ccDrawLine不透明度？ [英] ccDrawLine opacity?

问题描述

我对所有OpenGL调用都很新，但是幸运的是cocos2d很容易让我在屏幕上画线，如下：

   - （void）draw {
 glColor4f（255，255，255,255）; 
 ccDrawLine（ccp（150,110），ccp（280,230））; 
} 
  

我得到一个白线。

但现在，我想让它有点透明，所以我把alpha值改为100.但是，线仍然明亮和白色。然后我假设值实际上可以从0.0到1.0。

解决方案

您肯定需要先启用混合：

  glEnable（GL_BLEND）; 
 glBlendFunc（GL_SRC_ALPHA，GL_ONE_MINUS_SRC_ALPHA）; 
 glColor4ub（255，255，255,100）; 
 ccDrawLine（ccp（0,110），ccp（280,230））;另外请注意，glColor4ub接受无符号字节（每个参数为0-255），而
 
 
 
 
祝你好运！
 
I am very new to all those OpenGL calls, but fortunately cocos2d will easily let me draw lines on the screen, like this:
-(void)draw {
    glColor4f(255, 255, 255,255);
    ccDrawLine(ccp(150,110), ccp(280,230));
}
And I get a white line.

But now, I want to make it a bit transparent, so I change the alpha value to 100. However, the line is still bright and white. Then I assumed that the values could actually range from 0.0 to 1.0. I set it to 0.2 but still no change.

Why is that?
解决方案
You definitely need to enable blending first:
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glColor4ub(255, 255, 255,100);
ccDrawLine(ccp(0,110), ccp(280,230));
Also note that "glColor4ub" takes in unsigned bytes (0-255 for each parameter) while
"glColor4f" takes in 4 floats (0-1.0 for each parameter). Use whichever you are comfortable with. 

Good luck!

                        
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