如何在OpenGl实现透明纹理贴图？(转)

如何在OpenGl实现透明纹理贴图？(转)

2008-11-05 13:40

void CVCITYView::DrawTree()//绘制树 
{ 
///////////////////////////// 
/////////画树程序//////////// 
///////////////////////////// 
CTree tree; 
tree.getTree(tree); 

AUX_RGBImageRec* myimage; 
unsigned char *image; 
myimage=auxDIBImageLoad("tree1.bmp"); 
//makeTexture(myimage); 
int width,height; 
width=myimage->sizeX; 
height=myimage->sizeY; 
FILE *fp; 
fp=fopen("tree1.bmp","rb"); 
if(!fp) return; 
fseek(fp,54,SEEK_SET);////读取24位真彩色位图 
image=(unsigned char *)malloc(width*height*3); 
int rc; 
rc=fread(image,sizeof(unsigned char),width*height*3,fp); 
fclose(fp); 
BYTE texture[256][256][4];//注意：每个像素占用4个字节，不是原来的3个。 
for(int i=0;i<width;i++) 
{ 
for(int j=0;j<height;j++) 
{ 
//把颜色值写入 
texture[i][j][0] = (GLubyte)*(image+i*width*3+j*3); 
texture[i][j][1] = (GLubyte)*(image+i*width*3+j*3+1); 
texture[i][j][2] = (GLubyte)*(image+i*width*3+j*3+2); 
//设置alpha值,假设白色为透明色 
if(texture[i][j][0]==255 && texture[i][j][1]==255 && texture[i][j][2]==255) 
texture[i][j][3] = 0;//透明，设为 0 
else 
texture[i][j][3] = 255;//不透明，设为 255, 也就是以后用的1.0 
} 
} 

//映射纹理 
glPixelStorei(GL_UNPACK_ALIGNMENT,1); 
glTexImage2D(GL_TEXTURE_2D,0,4,width,height,0, GL_RGBA, GL_UNSIGNED_BYTE,texture); 
gluBuild2DMipmaps(GL_TEXTURE_2D,4,width,height,GL_RGBA,GL_UNSIGNED_BYTE,texture); 
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP); 
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP); 
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST); 
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST); 
glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_MODULATE); 
glEnable(GL_TEXTURE_2D); 
glEnable(GL_BLEND); 
glEnable(GL_ALPHA_TEST); 
glAlphaFunc(GL_GREATER ,0.9);//0.5可以换成任何在0~1之间的数 
for(i=1;i<198;i++) 
{ 
glBegin(GL_QUADS); 
glTexCoord2d(0,0); 
glVertex3d(tree.TreePoint[i].x-0.5,tree.TreePoint[i].y,0.0); 
glTexCoord2d(1,0); 
glVertex3d(tree.TreePoint[i].x+0.5,tree.TreePoint[i].y,0.0); 
glTexCoord2d(1,1); 
glVertex3d(tree.TreePoint[i].x+0.5,tree.TreePoint[i].y,3); 
glTexCoord2d(0,1); 
glVertex3d(tree.TreePoint[i].x-0.5,tree.TreePoint[i].y,3); 
glEnd(); 
} 
glDisable(GL_TEXTURE_2D); 
glDisable(GL_ALPHA_TEST); 
glDisable(GL_BLEND); 
}