From 83054d9297d12dbd7bd7c86a6bed6a5fc63debdc Mon Sep 17 00:00:00 2001
From: Brian Paul <brian.paul@tungstengraphics.com>
Date: Fri, 5 Sep 2008 13:07:43 -0600
Subject: [PATCH] press 'c' to toggle Z clear value between 0/1

---
 progs/trivial/tri-z.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/progs/trivial/tri-z.c b/progs/trivial/tri-z.c
index c8296a9..335d2b9 100644
--- a/progs/trivial/tri-z.c
+++ b/progs/trivial/tri-z.c
@@ -56,6 +56,15 @@ static struct { GLenum func; const char *str; } funcs[] =
 #define NUM_FUNCS (sizeof(funcs) / sizeof(funcs[0]))
 
 static int curFunc = 0;
+static double clearVal = 1.0;
+
+
+static void usage(void)
+{
+   printf("t - toggle rendering order of triangles\n");
+   printf("c - toggle Z clear value between 0, 1\n");
+   printf("f - cycle through depth test functions\n");
+}
 
 
 static void init(void)
@@ -88,11 +97,13 @@ static void drawRightTriangle(void)
 
 void display(void)
 {
-   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
-
-   printf("GL_DEPTH_FUNC = %s\n", funcs[curFunc].str);
+   printf("GL_CLEAR_DEPTH = %f  GL_DEPTH_FUNC = %s\n",
+          clearVal, funcs[curFunc].str);
+   glClearDepth(clearVal);
    glDepthFunc(funcs[curFunc].func);
 
+   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
    if (leftFirst) {
       drawLeftTriangle();
       drawRightTriangle();
@@ -120,6 +131,11 @@ void reshape(int w, int h)
 void keyboard(unsigned char key, int x, int y)
 {
    switch (key) {
+      case 'c':
+      case 'C':
+         clearVal = 1.0 - clearVal;
+         glutPostRedisplay();	
+         break;
       case 'f':
       case 'F':
          curFunc = (curFunc + 1) % NUM_FUNCS;
@@ -148,10 +164,11 @@ int main(int argc, char** argv)
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize (200, 200);
    glutCreateWindow (argv[0]);
-   init();
    glutReshapeFunc (reshape);
    glutKeyboardFunc (keyboard);
    glutDisplayFunc (display);
+   init();
+   usage();
    glutMainLoop();
    return 0;
 }
-- 
2.7.4