Re: [Mesa3d-users] GL_POINT_DISTANCE_ATTENUATION

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

Ah no worries, thanks for checking it out. Not a priority, mainly just 
reporting as a bug or in case it was a very easy fix.
Owen.

Brian Paul wrote:
> OK, the problem is we're not doing sub-pixel adjustment of texcoords 
> in the sprite rasterization code.  Look in sprite_point() in 
> s_points.c if interested.  This can be fixed but it will take some 
> work.  I'll see if I can fix it when I get some spare time.
>
> -Brian
>
>
> Owen Kaluza wrote:
>   
>> 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
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
>>>       
>
>
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