OpenGL学习二十二：纹理坐标自动生成

可以让OpenGL自动生成纹理坐标，而不是使用glTexCoord*()函数显示地分配纹理坐标
void glTexGeni (GLenum coord, GLenum pname, GLint param);

 

 

coord	pname	param
{GL_S,GL_T}或{GL_R,GL_Q}	GL_TEXTURE_GEN_MODE	GL_OBJECT_LINEAR GL_EYE_LINEAR GL_SPHERE_MAP GL_NORMAL_MAP GL_REFLECTION_MAP
	GL_OBJECT_PLANE	浮点型数值
	GL_EYE_PLANE	浮点型数值

 

GL_OBJECT_LINEAR：物体模式，纹理会跟随物体的转动而转动（左图）
GL_EYE_LINEAR：视觉模式，纹理部会跟随物体的转动而转动，始终保持原状（右图）

         

 

GL_SPHERE_MAP：环境纹理（球体贴图）具有很好的反射效果
GL_REFLECTION_MAP:环境纹理（反射纹理）可替换GL_SPHERE_MAP
GL_NORMAL_MAP：常用于立方体贴图，或者散射与反射的场景

 

              

      GL_NORMAL_MAP球体贴图                          GL_REFLECTION_MAP球体贴图

 

纹理贴图做法
1设置纹理环绕模式
 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
2.设置纹理生成模式
 glTexGeni(GL_S,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
 glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
3.启用自动生成纹理
 glEnable(GL_TEXTURE_GEN_S);
 glEnable(GL_TEXTURE_GEN_T);

 

立方图纹理
立方图纹理是一种比较特殊的纹理技术，它用6幅二维图像构成一个以原点为中心的纹理立方体，对于每个片段，纹理坐标（S,T,R）被当做方向向量看待，每个纹理单元都表示从原点所看到的纹理立方体上的图像
可以调用glTexImage2D函数6次，分别使用他target参数表示立方体的各个面（+X,-X,+Y,-Y,+Z,-Z）从而创建一个立方体

glTexParameteri(GL_TEXTURE_CUBE_MAP_EXT, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X_EXT, 0, GL_RGBA, imageSize,
imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image1);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X_EXT, 0, GL_RGBA, imageSize,
imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image4);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y_EXT, 0, GL_RGBA, imageSize,
imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image2);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y_EXT, 0, GL_RGBA, imageSize,
imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image5);
glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z_EXT, 0, GL_RGBA, imageSize,
imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image3);
glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z_EXT, 0, GL_RGBA, imageSize,
imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image6);
glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_NORMAL_MAP_EXT);
glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_NORMAL_MAP_EXT);
glTexGeni(GL_R, GL_TEXTURE_GEN_MODE, GL_NORMAL_MAP_EXT);

 

 

#include "header.h"
#define	stripeImageWidth 16
#define	checkImageWidth 16
#define	checkImageHeight 16
#define	imageSize 4
static GLubyte image1[imageSize][imageSize][4];
static GLubyte image2[imageSize][imageSize][4];
static GLubyte image3[imageSize][imageSize][4];
static GLubyte image4[imageSize][imageSize][4];
static GLubyte image5[imageSize][imageSize][4];
static GLubyte image6[imageSize][imageSize][4];
static GLubyte checkImage[checkImageWidth][checkImageHeight][4];
static GLubyte stripeImage[4*stripeImageWidth];
static GLuint texName;


static GLfloat xequalzero[] = {1.0, 0.0, 0.0, 0.0};
static GLfloat slanted[] = {1.0, 1.0, 1.0, 0.0};
static GLfloat *currentCoeff;
static GLenum currentPlane;
static GLint currentGenMode;
double angle=0.0;

enum Shape
{
	CUBE,
	SPHERE,
	TEAPOT,
	CONE
}shape;
shape=TEAPOT;
void makeImage()
{
	int i,j,c;
	for ( i=0;i<checkImageWidth;i++)
	{
		for (j = 0; j < checkImageHeight; j++)
		{
			if(j%4==0)
			{
				checkImage[i][j][0]=0;
				checkImage[i][j][1]=255;
				checkImage[i][j][2]=0;
				checkImage[i][j][3]=255;;
				j++;
				if(j>=checkImageHeight)
				{
					break;
				}
				checkImage[i][j][0]=0;
				checkImage[i][j][1]=255;
				checkImage[i][j][2]=0;
				checkImage[i][j][3]=255;;

			}else
			{
				checkImage[i][j][0]=255;
				checkImage[i][j][1]=0;
				checkImage[i][j][2]=0;
				checkImage[i][j][3]=255;
			}

		}
	}
	for (i = 0; i < imageSize; i++) {
		for (j = 0; j < imageSize; j++) {
			//c = ((((i&0x1)==0)^((j&0x1))==0))*255;
			image1[i][j][0] = (GLubyte) 255;
			image1[i][j][1] = (GLubyte) 0;
			image1[i][j][2] = (GLubyte) 0;
			image1[i][j][3] = (GLubyte) 255;

			image2[i][j][0] = (GLubyte) 0;
			image2[i][j][1] = (GLubyte) 255;
			image2[i][j][2] = (GLubyte) 0;
			image2[i][j][3] = (GLubyte) 255;

			image3[i][j][0] = (GLubyte) 0;
			image3[i][j][1] = (GLubyte) 0;
			image3[i][j][2] = (GLubyte) 255;
			image3[i][j][3] = (GLubyte) 255;

			image4[i][j][0] = (GLubyte) 255;
			image4[i][j][1] = (GLubyte) 255;
			image4[i][j][2] = (GLubyte) 0;
			image4[i][j][3] = (GLubyte) 255;

			image5[i][j][0] = (GLubyte) 255;
			image5[i][j][1] = (GLubyte) 0;
			image5[i][j][2] = (GLubyte) 255;
			image5[i][j][3] = (GLubyte) 255;

			image6[i][j][0] = (GLubyte) 0;
			image6[i][j][1] = (GLubyte) 255;
			image6[i][j][2] = (GLubyte) 255;
			image6[i][j][3] = (GLubyte) 255;
		}
	}
}

