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android/opengles alpha textures not semitransparent but binary transparent

Started by ehmdjii Sep 6, 2010 at 5:34 AM 3 replies 1.6k views

Original Post

Sep 6, 2010 at 5:34 AM

hello, i am drawing some textures with alpha channel, but when they are displayed it looks like the alpha channel is only binary. so a pixel is either transparent or opaque, although in the texture file itself the pixel is half-transparent.

is there a workaround for this problem?

the above shows how it should be like, and the below shows how it is:

Hodgman

Sep 6, 2010 at 6:17 AM

You should show the code for how you're enabling transparency. It sounds like you're enabling alpha testing instead of alpha blending.

ehmdjii

Sep 6, 2010 at 6:20 AM

ok, this is how the blending is set up:

gl.glEnable(GL10.GL_BLEND);
gl.glBlendFunc(GL10.GL_ONE, GL10.GL_ONE_MINUS_SRC_ALPHA);

relsoft

Sep 6, 2010 at 6:56 AM

Did you try:

glBlendFunc(GL_SRC_ALPHA, GL_ONE)

ehmdjii

Sep 6, 2010 at 7:48 AM

thanks for the hint. actually
gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);

did the trick.

however i am not sure if i want to use that. since on all my desktop opengl apps i use

gl.glBlendFunc(GL10.GL_ONE, GL10.GL_ONE_MINUS_SRC_ALPHA);
in conjunction with premultiplied alpha and it works fine!

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