Poor graphics / Banding issues

[Francky033]

When I'm running my program, I get an image that seems to have severe banding issues. That is, the transition between colors isn't smooth, but rather there appear to be bands. I suppose my problem is coming from a bit-depth configuration too low (8 bits).
How to configure with QT and OpenGl better floating-point textures and get a better rendering? ?

Thanks !

[raven-worx]

@Francky033 said in Poor graphics / Banding issues:

When I'm running my program

you should be more specific what your application consists of.
What are you displaying and how specifically.

[Francky033]

Yes... I'm sorry...
It's a planetarium and I'm trying to get a good quality sky gradient on the horizon. I use Qt 5.10 and opengl 3.0.
I created a vertical tube that has a transparency of 0.0 at its top and 1.0 at its base that allows to get this gradient. But the result is mediocre, with irregularities appearing in the colors...
I suppose that an 8-bit buffer of each color doesn't allow good quality gradients...
I tried to increase the size of the buffers of each color.

from that
format. setBlueBufferSize (8);
format. setRedBufferSize (8);
format. setGreenBufferSize (8);
to :
format. setBlueBufferSize (16);
format. setRedBufferSize (16);
format. setGreenBufferSize (16);

but without success..

How can we improve things?

[raven-worx]

@Francky033
so that means you are using QGLWidget or QML?

[Francky033]

I'm using a QOpenGLWidget...

[mrjj]

Hi
Not into openGl so much but i wondering if
8bit openGl means palette based ?
(256 colors available)
In that case gradients will look awful. :)

what are you using 8bit ?
(for retro look games, normally you would alter the assets to
use a common 256 color palette and then just render that)

[Francky033]

No, I'm talking about 8 bits for each color channel i. e. for each pixel channel r, g, b, a (8x4 = 32 bits)
Use Bayer's matrix maybe?
http://www.anisopteragames.com/how-to-fix-color-banding-with-dithering/

[mrjj]

@Francky033
Ah, that way. The BM methods sounds worth trying at least to see how
big effect it will have.