绘制图形与3D增强技巧(四)----多边形图元及其点画模式

1.四边形图元

glBegin(GL_QUADS);

glend();

2.通用多边形

glBegin(GL_POLYGONS);

glend();

3.多边形点画模式

glenable(GL_POLYGON_STIPPLE);

glPolygonStipple(pBitmp);

其中pBitmap为一块指定了数据区域的指针，

#include "stdafx.h"

// PStipple.cpp
// OpenGL SuperBible
// Demonstrates OpenGL Polygon Stippling
// Program by Richard S. Wright Jr.
#include<GLglut.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[128] = { 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;
}