OGL纹理之纹理过滤器和多级渐进纹理mipmap_gl_generate_mipmap_sgis

#include <stdlib.h>
#include <GL/glut.h>
 
GLubyte mipmapImage32[32][32][3];
GLubyte mipmapImage16[16][16][3];
GLubyte mipmapImage8[8][8][3];
GLubyte mipmapImage4[4][4][3];
GLubyte mipmapImage2[2][2][3];
GLubyte mipmapImage1[1][1][3];
 
void makeImages(void)
{
    int i, j;
    
    for (i = 0; i < 32; i++) {
	for (j = 0; j < 32; j++) {
	    mipmapImage32[i][j][0] = 255;
	    mipmapImage32[i][j][1] = 255;
	    mipmapImage32[i][j][2] = 0;
	}
    }
    for (i = 0; i < 16; i++) {
	for (j = 0; j < 16; j++) {
	    mipmapImage16[i][j][0] = 255;
	    mipmapImage16[i][j][1] = 0;
	    mipmapImage16[i][j][2] = 255;
	}
    }
    for (i = 0; i < 8; i++) {
	for (j = 0; j < 8; j++) {
	    mipmapImage8[i][j][0] = 255;
	    mipmapImage8[i][j][1] = 0;
	    mipmapImage8[i][j][2] = 0;
	}
    }
    for (i = 0; i < 4; i++) {
	for (j = 0; j < 4; j++) {
	    mipmapImage4[i][j][0] = 0;
	    mipmapImage4[i][j][1] = 255;
	    mipmapImage4[i][j][2] = 0;
	}
    }
    for (i = 0; i < 2; i++) {
	for (j = 0; j < 2; j++) {
	    mipmapImage2[i][j][0] = 0;
	    mipmapImage2[i][j][1] = 0;
	    mipmapImage2[i][j][2] = 255;
	}
    }
    mipmapImage1[0][0][0] = 255;
    mipmapImage1[0][0][1] = 255;
    mipmapImage1[0][0][2] = 255;
}
 
void myinit(void)
{    
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LESS);
    glShadeModel(GL_FLAT);
 
    glTranslatef(0.0, 0.0, -3.6);
    makeImages();
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexImage2D(GL_TEXTURE_2D, 0, 3, 32, 32, 0,
		 GL_RGB, GL_UNSIGNED_BYTE, &mipmapImage32[0][0][0]);
    glTexImage2D(GL_TEXTURE_2D, 1, 3, 16, 16, 0,
		 GL_RGB, GL_UNSIGNED_BYTE, &mipmapImage16[0][0][0]);
    glTexImage2D(GL_TEXTURE_2D, 2, 3, 8, 8, 0,
		 GL_RGB, GL_UNSIGNED_BYTE, &mipmapImage8[0][0][0]);
    glTexImage2D(GL_TEXTURE_2D, 3, 3, 4, 4, 0,
		 GL_RGB, GL_UNSIGNED_BYTE, &mipmapImage4[0][0][0]);
    glTexImage2D(GL_TEXTURE_2D, 4, 3, 2, 2, 0,
		 GL_RGB, GL_UNSIGNED_BYTE, &mipmapImage2[0][0][0]);
    glTexImage2D(GL_TEXTURE_2D, 5, 3, 1, 1, 0,
		 GL_RGB, GL_UNSIGNED_BYTE, &mipmapImage1[0][0][0]);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, 
	GL_NEAREST_MIPMAP_NEAREST);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
    glEnable(GL_TEXTURE_2D);
	//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);//GL_NEAREST最近点采样块有明显锯齿，GL_LINEAR线性过滤效果较好
	//GL_NEAREST最近点采样块有明显锯齿，GL_LINEAR双线性采样效果较好
	//#define GL_NEAREST_MIPMAP_NEAREST         0x2700 // 两个mipmap之间选择最近的纹理单元，采用最近点采样
	//#define GL_LINEAR_MIPMAP_NEAREST          0x2701 // 两个mipmap之间进行计算双线性采样后，选择最近点
	//#define GL_NEAREST_MIPMAP_LINEAR          0x2702 // 两个mipmap之间选择最近的纹理单元后，采用双线性采样
	//#define GL_LINEAR_MIPMAP_LINEAR           0x2703 // 两个mipmap之间进行计算双线性采样，两个结果再进行线性匀和
	//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	//gluBuild2DMipmapLevels();
	//gluBuild3DMipmaps();
}
 
void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glBegin(GL_QUADS);
	GLfloat endCoordValue = 12.0f;
//http://my.oschina.net/sweetdark/blog/177812
    glTexCoord2f(0.0, 0.0); 
	glVertex3f(-2.0, -1.0, 0.0);
 
	glTexCoord2f(0.0, endCoordValue); //8.0
	glVertex3f(-2.0, 1.0, 0.0);
 
	glTexCoord2f(endCoordValue, endCoordValue);
	glVertex3f(2000.0, 1.0, -6000.0);
 
	glTexCoord2f(endCoordValue, 0.0);
	glVertex3f(2000.0, -1.0, -6000.0);
    glEnd();
    glFlush();
}
 
void myReshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60.0, 1.0*(GLfloat)w/(GLfloat)h, 1.0, 30000.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}
 
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize (500, 500);
    glutCreateWindow (argv[0]);
    myinit();
    glutReshapeFunc (myReshape);
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;             /* ANSI C requires main to return int. */
}