Subject:
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Re: Latest BFC Spec?
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Newsgroups:
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lugnet.cad.dev
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Date:
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Sat, 22 Mar 2003 00:26:29 GMT
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Viewed:
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614 times
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In lugnet.cad.dev, Ross Crawford wrote:
> What if file has NOCLIP, and subfile has CLIP (with or without accompanying
> NOCLIP)? Couldn't that become confusing?
During the rendering process, it is necessary to keep track of both the
'accumulated clip-state' and the 'local clip-state'. The accumulated
clip-state is logically equivalent to boolean ANDing the local clip-states
of all the parent files. As each file is rendered, it keeps track of its
own local clip-state, which does not affect the parent file. BFC-ing is
only allowed if both the accumulated and local clip-states are CLIP (among
other requirements).
> Should it automagically revert back
> to NOCLIP when the subfile is finished?
Yes, and if the spec doesn't say this explicitly, it probably should.
The pseudo-code in the "Rendering Processing" specifies this behavior. The
(recursive) rendering procedure RenderFile is called for each (sub)file in
the current model. RenderFile receives an input parameter AccumClip, which
is boolean -- true for clip, false for noclip; AccumClip represents the
accumulated clipping state; it is only true if all parent files are
CERTIFIED and (currently) set to CLIP. LocalClip represents the current
clipping state of the local file. The core pseudo-code for rendering
polygons is:
10 If AccumClip and LocalClip And (Certified is TRUE) Then
6 If BFC(Command, AccumTransformMatrix, Winding) Then
4 Render Command
4 Else
4 Don't render Command
4 Else
4 Render Command
4 End If
Steve
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Message is in Reply To:
 | | Re: Latest BFC Spec?
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| (...) What if file has NOCLIP, and subfile has CLIP (with or without accompanying NOCLIP)? Couldn't that become confusing? Should it automagically revert back to NOCLIP when the subfile is finished? ROSCO (21 years ago, 13-Mar-03, to lugnet.cad.dev)
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