glBlendFuncSeparate in RenderTexture

cocos2d-x C++
#1

Found out that in cocos2d-x 3 RenderTexture has premultiplied alpha, so I need to use the following code for my RenderTexture to look the same as with cocos2d-x 2.
glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

Everything works OK if I call the function in draw(Renderer *renderer, const kmMat4 &transform, bool transformUpdated). But I guess I have to call GL::blendResetToCache after it. If I do, the blend func gets reset and everything is wrong again (because actual draw is done in a separate function). The question is where should I call the glBlendFuncSeparate, shouldn’t it be added to Node just as setBlendFunc, so that it is set right before actual rendering?

#2

Hi Elvman,
Did you find the answer for your question. I also want RenderTexture to behave just the way it used to in v2.x.

#3

No, I haven’t found the answer. I can’t find a way to change blending options just before the sprite is rendered.

#4

Hey guys, I too need glBlendFuncSeparate support for the RenderTexture sprite. (I’m testing on WP8)
At least I think so… I’m drawing sprites onto a Node then drawing that Node onto a RenderTexture.
Cocos is then drawing the RenderTexture, but with the alpha premultiplied on the sprites.
I’ve had a similar issue on iOS with my own engine, I solved it with
glBlendFuncSeparateOES(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

You guys had any luck in solving this?
(first post)

#5

Quick update, OK found a kind of solution…
was doing some digging and in “cocos2d-x\cocos\2d\ccGLStateCache.cpp” and inside SetBlending(GLenum sfactor, GLenum dfactor) on line 114, I replaced:
glBlendFunc(sfactor, dfactor);
with
glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
This gave me the result I was looking for, I know its not the correct way to fix it but thought it was a useful enough solution for you guys right now.
:slight_smile: