progs/trivial: added clear-fbo-scissor.c to test scissored clear of FBO

progs/trivial/Makefile

@@ -11,6 +11,7 @@ include $(TOP)/configs/current
 LIBS = -L$(TOP)/$(LIB_DIR) -l $(GLEW_LIB) -l$(GLUT_LIB) -l$(GLU_LIB) -l$(GL_LIB) $(APP_LIB_DEPS)
 
 SOURCES = \
+	clear-fbo-scissor.c \
 	clear-fbo-tex.c \
 	clear-fbo.c \
 	clear-scissor.c \

progs/trivial/SConscript

@@ -1,7 +1,8 @@
 Import('*')
 
 progs = [
-    'clear-fbo-tex',
+	'clear-fbo-scissor',
+	'clear-fbo-tex',
 	'clear-fbo',
 	'clear-scissor',
 	'clear-undefined',

progs/trivial/clear-fbo-scissor.c

@@ -0,0 +1,186 @@
+/*
+ * Use scissor to clear the four quadrants of the FBO to different
+ * colors.  Then draw a grey triangle in the middle.
+ */
+
+
+#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)
+
+
+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));
+   fflush(stderr);
+
+   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_ATTACHMENT0_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, -1.0, 1.0);
+   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)
+{
+   if (key == 27) {
+      exit(0);
+   }
+   glutPostRedisplay();
+}
+
+
+static void
+Draw(void)
+{
+   GLboolean scissor = GL_TRUE;
+   GLboolean copyPix = GL_FALSE;
+
+   /* draw to user framebuffer */
+   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, MyFB);
+   glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT);
+   glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
+
+   glViewport(0, 0, Width, Height);
+   CheckError();
+
+   if (scissor) {
+      glEnable(GL_SCISSOR_TEST);
+
+      /* lower-left = red */
+      glClearColor(1, 0, 0, 0);
+      glScissor(0, 0, Width / 2, Height / 2);
+      glClear(GL_COLOR_BUFFER_BIT); 
+
+      /* lower-right = green */
+      glClearColor(0, 1, 0, 0);
+      glScissor(Width / 2, 0, Width - Width / 2, Height / 2);
+      glClear(GL_COLOR_BUFFER_BIT); 
+
+      /* upper-left = blue */
+      glClearColor(0, 0, 1, 0);
+      glScissor(0, Height / 2, Width / 2, Height - Height / 2);
+      glClear(GL_COLOR_BUFFER_BIT); 
+
+      /* upper-right = white */
+      glClearColor(1, 1, 1, 0);
+      glScissor(Width / 2, Height / 2, Width - Width / 2, Height - Height / 2);
+      glClear(GL_COLOR_BUFFER_BIT); 
+
+      glDisable(GL_SCISSOR_TEST);
+   }
+   else {
+      glClearColor(0, 1, 0, 0);
+      glClear(GL_COLOR_BUFFER_BIT);
+   }
+
+   /* gray triangle in middle, pointing up */
+   glColor3f(0.5, 0.5, 0.5);
+   glBegin(GL_TRIANGLES);
+   glVertex2f(Width/4, Height/4);
+   glVertex2f(Width*3/4, Height/4);
+   glVertex2f(Width/2, Height*3/4);
+   glVertex2f(-0.5, -0.5);
+   glVertex2f(+0.5, -0.5);
+   glVertex2f( 0.0, 0.7);
+   glEnd();
+
+   CheckError();
+
+   /* copy fbo to window */
+   glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, MyFB);
+   glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
+   glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, 0);
+   glDrawBuffer(GL_BACK);
+   
+   if (copyPix) {
+      glWindowPos2i(0, 0);
+      glCopyPixels(0, 0, Width, Height, GL_COLOR);
+   }
+   else {
+      GLubyte *buffer = malloc(Width * Height * 4);
+
+      /* read from user framebuffer */
+      glReadPixels(0, 0, Width, Height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
+
+      /* draw to window */
+      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
+      glWindowPos2iARB(0, 0);
+      glDrawPixels(Width, Height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
+
+      free(buffer);
+   }
+
+   /* Bind normal framebuffer */
+   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
+
+   glutSwapBuffers();
+
+   CheckError();
+}
+
+
+int
+main(int argc, char *argv[])
+{
+   glutInit(&argc, argv);
+   glutInitWindowPosition(100, 0);
+   glutInitWindowSize(Width, Height);
+   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
+
+   if (!glutCreateWindow(argv[0])) {
+      exit(1);
+   }
+
+   glewInit();
+   Init();
+   glutReshapeFunc(Reshape);
+   glutKeyboardFunc(Key);
+   glutDisplayFunc(Draw);
+   glutMainLoop();
+   return 0;
+}