OpenGL笔记：纹理的初次使用

说明

纹理的代码写完后，一直出不来结果，原因是没有设置GL_TEXTURE_MIN_FILTER，它的默认值为GL_NEAREST_MIPMAP_LINEAR，因为这里我还没用到Mipmap，所以使用这个默认值，结果是错误的，关于mipmap后面再学习。

代码

#define FREEGLUT_STATIC
#include "gl/freeglut.h"
#include <vector>#include <iostream>
#include <vector>#define MY_PI_VALUE (3.141592653)GLfloat fAngleBaseOnXAxis = 0.0; //角度
GLfloat fAngleBaseOnYAxis = 0.0; //角度
GLfloat fAngleStep = 5.0; //角度增加值
const float g_fAxisRange = 1000.0f;void DrawBox()
{glEnable(GL_TEXTURE_2D);GLubyte myTexImg[4][4][3] = {{ { 0x00, 0x00, 0xff }, { 0xff, 0x00, 0x00 }, { 0x00, 0x00, 0xff }, { 0xff, 0x00, 0x00 } },{ { 0xff, 0x00, 0x00 }, { 0x00, 0x00, 0xff }, { 0xff, 0x00, 0x00 }, { 0x00, 0x00, 0xff } },{ { 0x00, 0x00, 0xff }, { 0xff, 0x00, 0x00 }, { 0x00, 0x00, 0xff }, { 0xff, 0x00, 0x00 } },{ { 0xff, 0x00, 0x00 }, { 0x00, 0x00, 0xff }, { 0xff, 0x00, 0x00 }, { 0x00, 0x00, 0xff } }};//GL_TEXTURE_MIN_FILTER的设置很重要，否则纹理出不来//The initial value of GL_TEXTURE_MIN_FILTER is GL_NEAREST_MIPMAP_LINEAR.//The initial value of GL_TEXTURE_MAG_FILTER is GL_LINEAR.glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 4, 4, 0, GL_RGB, GL_UNSIGNED_BYTE, myTexImg);glBegin(GL_QUADS);double dSize = 500.0;//上glNormal3d(0, 0, 1.0);glTexCoord2d(0.0, 0.0);glVertex3d(0.0, 0.0, 0.0);glTexCoord2d(1.0, 0.0);glVertex3d(dSize, 0.0, 0.0);glTexCoord2d(1.0, 1.0);glVertex3d(dSize, dSize, 0.0);glTexCoord2d(0.0, 1.0);glVertex3d(0.0, dSize, 0.0);//下glNormal3d(0, 0, -1.0);glVertex3d(0.0, 0.0, -dSize);glVertex3d(0.0, dSize, -dSize);glVertex3d(dSize, dSize, -dSize);glVertex3d(dSize, 0.0, -dSize);//左glNormal3d(-1.0, 0.0, 0.0);glTexCoord2d(0.0, 0.0);glVertex3d(0.0, 0.0, 0.0);glTexCoord2d(1.0, 0.0);glVertex3d(0.0, dSize, 0.0);glTexCoord2d(1.0, 1.0);glVertex3d(0.0, dSize, -dSize);glTexCoord2d(0.0, 1.0);glVertex3d(0.0, 0.0, -dSize);//右glNormal3d(1.0, 0.0, 0.0);glVertex3d(dSize, 0.0, 0.0);glVertex3d(dSize, 0.0, -dSize);glVertex3d(dSize, dSize, -dSize);glVertex3d(dSize, dSize, 0.0);//前glNormal3d(0.0, -1.0, 0.0);glVertex3d(0.0, 0.0, 0.0);glVertex3d(0.0, 0.0, -dSize);glVertex3d(dSize, 0.0, -dSize);glVertex3d(dSize, 0.0, 0.0);//后glNormal3d(0.0, 1.0, 0.0);glVertex3d(0.0, dSize, 0.0);glVertex3d(dSize, dSize, 0.0);glVertex3d(dSize, dSize, -dSize);glVertex3d(0.0, dSize, -dSize);glEnd();
}void OnDisplay()
{glEnable(GL_LIGHTING);glEnable(GL_DEPTH_TEST);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);//光照glEnable(GL_LIGHT0);GLfloat fAmbients[] = { 0.1, 0.1, 0.1, 1.0 };GLfloat fDiffuse[] = { 0.9, 0.9, 0.9, 1.0 };GLfloat fSpecular[] = { 1.0, 1.0, 1.0, 1.0 };GLfloat fLightPos[] = { 0.0, 0.0, 1.0, 0.0 };glLightfv(GL_LIGHT0, GL_AMBIENT, fAmbients);glLightfv(GL_LIGHT0, GL_DIFFUSE, fDiffuse);glLightfv(GL_LIGHT0, GL_SPECULAR, fSpecular);glLightfv(GL_LIGHT0, GL_POSITION, fLightPos);glPushMatrix();//glTranslatef(100, 100, 0);glRotatef(fAngleBaseOnXAxis, 1.0, 0.0, 0.0);glRotatef(fAngleBaseOnYAxis, 0.0, 1.0, 0.0);glEnable(GL_COLOR_MATERIAL);glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);DrawBox();glPopMatrix();glFlush();
}void OnEventSpecialKey(int key, int x, int y)
{if (key == GLUT_KEY_LEFT){//绕y轴顺时针fAngleBaseOnYAxis -= fAngleStep;}else if (key == GLUT_KEY_RIGHT){//绕y轴逆时针fAngleBaseOnYAxis += fAngleStep;}else if (key == GLUT_KEY_UP){//绕x轴顺时针fAngleBaseOnXAxis -= fAngleStep;}else if (key == GLUT_KEY_DOWN){//绕x轴逆时针fAngleBaseOnXAxis += fAngleStep;}//XXX：此处是不是这样调用呢？//OnDisplay();glutPostRedisplay();
}void OnReshape(int nWidth, int nHeight)
{if (nWidth == 0) nWidth = 1;if (nHeight == 0) nHeight = 1;glViewport(0, 0, nWidth, nHeight);glMatrixMode(GL_PROJECTION);glLoadIdentity();if (nWidth > nHeight){glOrtho(-g_fAxisRange * nWidth / nHeight, g_fAxisRange * nWidth / nHeight,-g_fAxisRange, g_fAxisRange, -g_fAxisRange, g_fAxisRange);}else{glOrtho(-g_fAxisRange, g_fAxisRange, -g_fAxisRange * nHeight / nWidth,g_fAxisRange * nHeight / nWidth, -g_fAxisRange, g_fAxisRange);}glMatrixMode(GL_MODELVIEW);
}int main(int argc, char** argv)
{glutInit(&argc, argv);glutInitWindowSize(400, 400);glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);glutCreateWindow("Texture");glutDisplayFunc(OnDisplay); //必须在glutCreateWindow之后，否则设置会失败glutReshapeFunc(OnReshape);glutSpecialFunc(OnEventSpecialKey);glMatrixMode(GL_PROJECTION);glLoadIdentity();glOrtho(-g_fAxisRange, g_fAxisRange, -g_fAxisRange, g_fAxisRange, -g_fAxisRange, g_fAxisRange);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt(0, 0, 0, 0, 0, -1, 0, 1, 0); //俯视图//gluLookAt(0, 0, 0, 0, 1, 0, 0, 0, 1); //主视图//gluLookAt(0, 0, 0, 0, -1, 0, 0, 0, -1);//gluLookAt(0, 0, 0, 1, -1, -1, 0, 1, 0);glClearColor(0.0f, 0.0f, 0.0f, 1.0f);glutMainLoop();return 0;
}