[Bf-committers] point cache

bjornmose at gmx.net bjornmose at gmx.net
Fri Feb 29 13:39:48 CET 2008

Ah, i see
that is not only a logical issue  but raises some physical problems too:
For example, if you increase the number of vertexes you would increase the mass of the system, since the mass parameter at least with soft bodies is the per vertex mass. I think as soon as the "particles" start interacting they definitely will change their behavior on resolution changes. 

So what ever you have in the cache if you have anything at low resolution might be but is not guaranteed to be close to the higher resolution system.
Looking at i that way it should be clear, that in some situations recalculating at render time might yield unexpected / unwanted / never seen before results.
I don't even think there is a general "right" way to spread the needed information to the higher resolution object. Think of goal painting to pin the corners of a sheet, should the subsurfed vertexes be "half" pinned?
I don't know how much the particle system is stuck by that.

Well at least i think if we have a different number of vertexes at render time things have to be recalculated. And i don't think it violates the definition of cache " if we have something already hand it back "  we simply don't have the thing we are asked for. Still there is the risk rendering a physical system you have never seen before.

-------- Original-Nachricht --------
> Datum: Fri, 29 Feb 2008 11:35:31 +0000
> Von: "Brecht Van Lommel" <brechtvanlommel at pandora.be>
> An: "bf-blender developers" <bf-committers at blender.org>
> Betreff: Re: [Bf-committers] point cache

> Hi,
> >> - Viewport/render levels: the point cache makes no distinction between
> viewport and render levels, and so when rendering with a different subsurf
> level, the point cache is reset. Also the physics modifier might have been
> disabled for the viewport in which case there is no data to use at all.
> This most obviously a problem for particles, but can affect any physics
> system.
> >> - An approach to this could be to have a separate render point cache.
> When rendering it would automatically simulate all previous frames. That
> might however be very slow. In principle you could also only do this in case
> it is really needed and the render mesh result is actually different from
> the viewport mesh. Also for renderfarms you would need a way to generate such
> a render point cache for all frames.

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