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();


		//glRotated(-90,1,0,0);
	glRotated(angle,0,1,1);


	glDisable(GL_TEXTURE_2D);
	glDisable(GL_TEXTURE_CUBE_MAP_EXT);
	glBindTexture(GL_TEXTURE_2D,texName);
	if(shape==TEAPOT)
	{
		glEnable(GL_TEXTURE_2D);  
		glutSolidTeapot(100);
	}else if(shape==SPHERE)
	{
		glEnable(GL_TEXTURE_2D);  
		glutSolidSphere(100,50,32);
	}else if(shape==CUBE)
	{
		glEnable(GL_TEXTURE_CUBE_MAP_EXT);  
		glutSolidCube(100);
	
	}else if(shape==CONE)
	{
		glEnable(GL_TEXTURE_2D); 
		glutWireCone(200,200,16,16);

	}
	glutSwapBuffers();
	glFlush();

}

void init()
{
	makeImage();
	glClearColor(0,0,0,0);
	glClearDepth(1.0);
	
	glEnable(GL_DEPTH_TEST);					
	glDepthFunc(GL_LEQUAL);	
	glShadeModel(GL_SMOOTH);

	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

	glEnable(GL_TEXTURE_GEN_S);
	glEnable(GL_TEXTURE_GEN_T);

	glEnable(GL_LIGHTING);
	glEnable(GL_LIGHT0);

	glGenTextures(1,&texName);
	glBindTexture(GL_TEXTURE_2D,texName);

	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, checkImageWidth, checkImageHeight,0,GL_RGBA, GL_UNSIGNED_BYTE, checkImage);
	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_MIN_FILTER,GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
	glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
	glTexGeni(GL_S,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
	glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);





}
void reshape(int w, int h)
{
	glViewport(0, 0, (GLsizei) w, (GLsizei) h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	glOrtho(-400,400,-300,300,-1000,1000);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

void keyboard(unsigned char key,int x,int y)
{
	switch (key)
	{
	case 't':
		shape=TEAPOT;
		//glTexGeni(GL_S,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
		//glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);
		glutPostRedisplay();
		break;
	case 's':
		shape=SPHERE;
		glTexGeni(GL_S,GL_TEXTURE_GEN_MODE,GL_SPHERE_MAP);
		glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_SPHERE_MAP);
		glutPostRedisplay();
		break;
	case 'c':
		shape=CUBE;


		glTexParameteri(GL_TEXTURE_CUBE_MAP_EXT, GL_TEXTURE_WRAP_S, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_CUBE_MAP_EXT, GL_TEXTURE_WRAP_T, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_CUBE_MAP_EXT, GL_TEXTURE_WRAP_R, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_CUBE_MAP_EXT, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
		glTexParameteri(GL_TEXTURE_CUBE_MAP_EXT, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
		glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X_EXT, 0, GL_RGBA, imageSize, 
			imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image1);
		glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X_EXT, 0, GL_RGBA, imageSize, 
			imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image4);
		glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y_EXT, 0, GL_RGBA, imageSize,
			imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image2);
		glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y_EXT, 0, GL_RGBA, imageSize,
			imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image5);
		glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z_EXT, 0, GL_RGBA, imageSize,
			imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image3);
		glTexImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z_EXT, 0, GL_RGBA, imageSize,
			imageSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, image6);
		glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_NORMAL_MAP_EXT);
		glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_NORMAL_MAP_EXT);
		glTexGeni(GL_R, GL_TEXTURE_GEN_MODE, GL_NORMAL_MAP_EXT); 
		glEnable(GL_TEXTURE_GEN_S);
		glEnable(GL_TEXTURE_GEN_T);
		glEnable(GL_TEXTURE_GEN_R);

		//glTexGeni(GL_S,GL_TEXTURE_GEN_MODE,GL_SPHERE_MAP);
		//glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_SPHERE_MAP);

	
		glutPostRedisplay();
		break;
	case 'n':

		shape=CONE;
		//glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR);

		//glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);

		glutPostRedisplay();
		break;
	case 'e':
		glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);

		glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_EYE_LINEAR);

		glutPostRedisplay();
		break;
	case 'o':
		glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR);

		glTexGeni(GL_T,GL_TEXTURE_GEN_MODE,GL_OBJECT_LINEAR);

		glutPostRedisplay();
		break;
	}
	

}
void rotate()
{
	angle+=0.1;
	glutPostRedisplay();
}
void mouse(int button,int state,int x,int y)
{ 
	switch(button)
	{
	  case GLUT_LEFT_BUTTON:
		  if(GLUT_DOWN==state)
		  {
			  glutIdleFunc(rotate);
		  }
		  break;
	  case GLUT_RIGHT_BUTTON:
		  if(GLUT_DOWN==state)
		  {
			  glutIdleFunc(0);
		  }
		  break;
	}
}

int main(int argc,char **argv)
{
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB|GLUT_DEPTH);
	glutInitWindowSize(800,600);
	glutInitWindowPosition(100,100);
	glutCreateWindow("纹理坐标自动生成");
	glewInit();
	init();
	glutDisplayFunc(display);
	glutKeyboardFunc(keyboard);
    glutReshapeFunc(reshape);
 	glutMouseFunc(mouse);
	glutMainLoop();
}