xff & height >> 8,
+			32, 0x20 }; // next-to-last = bit depth
+		fwrite( header, sizeof(header), 1, f);
+		for (y=height-1; y>=0; y--)
+			fwrite( pixels + y*width*4, 4, width, f);
+		fclose(f);
+	}
+}
+
+bool save_framebuffer(OffscreenContext *ctx, const char *filename)
+{
+  /*
+   * Extract the resulting rendering as an image
+   */
+
+  int samplesPerPixel = 4; // R, G, B and A
+
+  GLubyte pixels[ ctx->width * ctx->height * samplesPerPixel ];
+  glReadPixels(0, 0, ctx->width, ctx->height, GL_BGRA, GL_UNSIGNED_BYTE, pixels);
+  printf("writing %s\n",filename);
+  write_targa(filename,pixels,ctx->width, ctx->height);
+
+  return true;
+}
+
+void bind_offscreen_context(OffscreenContext *ctx)
+{
+  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, ctx->fbo);
+}