1 files changed, 207 insertions, 0 deletions
diff --git a/progs/trivial/clear-fbo.c b/progs/trivial/clear-fbo.c
new file mode 100644
index 0000000000..64b25430c6
--- /dev/null
+++ b/progs/trivial/clear-fbo.c
@@ -0,0 +1,207 @@
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <string.h>
+
+#include <GL/glew.h>
+#include <GL/glut.h>
+
+
+
+static int Width = 512, Height = 512;
+static GLuint MyFB, MyRB;
+
+
+#define CheckError() assert(glGetError() == 0)
+
+GLenum doubleBuffer;
+
+static void Init(void)
+{
+   fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
+   fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
+   fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
+
+
+   if (!glutExtensionSupported("GL_EXT_framebuffer_object")) {
+      printf("GL_EXT_framebuffer_object not found!\n");
+      exit(0);
+   }
+
+
+   glGenFramebuffersEXT(1, &MyFB);
+   glGenRenderbuffersEXT(1, &MyRB);
+
+   {
+      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
+
+      glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, MyRB);
+
+      glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT1_EXT,
+				   GL_RENDERBUFFER_EXT, MyRB);
+
+      glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
+
+      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
+   }
+
+}
+
+
+
+static void
+Reshape( int width, int height )
+{
+   glViewport( 0, 0, width, height );
+   glMatrixMode( GL_PROJECTION );
+   glLoadIdentity();
+   glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
+   glMatrixMode( GL_MODELVIEW );
+
+   Width = width;
+   Height = height;
+   glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_RGB, Width, Height);
+}
+
+static void Key(unsigned char key, int x, int y)
+{
+
+    switch (key) {
+      case 27:
+	exit(1);
+      default:
+	return;
+    }
+
+    glutPostRedisplay();
+}
+
+
+
+static void Draw( void )
+{
+
+   /* draw to user framebuffer */
+   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
+   glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT);
+   glReadBuffer(GL_COLOR_ATTACHMENT1_EXT);
+
+   
+   glViewport(0, 0, Width, Height);
+   CheckError();
+
+   glClearColor(0.5, 0.5, 1.0, 0.0);
+   glClear(GL_COLOR_BUFFER_BIT);
+   CheckError();
+
+   if (0) {
+      glBegin(GL_TRIANGLES);
+      glColor3f(0,0,.7); 
+      glVertex3f( 0.9, -0.9, -30.0);
+      glColor3f(.8,0,0); 
+      glVertex3f( 0.9,  0.9, -30.0);
+      glColor3f(0,.9,0); 
+      glVertex3f(-0.9,  0.0, -30.0);
+      glEnd();
+   }
+
+   {
+      GLubyte *buffer = malloc(Width * Height * 4);
+
+      /* read from user framebuffer */
+      glReadPixels(0, 0, Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
+      CheckError();
+
+      /* draw to window */
+      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
+      glViewport(0, 0, Width, Height);
+
+      /* Try to clear the window, but will overwrite:
+       */
+      glClearColor(0.8, 0.8, 0, 0.0);
+      glClear(GL_COLOR_BUFFER_BIT);
+
+      glWindowPos2iARB(30, 30);
+      glDrawPixels(Width-60, Height-60, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
+      
+      free(buffer);
+   }
+   
+   /* Bind normal framebuffer */
+   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
+   glViewport(0, 0, Width, Height);
+
+   if (0) {
+      glBegin(GL_TRIANGLES);
+      glColor3f(0,.7,0); 
+      glVertex3f( 0.5, -0.5, -30.0);
+      glColor3f(0,0,.8); 
+      glVertex3f( 0.5,  0.5, -30.0);
+      glColor3f(.9,0,0); 
+      glVertex3f(-0.5,  0.0, -30.0);
+      glEnd();
+   }
+
+   if (doubleBuffer)
+      glutSwapBuffers();
+   else
+      glFinish();
+
+   CheckError();
+}
+
+
+static GLenum Args(int argc, char **argv)
+{
+    GLint i;
+
+    doubleBuffer = GL_FALSE;
+
+    for (i = 1; i < argc; i++) {
+        if (strcmp(argv[i], "-sb") == 0) {
+	    doubleBuffer = GL_FALSE;
+	} else if (strcmp(argv[i], "-db") == 0) {
+	    doubleBuffer = GL_TRUE;
+	} else {
+	    fprintf(stderr, "%s (Bad option).\n", argv[i]);
+	    return GL_FALSE;
+	}
+    }
+    return GL_TRUE;
+}
+
+
+
+int
+main( int argc, char *argv[] )
+{
+    GLenum type;
+
+    glutInit(&argc, argv);
+
+    if (Args(argc, argv) == GL_FALSE) {
+	exit(1);
+    }
+
+    glutInitWindowPosition(100, 0); glutInitWindowSize( Width, Height );
+
+    type = GLUT_RGB;
+    type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
+    glutInitDisplayMode(type);
+
+    if (glutCreateWindow(argv[0]) == GL_FALSE) {
+	exit(1);
+    }
+
+    glewInit();
+
+    Init();
+
+    glutReshapeFunc(Reshape);
+    glutKeyboardFunc(Key);
+    glutDisplayFunc(Draw);
+    glutMainLoop();
+    return 0;
+}