opengl学习笔记（三）:经过纹理贴图的棋盘

opengl纹理贴图的步骤：

1：创建纹理对象，并为它指定一个纹理

2：确定纹理如何应用到每个像素上

3：启用纹理贴图功能

4：绘制场景，提供纹理坐标和几何图形坐标

注意：纹理坐标必须在RGBA模式下才能使用。

使用一个简单的程序演示纹理贴图，纹理（由交替的黑白方块组成）是有程序产生的。

/*Create checkerboard texture */

#include <GL/glut.h>

#include <GL/gl.h>

#include <GL/glu.h>

#define checkImageWidth 64

#define checkImageHeight 64

static GLubyte checkImage [checkImageHeight][checkImageWidth][];

static GLuint texName;

void makeCheckImage(void)

{

    int i,j,c;

    for (i = ; i < checkImageHeight; i++)

    {

        for (j = ; j < checkImageWidth; j++)

        {

            c = (((i&0x8)==)^((j&0x8))==)*;

            checkImage [i][j][] = (GLubyte)c;

            checkImage [i][j][] = (GLubyte)c;

            checkImage [i][j][] = (GLubyte)c;

            checkImage [i][j][] = (GLubyte);

        }

    }

}

void init(void)

{

    glClearColor(0.0,0.0,0.0,0.0);

    glShadeModel(GL_FLAT);

    glEnable(GL_DEPTH_TEST);

    makeCheckImage();

    glPixelStorei(GL_UNPACK_ALIGNMENT,);

    glGenTextures(,&texName);

    glBindTexture(GL_TEXTURE_2D,texName);

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_REPEAT);

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_REPEAT);

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);

    glTexImage2D(GL_TEXTURE_2D,,GL_RGBA,checkImageWidth,checkImageHeight,,GL_RGBA,GL_UNSIGNED_BYTE,checkImage);

}

void display(void)

{

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

    glEnable(GL_TEXTURE_2D);

    glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_REPLACE);

    glBindTexture(GL_TEXTURE_2D,texName);

    glBegin(GL_QUADS);

    glTexCoord2f(0.0,0.0);glVertex3f(-2.0,-1.0,0.0);

    glTexCoord2f(0.0,1.0);glVertex3f(-2.0,1.0,0.0);

    glTexCoord2f(1.0,1.0);glVertex3f(0.0,1.0,0.0);

    glTexCoord2f(1.0,0.0);glVertex3f(0.0,-1.0,0.0);

    glTexCoord2f(0.0,0.0);glVertex3f(0.0,-1.0,0.0);

    glTexCoord2f(0.0,1.0);glVertex3f(1.0,1.0,0.0);

    glTexCoord2f(1.0,1.0);glVertex3f(2.41421,1.0,-1.41421);

    glTexCoord2f(1.0,0.0);glVertex3f(2.41421,-1.0,-1.41421);

    glEnd();

    glFlush();

    glDisable(GL_TEXTURE_2D);

}

void reshape(int w, int h)

{

    glViewport(,,(GLsizei)w,(GLsizei)h);

    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();

    gluPerspective(60.0,(GLfloat)w/(GLfloat)h,1.0,30.0);

    glMatrixMode(GL_MODELVIEW);

    glLoadIdentity();

    glTranslatef(0.0,0.0,-3.6);

}

int main( int argc, char** argv )

{

    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);

    glutInitWindowPosition(, );

    glutInitWindowSize(, );

    glutCreateWindow(argv[]);

    init();

    glutDisplayFunc(display);

    glutReshapeFunc(reshape);

    glutMainLoop();

    return ;

}

程序运行结果

这个程序把这个纹理应用到两个正方形上，然后在透视投影模式下对它们进行渲染。其中一个正方形正面朝向观察者，另一个正方形与观察者呈45度倾斜，如图所示。

巴特西

opengl学习笔记（三）:经过纹理贴图的棋盘

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