OpenGLES + Framebuffer artifacts

Question

Using OpenGLES 1.1 (don't have a choice at this time). Target OS is Android.

I'm having some inconsistency when rendering to the main framebuffer, and when rendering to a texture.

When I render to the normal screen, everything is fine. When I render to a texture, I get a dark rim around my graphics wherever alpha is translucent.

Here's my helper functions:

void RenderNormal()
{
    if (!gIsRenderToTexture)
    {
        glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
        glBlendEquationOES(GL_FUNC_ADD_OES);
    }
    else
    {
        glBlendFuncSeparateOES(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA,GL_ONE,GL_ONE_MINUS_SRC_ALPHA);
        glBlendEquationSeparateOES(GL_FUNC_ADD_OES,GL_FUNC_ADD_OES);
    }
}

void RenderAdditive()
{
    glBlendFunc(GL_SRC_ALPHA, GL_ONE);
}

void RenderMultiply()
{
    glBlendFunc(GL_ZERO, GL_SRC_COLOR);
}

So, some data:

On newer systems, this works just fine (also on iOS, OSX, and Linux)
On Kindle Fire, I still get the dark rims.
On an older Android device running KitKat, my additive/multiply functions don't turn off (I assume because of juggling between glBlendFunc and glBlendFuncSeparate... I'm not turning something off, but whatever I try to do to fix it makes it worse)

I'm looking for a way to square these three functions so that they can operate both with render to texture, and with rendering to the normal ol' screen. Can you assist?

Yep... the issue appears to be with drawing on zero alpha (as opposed to 1 alpha of the normal framebuffer). I am using render targets as "layers" in the game I'm working on. Also, note that on newer devices, it works... so I suspect there is some housekeeping that is not needed on newer devices that needs doing on older ones. — Raptisoft, Jul 12 '17 at 19:16
Because I'm using it as a transparent layer... wherever I don't draw, I want transparent. — Raptisoft, Jul 13 '17 at 15:32

score 0 · Answer 1 · answered Jul 13 '17 at 17:58

Okay, a day of working and research and I finally figure out that on the target device, the OES are not supported. So that said, anyone having this problem... the Kindle Fire and a lot of older tablets just outright don't support glBlendFuncSeparateOES or glBlendEquationOES and they will fail SILENTLY.

OpenGLES + Framebuffer artifacts

1 Answers1