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In lugnet.cad.dat.parts.primitives, Chris Dee wrote:
> In lugnet.cad.dat.parts.primitives, Steve Bliss writes:
> > Actually, for rounded elements, it's almost always[1] preferable to use
> > primitives. That way, programs that do primitives substitution can replace
> > the polygonal primitive with a true round object.
>
> There are some complex curved parts (e.g. most of the minifig headwear, the
> minifig arm I'm working on right now, some wheels) where some regions can be
> represented by the regular cyli, disc, cyls, cyls2 primitives, but there will
> be regions that no amount of twisting or stretching can handle - and these have
> do be done as polygons, and cannot be substituted. Then there will be gaps !
Very true. In some cases (like the minifig arms), is it better to go
with an all-polygon approach, or to use primitives as much as possible
and fill in the rest with polygons?
> Also, where any rectilinear region intersects with a curved region the
> intersection edge should be different when rendered with the 16-agon
> primitives, to when rendered with substituted "true" curved surfaces. Such
> support is generally not written into the DAT file.
When filling in around a hole in a flat surface, one should 'always' use
the X-4ndis.dat primitives. These are the only primitives that
'convert' from a round edge to a rectilinear edge.
In other cases, overlap can be written into the part. Or should we be
thinking about a 'phantom' primitive, that would serve to inform
primitive-substitutors that there are polygons adjoining a curved
surface? Something like:
1 16 0 0 0 10 0 0 0 1 0 0 0 10 ring4.dat
1 16 0 0 0 10 0 0 0 1 0 0 0 10 ring4go.dat
Where the real file ring4go.dat is empty, but is a signal to
primitive-substitutors that the issue of gaps on the outside of the
primitive need to be addressed.
This could also be done as a meta-statement:
0 FILLGAPS OUTER
1 16 0 0 0 10 0 0 0 1 0 0 0 10 ring4.dat
Where the FILLGAPS meta-statement would direct the primitive-substitutor
to generate surface around the outside of the following primitive to
fill any gaps between the true round surface and LDraw's polygonal
approximation.
Steve
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Message has 1 Reply:
 | | Re: ring 3 to 5
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| (...) have (...) Are you suggesting that there is (should be) a command to prevent primitive substitution, or that the primitive should be inlined? (...) Agreed. What I was more thinking of is the situation (in the minifig arm) where one region is (...) (22 years ago, 4-May-02, to lugnet.cad.dat.parts.primitives)
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Message is in Reply To:
| | Re: ring 3 to 5
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| (...) There are some complex curved parts (e.g. most of the minifig headwear, the minifig arm I'm working on right now, some wheels) where some regions can be represented by the regular cyli, disc, cyls, cyls2 primitives, but there will be regions (...) (22 years ago, 3-May-02, to lugnet.cad.dat.parts.primitives)
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