Subject:
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Re: Glass... to BFC or not to BFC?
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Newsgroups:
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lugnet.cad.dev
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Date:
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Fri, 29 Nov 2002 19:09:50 GMT
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Viewed:
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505 times
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In lugnet.cad.dev, Erik Olson wrote:
> In lugnet.cad.dev, Tony Hafner writes:
> > When authoring "glass" parts, should I include BFC statements?
> >
> > It seems like we wouldn't want to cull because all surfaces should be
> > visible from any direction. On the other hand, BFC is a performance
> > optimization and transparent surfaces are generally a bigger perf hit than
> > other surfaces.
>
> They require a different approach to optimization - visibility culling, not
> backface culling.
Right. For some renderers.
Basically, in standard LDraw renderers, the backside surfaces can still
be culled, because multiple layers of transparent surfaces look the same
as a single layer.
In renderers that produce darker/more opaque areas for multiple layers
of transparents, the backsides need to be kept.
> You're right in thinking they should not be BFC.
Actually, they still should be BFC'ed. Several reasons: some renderers
can still cull the transparent backsides, people might use the part with
an opaque color value, and BFC'ing the file ensures that the polygons
are cleanly wrapped. That last one is useful for other things besides
BFC processing.
Most glass parts can be built from the box.dat primitive, which I
believe is already BFC'ed.
Steve
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Message has 1 Reply:
 | | Re: Glass... to BFC or not to BFC?
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| Doesn't the BFC "spec" mention transparency? The renderer can easily tell when something is transparent, and do BFC processing (or lack thereof) appropriately. This is necessary for correct handling of standard parts that are sometimes transparent, (...) (22 years ago, 30-Nov-02, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: Glass... to BFC or not to BFC?
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| (...) They require a different approach to optimization - visibility culling, not backface culling. You're right in thinking they should not be BFC. The exception I think might be a full box - which gets composited twice in a polygon system like (...) (22 years ago, 25-Nov-02, to lugnet.cad.dev)
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