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Question about Welding Primitives
Posted: 09 September 2012 08:56 AM   [ Ignore ]
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Is WELD the correct command to use when makinga composite shape from two or more primitives? Example: rectangular primitive with various spikes made from cone primitives inserted all over it’s surfaces. Say 1 rectangle, 15 cones inserted. Select all and click weld. Does that operation remove all the unseen polygons and parts and make it a contiguous whole with nothing “hiding” on the inside that has to be computed somewhere down the line?

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Posted: 09 September 2012 09:11 AM   [ Ignore ]   [ # 1 ]
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In a word, no.  Try it yourself.  I created a cube primitive, stuck a cone into it and used the Weld tool from Vertex Modelling.  The result is shown below.  You would need to use a different method, lining up points and target welding them I think.

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Posted: 09 September 2012 09:19 AM   [ Ignore ]   [ # 2 ]
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Thanks for the quick reply JimmyC_2009 - I thought I was approaching it wrong but wanted to verify - it just seems sooooo easy to do it that way. Is it preferable to NOT combine primitives then and, for the example project I mentioned, work with a single rectangle primitive ONLY, and manipulate surface polygons into the shapes I want (in this case spikes at random sizes, shapes and spacing)? Or, sliding the primitives together and as you suggest, wlding (target) points togother and deleting the parts that don’t fit when your done (the hidden parts)?

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Posted: 09 September 2012 09:38 AM   [ Ignore ]   [ # 3 ]
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A Boolean Union would do what you want to do easily, but it leaves very messy geometry at times, and I seldom ever use them.  It works great for one cone (see image), but for several it may make a complete mess.  Box modelling would probably be the easiest way to make a clean mesh, using extrude surface tools.

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Posted: 09 September 2012 09:49 AM   [ Ignore ]   [ # 4 ]
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Thanks again. You actually answered two questions I had with the comment about the boolean operation. I’ve noticed the tendency of that operation to spawn all kinds of interesting polygons and had wondered if there was a real reason behind that or if it’s just trading cleanliness for expediency. However, you could clean this type of image up, couldn’t you, by welding/combining individual polygons that you find un-necessary?

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Posted: 09 September 2012 10:00 AM   [ Ignore ]   [ # 5 ]
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Hexagon doesn’t really show you what a big mess it has made with Boolean operations, you need to import it into another app to see what is really there, it tends to look quite clean in Hex, but really isn’t.  Cleaning up the mesh after Booleans may be a problem too, depending on how bad it is.  It can create long nasty polys that DS and Poser don’t like at all.  At least that has been my experience.

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Posted: 09 September 2012 10:11 AM   [ Ignore ]   [ # 6 ]
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Basically it is much faster to use proper welding techniques then to try and fix booleans. Hexagon actually has some nice tools for adding necessary vertices, edges, etc… Ones that Blender for all of it’s tools doesn’t. The trick is to learn to use these tools. Once you do you will never look back to shortcuts of booleans. And yes, part of that is using the weld command, so on that you are on track smile

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