LEGO Elements/Parts : 5974


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Subject:	Re: Overlapping primitives - a reason to Hold a part?
Newsgroups:	lugnet.cad.dat.parts
Date:	Sun, 16 Jul 2006 12:53:46 GMT
Viewed:	3031 times

In lugnet.cad.dat.parts, Timothy Gould wrote:

In lugnet.cad.dat.parts, Travis Cobbs wrote:

In lugnet.cad.dat.parts, William Howard wrote:

What is the policy on overlapping primitives in a part? Is it OK? Is it frowned upon? Is it accepted as the norm? Is it only accepted under exceptional circumstances? It excessive over-lapping of primitives (or quads/tris) a reason to Hold a part? Is any over-lapping (beyond the exceptional) a reason to Hold the part?

I don’t know what the policy is (or if there is one), but I will point out that it will likely cause artifacts in any transparent parts in any viewer that supports blended transparency (such as LDView). The overlapping sections will get drawn twice, making them a noticeably different shade.

Here’s an example of a quad overlapping a disc drawn in transparent gray:

--Travis

Ahhh. Very good point. I think you’d get problems in povray too.

Tim

If you post a hold vote for all parts contain a overlaping between a primitive and a quad or triangle, you must post a hold vote for all parts with contain a stud (ex : all brick !!!). Because all studs are overlaping with quad or box. It is necessary to make the difference with an excessive overlapping (bad use of primitive and quad) and a necessary overlapping for the check returned by the part. In your example, it’s easy to replace by 4-4cyli and 1-4ndis. But in a real parts it’s different. You still have no possibility of assembling correctly a primitive with the remainder of the part, either you not used not of primitive! Else you must create a new primitive for only one part used !!! You must post a hold vote only if you can replace a bad quad and/or primitive by one other better part/or primitive. (ex: replace box5 by box4-1).

Message has 2 Replies:

		Re: Overlapping primitives - a reason to Hold a part?
(...) I may be misunderstanding you here but if it comes to the difference between a part having less primitives or a part displaying correctly I would always encourage displaying correctly. We don't use the Ldraw system to save computer memory, we (...) (18 years ago, 16-Jul-06, to lugnet.cad.dat.parts, FTX)

		Re: Overlapping primitives - a reason to Hold a part?
(...) First of all, you're right about the fact that there's no hole in the surface under studs, and this technically results in incorrect rendering. However, it's not something that people notice. Additionally, the missing hole under studs is (...) (18 years ago, 17-Jul-06, to lugnet.cad.dat.parts, FTX)

Message is in Reply To:

		Re: Overlapping primitives - a reason to Hold a part?
(...) Ahhh. Very good point. I think you'd get problems in povray too. Tim (18 years ago, 16-Jul-06, to lugnet.cad.dat.parts, FTX)

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