混合问题从OpenGLES 1.0移植到2.0（iOS）(Blending issue porting from OpenGLES 1.0 to 2.0 (iOS))

 我正在将一个非常简单的代码从OpenGLES 1.0移植到OpenGLES 2.0。 
 
 在原始版本中，我启用了混合功能 
 
glEnable(GL_BLEND);
glBlendEquation(GL_FUNC_ADD);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
 
 我在ES 2.0实现中使用相同的代码，因为我需要将新渲染的四边形与渲染缓冲区中的内容混合（我保留渲染缓冲区，我无法重新渲染场景）。 
 
 我正在使用纹理（显示从中心到外部的径向渐变的alpha值，alpha从1变为0）作为alpha蒙版，仅包含具有不同alpha值的白色像素。 我给我的顶点相同的颜色说红色，alpha为100/255。 我的背景是透明的黑色。 在那之下，我有一个纯白色的表面（UIView）。 我渲染4个四边形。 
 
 OpenGLES 1.0的结果（期望的结果） 
 
 我的观察告诉我片段着色器应该只是： 
 
gl_FragColor = DestinationColor * texture2D(Texture, TexCoordOut);
 
 （我通过尝试不同的顶点和纹理值来得出这个结论。这也是我在一些教程中读到的。） 
 
 我正在尝试编写一些OpenGL 2.0代码（包括顶点+片段着色器），它会给我与OpenGLES 1.0完全相同的结果，仅此而已。 除了在纹理上应用顶点颜色之外，我不需要/想要在片段着色器中进行任何类型的混合。 使用简单着色器，这是我得到的结果： 
 
 我几乎尝试了*，+，mix的每一个组合，但我无法重现相同的结果。 这是我到目前为止最接近的，但这绝对不是正确的（这也没有任何意义） 
 
varying lowp vec4 DestinationColor;
varying lowp vec2 TexCoordOut;
uniform sampler2D Texture;

void main(void) {
    lowp vec4 texture0Color = texture2D(Texture, TexCoordOut);
    gl_FragColor.rgb = mix(texture0Color.rgb, DestinationColor.rgb, texture0Color.a);
    gl_FragColor.a = texture0Color.a * DestinationColor.a;
}
 
 这个着色器给了我以下内容： 

I'm porting a very simple piece of code from OpenGLES 1.0 to OpenGLES 2.0.
 
In the original version, I have blending enabled with
 
glEnable(GL_BLEND);
glBlendEquation(GL_FUNC_ADD);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
 
I'm using the same code in my ES 2.0 implementation as I need to blend the newly rendered quads with what was in the render buffer (I'm retaining the render buffer, I can't re-render the scene).
 
I'm using a texture (alpha values displaying a radial gradient from center to the outside, alpha goes from 1 to 0) that serves as an alpha mask, containing only white pixels with different alpha values. I give my vertices the same color say red with alpha of 100/255. My background is transparent black. Below that, I have a plain white surface (UIView). I render 4 quads.
 
Result with OpenGLES 1.0 (desired result) 
 
My observations tells me that the fragment shader should simply be:
 
gl_FragColor = DestinationColor * texture2D(Texture, TexCoordOut);
 
(I got to that conclusion by trying different values for my vertices and the texture. That's also what I've read on some tutorials.)
 
I'm trying to write some OpenGL 2.0 code (including vertex + fragment shaders) that would give me the exact same result as in OpenGLES 1.0, nothing more, nothing less. I don't need/want to do any kind of blending in the fragment shader except applying the vertex color on the texture. Using the simple shader, here's the result I got: 
 
I tried pretty much every combination of *, +, mix I could think of but I couldn't reproduce the same result. This is the closest I got so far, but that's definitely not the right one (and that doesn't make any sense either)
 
varying lowp vec4 DestinationColor;
varying lowp vec2 TexCoordOut;
uniform sampler2D Texture;

void main(void) {
    lowp vec4 texture0Color = texture2D(Texture, TexCoordOut);
    gl_FragColor.rgb = mix(texture0Color.rgb, DestinationColor.rgb, texture0Color.a);
    gl_FragColor.a = texture0Color.a * DestinationColor.a;
}
 
This shader gives me the following: 

原文：https://stackoverflow.com/questions/17457327