iPhone opengl es alpha-blending。边缘有黑色 [英] iPhone opengl es alpha-blending. I have black color in edge

问题描述

我正在开发iPhone游戏。我有下面的源图像将其绘制到背景。源图像具有alpha 0x00和边缘周围的渐变，背景的alpha为0xff。当我将源图像绘制到背景时，我会看到黑色，就像您可以看到结果图像一样。我正在使用OpenGL ES glBlendFunc（GL_SRC_ALPHA，GL_ONE_MINUS_SRC_ALPHA）方法。我已经改变了所有可能的论点，但每次都没有被移动。

I am developing iPhone game. I have the below Source image to draw it to the background. The Source image has alpha 0x00 and gradation around edge and the background's alpha is 0xff. When I draw the source image to the background, I have black color like you could see the Result image. I am using OpenGL ES glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) method. I have changed every possible arguments, but every time it is not moved.

为什么我在源图像的边缘有黑色？问题是什么？ iPhone中的每个游戏都不会使用渐变吗？

Why do I have the black color in the edge of the source image? What is the problem? Does not every games in iphone use gradation?

我是否需要制作渐变的源图像？

Do I need to make the source image with out gradation?

有没有人知道解决方案？

Does anyone know the solution?

源图片：

结果图片：

推荐答案

你的图像是否预先乘以alpha？然后你应该使用

Does your image have pre-multiplied alpha? Then you should be using

glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

这里是对它的解释。

注意：我做了一些研究后重写了答案。提到的文章 rotoglup 对正在发生的事情有一些了解，它比我原来的公式更有意义。我还试着看看其他人在他们的代码中使用了什么，看起来这个公式是最常用的。令人惊讶的是，3D图形中像阿尔法混合这样的基本内容如此具有争议性，每个人似乎都在重新发明轮子并提出自己的解决方案。

Note: I rewrote the answer after doing some research. The article rotoglup mentioned has some insight on what's going on and it makes more sense then my original formula. I also tried to see what other people are using in their code and it looks like this formula is the most used one. It's amazing how such a basic thing in 3D graphics as alpha blending can be so controversial and everyone seems to reinvent the wheel and come up with their own solutions.

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