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-rw-r--r--progs/demos/cubemap.c51
1 files changed, 45 insertions, 6 deletions
diff --git a/progs/demos/cubemap.c b/progs/demos/cubemap.c
index ef5d235550..b3bdd64f68 100644
--- a/progs/demos/cubemap.c
+++ b/progs/demos/cubemap.c
@@ -47,6 +47,8 @@ static GLfloat Xrot = 0, Yrot = 0;
static GLfloat EyeDist = 10;
static GLboolean use_vertex_arrays = GL_FALSE;
static GLboolean anim = GL_TRUE;
+static GLboolean NoClear = GL_FALSE;
+static GLint FrameParity = 0;
#define eps1 0.99
#define br 20.0 /* box radius */
@@ -156,7 +158,30 @@ static void draw_skybox( void )
static void draw( void )
{
- glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+ if (NoClear) {
+ /* This demonstrates how we can avoid calling glClear.
+ * This method only works if every pixel in the window is painted for
+ * every frame.
+ * We can simply skip clearing of the color buffer in this case.
+ * For the depth buffer, we alternately use a different subrange of
+ * the depth buffer for each frame. For the odd frame use the range
+ * [0, 0.5] with GL_LESS. For the even frames, use the range [1, 0.5]
+ * with GL_GREATER.
+ */
+ FrameParity = 1 - FrameParity;
+ if (FrameParity) {
+ glDepthRange(0.0, 0.5);
+ glDepthFunc(GL_LESS);
+ }
+ else {
+ glDepthRange(1.0, 0.5);
+ glDepthFunc(GL_GREATER);
+ }
+ }
+ else {
+ /* ordinary clearing */
+ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+ }
glPushMatrix(); /*MODELVIEW*/
glTranslatef( 0.0, 0.0, -EyeDist );
@@ -452,6 +477,24 @@ static void usage(void)
}
+static void parse_args(int argc, char *argv[])
+{
+ int initFlag = 0;
+ int i;
+
+ for (i = 1; i < argc; i++) {
+ if (strcmp(argv[i], "-i") == 0)
+ initFlag = 1;
+ else if (strcmp(argv[i], "--noclear") == 0)
+ NoClear = GL_TRUE;
+ else {
+ fprintf(stderr, "Bad option: %s\n", argv[i]);
+ exit(1);
+ }
+ }
+ init (initFlag);
+}
+
int main( int argc, char *argv[] )
{
glutInit(&argc, argv);
@@ -459,17 +502,13 @@ int main( int argc, char *argv[] )
glutInitWindowSize(600, 500);
glutInitDisplayMode( GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE );
glutCreateWindow("Texture Cube Mapping");
-
- if (argc > 1 && strcmp(argv[1] , "-i") == 0)
- init( 1 );
- else
- init( 0 );
glutReshapeFunc( reshape );
glutKeyboardFunc( key );
glutSpecialFunc( specialkey );
glutDisplayFunc( draw );
if (anim)
glutIdleFunc(idle);
+ parse_args(argc, argv);
usage();
glutMainLoop();
return 0;