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;
}