如何在OpenGl实现透明纹理贴图？

Question

先要将图的alpha值设置一下，即将透明的地方先用但一色表示，然后遇到该颜色
则将其alpha值设为1，其他可以保持不变
这样就可以在opengl夏读入了,注意激活融合

Answer 1

上清华bbs的虚拟现实技术版看看
有一段代码
我写的，关于画树

Answer 2

ruixp:
   能不能给我发一个，[email protected]
                               谢谢

Answer 3

ruixp:
  能不能给我发一个，[email protected]
                              谢谢

Answer 4

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);
}