this code is from the OpenGL SuperBible and i was wondering what the hell this line stipple code like “0x00” means and how it works… thanx,
Y-T
// PStipple.c
// OpenGL SuperBible, Chapter 4
// Demonstrates OpenGL Polygon Stippling
// Program by Richard S. Wright Jr.
#include <windows.h>
#include <gl/gl.h>
#include <gl/glu.h>
#include <gl/glut.h>
#include <math.h>
// Define a constant for the value of PI
#define GL_PI 3.1415f
// Rotation amounts
static GLfloat xRot = 0.0f;
static GLfloat yRot = 0.0f;
// Bitmap of camp fire
GLubyte fire[] = { 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0xc0,
0x00, 0x00, 0x01, 0xf0,
0x00, 0x00, 0x07, 0xf0,
0x0f, 0x00, 0x1f, 0xe0,
0x1f, 0x80, 0x1f, 0xc0,
0x0f, 0xc0, 0x3f, 0x80,
0x07, 0xe0, 0x7e, 0x00,
0x03, 0xf0, 0xff, 0x80,
0x03, 0xf5, 0xff, 0xe0,
0x07, 0xfd, 0xff, 0xf8,
0x1f, 0xfc, 0xff, 0xe8,
0xff, 0xe3, 0xbf, 0x70,
0xde, 0x80, 0xb7, 0x00,
0x71, 0x10, 0x4a, 0x80,
0x03, 0x10, 0x4e, 0x40,
0x02, 0x88, 0x8c, 0x20,
0x05, 0x05, 0x04, 0x40,
0x02, 0x82, 0x14, 0x40,
0x02, 0x40, 0x10, 0x80,
0x02, 0x64, 0x1a, 0x80,
0x00, 0x92, 0x29, 0x00,
0x00, 0xb0, 0x48, 0x00,
0x00, 0xc8, 0x90, 0x00,
0x00, 0x85, 0x10, 0x00,
0x00, 0x03, 0x00, 0x00,
0x00, 0x00, 0x10, 0x00 };
// Called to draw scene
void RenderScene(void)
{
// Clear the window
glClear(GL_COLOR_BUFFER_BIT);
// Save matrix state and do the rotation
glPushMatrix();
glRotatef(xRot, 1.0f, 0.0f, 0.0f);
glRotatef(yRot, 0.0f, 1.0f, 0.0f);
// Begin the stop sign shape,
// use a standard polygon for simplicity
glBegin(GL_POLYGON);
glVertex2f(-20.0f, 50.0f);
glVertex2f(20.0f, 50.0f);
glVertex2f(50.0f, 20.0f);
glVertex2f(50.0f, -20.0f);
glVertex2f(20.0f, -50.0f);
glVertex2f(-20.0f, -50.0f);
glVertex2f(-50.0f, -20.0f);
glVertex2f(-50.0f, 20.0f);
glEnd();
// Restore transformations
glPopMatrix();
// Flush drawing commands
glutSwapBuffers();
}
// This function does any needed initialization on the rendering
// context.
void SetupRC()
{
// Black background
glClearColor(0.0f, 0.0f, 0.0f, 1.0f );
// Set drawing color to red
glColor3f(1.0f, 0.0f, 0.0f);
// Enable polygon stippling
glEnable(GL_POLYGON_STIPPLE);
// Specify a specific stipple pattern
glPolygonStipple(fire);
}
void SpecialKeys(int key, int x, int y)
{
if(key == GLUT_KEY_UP)
xRot-= 5.0f;
if(key == GLUT_KEY_DOWN)
xRot += 5.0f;
if(key == GLUT_KEY_LEFT)
yRot -= 5.0f;
if(key == GLUT_KEY_RIGHT)
yRot += 5.0f;
if(key > 356.0f)
xRot = 0.0f;
if(key < -1.0f)
xRot = 355.0f;
if(key > 356.0f)
yRot = 0.0f;
if(key < -1.0f)
yRot = 355.0f;
// Refresh the Window
glutPostRedisplay();
}
void ChangeSize(int w, int h)
{
GLfloat nRange = 100.0f;
// Prevent a divide by zero
if(h == 0)
h = 1;
// Set Viewport to window dimensions
glViewport(0, 0, w, h);
// Reset projection matrix stack
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// Establish clipping volume (left, right, bottom, top, near, far)
if (w <= h)
glOrtho (-nRange, nRange, -nRange*h/w, nRange*h/w, -nRange, nRange);
else
glOrtho (-nRange*w/h, nRange*w/h, -nRange, nRange, -nRange, nRange);
// Reset Model view matrix stack
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutCreateWindow(“Polygon Stippling”);
glutReshapeFunc(ChangeSize);
glutSpecialFunc(SpecialKeys);
glutDisplayFunc(RenderScene);
SetupRC();
glutMainLoop();
return 0;
}