Re: [Mesa3d-users] GL_POINT_DISTANCE_ATTENUATION

[Owen K. <Owe...@sc...>]

Hi Brian,

Sure, here is the best illustration of the issue I could produce: 1000 
points, aligned as you suggested.
If I bring the point size up from 1.0 the issue isn't as obvious 
although still noticeable.
The attenuation seems to drop the point size then gradually increase, 
you can see the points towards the back disappear then reappear.
Attached modified program and two screen shots, one using osmesa and the 
other with glut+video card gl drivers.

Thanks,
Owen.

Brian Paul wrote:
> Owen Kaluza wrote:
>> Hello,
>> I'm having trouble with point distance attenuation using OSMesa.
>> I'm rendering a lot of depth sorted, alpha blended, textured points and
>> dark bands are appearing that are not there when I render with the
>> system GL.
>>
>> I found the problem only occurs with point distance attenuation 
>> turned on.
>> If you look at the attached image you can see there are clearly defined
>> bands, possibly the point size calculation is incorrect at certain
>> distances resulting in size jumps.
>>
>> I've attached a sample program that reproduces the problem. Also tried
>> the latest Mesalib code (Mesa-7.7-devel-20091105) and is still 
>> occurring.
>
> Could you prune down your test program a bit?  Perhaps you could draw 
> a series of points between the min/max Z positions and see how they look.
>
> -Brian
>