OpenGL学习三十九：飘动的旗帜

(此节内容对应NEHE教程第11课)

 

目前为止我们做的例子都是平面的，这个例子是带有波动效果的，

2维图形包括X，Y两个坐标系。因此看到的是平面的。
3维图形由X,Y,Z三个坐标系构成，当Z坐标不为0时，可以产生3维的效果。一个图片或图形由许多个3维图形构成是，并且Z是变化的 就会产生波动的效果

for(int x=0; x<45; x++)
 {
  // 沿Y平面循环
  for(int y=0; y<45; y++)
  {
   // 向表面添加波浪效果
   points[x][y][0]=float((x/5.0f)-4.5f);
   points[x][y][1]=float((y/5.0f)-4.5f);
   points[x][y][2]=float(sin((((x/5.0f)*40.0f)/360.0f)*3.141592654*2.0f));
  }
 }

多边形填充方式，glPolygonMode()

glPolygonMode( GL_BACK, GL_FILL );   // 后表面完全填充
glPolygonMode( GL_FRONT, GL_LINE );   // 前表面使用线条绘制

#include "header.h"

float points[45][45][3];   
int wiggle_count = 0;		

GLfloat	xrot;	
GLfloat	yrot;				
GLfloat	zrot;			
GLfloat hold;		

GLuint	texture[1];		

AUX_RGBImageRec *LoadBMP(char *Filename)			
{
	FILE *File=NULL;								

	if (!Filename)									
	{
		return NULL;								
	}

	File=fopen(Filename,"r");						

	if (File)											
	{
		fclose(File);									
		return auxDIBImageLoad(Filename);				
	}

	return NULL;										
}

int LoadGLTextures()								
{
	int Status=FALSE;									

	AUX_RGBImageRec *TextureImage[1];					

	memset(TextureImage,0,sizeof(void *)*1);           

	// Load The Bitmap, Check For Errors, If Bitmap's Not Found Quit
	if (TextureImage[0]=LoadBMP("Data/Tim.bmp"))
	{
		Status=TRUE;									

		glGenTextures(1, &texture[0]);					

		// Typical Texture Generation Using Data From The Bitmap
		glBindTexture(GL_TEXTURE_2D, texture[0]);
		glTexImage2D(GL_TEXTURE_2D, 0, 3, TextureImage[0]->sizeX, TextureImage[0]->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->data);
		glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
		glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
	}

	if (TextureImage[0])									
	{
		if (TextureImage[0]->data)							
		{
			free(TextureImage[0]->data);				
		}

		free(TextureImage[0]);								
	}

	return Status;										
}

void ReSizeGLScene(GLsizei width, GLsizei height)		
{
	if (height==0)										
	{
		height=1;										
	}

	glViewport(0,0,width,height);						

	glMatrixMode(GL_PROJECTION);						
	glLoadIdentity();								

	// Calculate The Aspect Ratio Of The Window
	gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

	glMatrixMode(GL_MODELVIEW);							
	glLoadIdentity();								
}

int InitGL(void)										
{
	if (!LoadGLTextures())								
	{
		return FALSE;								
	}

	glEnable(GL_TEXTURE_2D);							
	glShadeModel(GL_SMOOTH);							
	glClearColor(0.0f, 0.0f, 0.0f, 0.5f);				
	glClearDepth(1.0f);									
	glEnable(GL_DEPTH_TEST);							
	glDepthFunc(GL_LEQUAL);								
	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
	glPolygonMode( GL_BACK, GL_FILL );					
	glPolygonMode( GL_FRONT, GL_LINE );					

	for(int x=0; x<45; x++)
	{
		for(int y=0; y<45; y++)
		{
			points[x][y][0]=float((x/5.0f)-4.5f);
			points[x][y][1]=float((y/5.0f)-4.5f);
			points[x][y][2]=float(sin((((x/5.0f)*40.0f)/360.0f)*3.141592654*2.0f));
		}
	}

	return TRUE;									
}

void DrawGLScene(void)							
{
	int x, y;
	float float_x, float_y, float_xb, float_yb;

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	
	glLoadIdentity();									

	glTranslatef(0.0f,0.0f,-12.0f);

	glRotatef(xrot,1.0f,0.0f,0.0f);
	glRotatef(yrot,0.0f,1.0f,0.0f);  
	glRotatef(zrot,0.0f,0.0f,1.0f);

	glBindTexture(GL_TEXTURE_2D, texture[0]);

	glBegin(GL_QUADS);
	for( x = 0; x < 44; x++ )
	{
		for( y = 0; y < 44; y++ )
		{
			float_x = float(x)/44.0f;
			float_y = float(y)/44.0f;
			float_xb = float(x+1)/44.0f;
			float_yb = float(y+1)/44.0f;

			glTexCoord2f( float_x, float_y);
			glVertex3f( points[x][y][0], points[x][y][1], points[x][y][2] );

			glTexCoord2f( float_x, float_yb );
			glVertex3f( points[x][y+1][0], points[x][y+1][1], points[x][y+1][2] );

			glTexCoord2f( float_xb, float_yb );
			glVertex3f( points[x+1][y+1][0], points[x+1][y+1][1], points[x+1][y+1][2] );

			glTexCoord2f( float_xb, float_y );
			glVertex3f( points[x+1][y][0], points[x+1][y][1], points[x+1][y][2] );
		}
	}
	glEnd();

	if( wiggle_count == 2 )
	{
		for( y = 0; y < 45; y++ )
		{
			hold=points[0][y][2];
			for( x = 0; x < 44; x++)
			{
				points[x][y][2] = points[x+1][y][2];
			}
			points[44][y][2]=hold;
		}
		wiggle_count = 0;
	}

	wiggle_count++;

	glFlush();							
}


void rotate()
{
	xrot+=0.3f;
	yrot+=0.2f;
	zrot+=0.4f;

	glutPostRedisplay();
}
void keyboard(unsigned char key,int x,int y)
{
	switch (key)
	{

	case 'S':
		glutIdleFunc(rotate);
		break;
	case 'R':
		glutIdleFunc(NULL);
		break;
	}

}


int main(int argc,char **argv)
{
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB|GLUT_DEPTH);
	glutInitWindowSize(800,600);
	glutInitWindowPosition(100,100);
	glutCreateWindow("飘动的旗帜");
	InitGL();
	glutDisplayFunc(DrawGLScene);
	glutKeyboardFunc(keyboard);
	glutReshapeFunc(ReSizeGLScene);
	glutMainLoop();
}