[Bf-committers] Back Buffer Issues

[Ton Roosendaal]

Hi,

Blender likes the SwapCopy a lot. :)
This is becoming a standard in many (PC) cards now, and for some  
systems you cannot even tweak it... for example Macs only support this  
method.

The Swap-Exchange could work too, it is the old Blender default from  
the SGI period, but for it to work 100% I need someone with such a  
graphics card system who's devoted to get it to work. Not difficult  
coding, just tracking all little things in the code to keep it  
swap-exchange compatible.

A year ago we discussed this here too, with Daniel Dunbar, going over  
the best buffer strategy with Blender. The conclusion back then was to  
go for 100% swap-copy, and code exceptions for the (older) systems that  
don't support this.

Now, what's there to fix?

-Ton-



On 2 Dec, 2004, at 19:25, Matthew H. Plough wrote:

> Hi all!!
>
> I was playing around with my video card's OpenGL settings this  
> morning, and found an interesting clue on what's causing the odd  
> corruption shown in  
> http://www.princeton.edu/~mplough/tmp/buttons_error.png .
> First things first: I have a 3Dlabs Wildcat Realizm 200.
>
> Second things second ;) : Like most cards, my card has two options for  
> dealing with double buffering -- page flipping (which only exchanges  
> the front and back buffer pointers) and Force Swap Copy (which  
> maintains a dedicated back buffer and a dedicated display buffer).   
> When a buffer swap happens in forced mode, data from the back buffer  
> is *copied* into the display buffer, but is not cleared.  My best  
> interpretation of Blender's code leads me to believe that it depends  
> on this preservation of back buffer data.
> Is this in fact the case?  If so, how can we fix this?
>
> Matt
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>
------------------------------------------------------------------------ 
--
Ton Roosendaal  Blender Foundation ton at blender.org  
http://www.blender.org