Re: Caching with custom elements

[Roger H. <rog...@mi...>]

On 13 Feb, 2007, at 23:49, James Walker wrote:

> In the renderers, I'm using a custom element to cache an optimized
> version of a TriMesh.  The element contains an edit index along  
> with the
> TriMesh reference, so that a stale cache can be detected.  That works
> fine in principle, though there's a bug at the moment.
>
> But now suppose I have another similar custom element, say to cache a
> triangle strip.  When I update the triangle strip, it bumps the edit
> index, so the other cache becomes stale.  Which causes the other cache
> to get updated, bumping the edit index, which makes the triangle cache
> stale...
>
> How can I get out of this infinite loop?  The simplest way, I suppose,
> would be to add a Q3Shared_SetEditIndex function, and use it when
> setting these cache elements. Is there a more elegant way I haven't
> thought of?
> -- 


I don't exactly understand what you are trying to do. You have an  
object A
which has two caches B and C, both of which hold the edit index of A.
Why would updating B or C update the edit index of A?

Or is C a cache of B? If so, C holds the edit indexes of A and B. If  
A gets changed,
its edit index gets modified. When you need C it checks both edit  
indexes,
if A's has changed it forces B to recache then recaches itself. If  
you need B
first then it recaches itself and when you need C it finds both  
indexes are stale,
so gives B a chance to recache (which it decided not to do as its  
edit index
for A is still fresh), and then C recaches itself.

Roger.