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

opengl学习笔记(三):经过纹理贴图的棋盘

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。

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