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/*
* Test glRead/DrawPixels for GL_STENCIL_INDEX, with pixelzoom.
*
* Brian Paul
* 8 April 2010
*/
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glew.h>
#include <GL/glut.h>
static GLint WinWidth = 500, WinHeight = 500;
static GLboolean TestPacking = GL_FALSE;
static GLboolean TestList = GL_FALSE;
static GLuint StencilValue = 192;
static void Display(void)
{
GLubyte stencil[100 * 100 * 2];
GLubyte stencil2[400 * 400]; /* *2 to test pixelstore stuff */
GLuint list;
glClearColor(0.5, 0.5, 0.5, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glStencilOp(GL_INVERT, GL_KEEP, GL_REPLACE);
glStencilFunc(GL_ALWAYS, StencilValue, ~0);
glEnable(GL_STENCIL_TEST);
/* draw a sphere */
glViewport(0, 0, 100, 100);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1, 1, -1, 1, -1, 0); /* clip away back half of sphere */
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glutSolidSphere(1.0, 20, 10);
glDisable(GL_STENCIL_TEST);
if (TestPacking) {
glPixelStorei(GL_PACK_ROW_LENGTH, 120);
glPixelStorei(GL_PACK_SKIP_PIXELS, 5);
}
/* read the stencil image */
glReadPixels(0, 0, 100, 100, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, stencil);
{
GLubyte min, max;
int i;
min = max = stencil[0];
for (i = 1; i < 100 * 100; i++) {
if (stencil[i] < min)
min = stencil[i];
if (stencil[i] > max)
max = stencil[i];
}
printf("Stencil value range: [%u, %u]\n", min, max);
if (max != StencilValue) {
printf("Error: expected max stencil val of %u, found %u\n",
StencilValue, max);
}
}
/* Draw the Z image as luminance above original rendering */
glWindowPos2i(0, 100);
glDrawPixels(100, 100, GL_LUMINANCE, GL_UNSIGNED_BYTE, stencil);
if (1) {
if (TestPacking) {
glPixelStorei(GL_PACK_ROW_LENGTH, 0);
glPixelStorei(GL_PACK_SKIP_PIXELS, 0);
glPixelStorei(GL_UNPACK_ROW_LENGTH, 120);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 5);
}
/* draw stencil image with scaling (into stencil buffer) */
glPixelZoom(4.0, 4.0);
glColor4f(1, 0, 0, 0);
glWindowPos2i(100, 0);
if (TestList) {
list = glGenLists(1);
glNewList(list, GL_COMPILE);
glDrawPixels(100, 100, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, stencil);
glEndList();
glCallList(list);
glDeleteLists(list, 1);
}
else {
glDrawPixels(100, 100, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, stencil);
}
if (TestPacking) {
glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
}
/* read back scaled stencil image */
glReadPixels(100, 0, 400, 400, GL_STENCIL_INDEX,
GL_UNSIGNED_BYTE, stencil2);
/* draw as luminance */
glPixelZoom(1.0, 1.0);
glWindowPos2i(100, 0);
glDrawPixels(400, 400, GL_LUMINANCE, GL_UNSIGNED_BYTE, stencil2);
}
glutSwapBuffers();
}
static void Reshape(int width, int height)
{
WinWidth = width;
WinHeight = height;
glViewport(0, 0, width, height);
}
static void Key(unsigned char key, int x, int y)
{
(void) x;
(void) y;
switch (key) {
case 'p':
TestPacking = !TestPacking;
printf("Test pixel pack/unpack: %d\n", TestPacking);
break;
case 'l':
TestList = !TestList;
printf("Test dlist: %d\n", TestList);
break;
case 27:
exit(0);
break;
}
glutPostRedisplay();
}
static void Init(void)
{
const GLfloat blue[4] = {.1, .1, 1.0, 1.0};
const GLfloat gray[4] = {0.2, 0.2, 0.2, 1.0};
const GLfloat white[4] = {1.0, 1.0, 1.0, 1.0};
const GLfloat pos[4] = {0, 0, 10, 0};
GLint bits;
printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
glGetIntegerv(GL_STENCIL_BITS, &bits);
printf("Stencil bits: %d\n", bits);
assert(bits >= 8);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, blue);
glLightfv(GL_LIGHT0, GL_AMBIENT, gray);
glLightfv(GL_LIGHT0, GL_DIFFUSE, white);
glLightfv(GL_LIGHT0, GL_POSITION, pos);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
}
int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowPosition(0, 0);
glutInitWindowSize(WinWidth, WinHeight);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_STENCIL | GLUT_DOUBLE);
glutCreateWindow(argv[0]);
glewInit();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Display);
Init();
glutMainLoop();
return 0;
}
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