Booleans deletes object

# 1 08-12-2009 , 04:28 PM

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Hello again.

I am still messing around with my boat model. I wanted to use a boolean to cut a round hole in the model, but when I selctd the round object and use a boolean the whole model disappear.

Why? How do I fix this?

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# 2 08-12-2009 , 09:27 PM

The thin red line
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Sellect the boat first then the tube while holding the shift key down then go to boolean differance, then you might want to clean up the mesh see ctbram has done some work in WIP...........dave

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# 3 08-12-2009 , 09:35 PM

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I did a smooth on the model and found some funky vertices and cleaned them up. So smooth was a good tool to find the errors.

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# 4 09-12-2009 , 03:55 PM

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There are a number of things that can cause the disappearing geometry...

1. The surfaces must completely intersect

2. The surface normals must match direction. You can test this by turning off two-sided lighting (its under the lighting menu)

3. The geometry must by manifold. You can check for and correct bad geometry by running the clean up under the mesh options.

Those are the main things to check. Also run a test by creating two poly cylinders and just scale one down and then make sure boolean works on them.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

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# 5 09-12-2009 , 04:40 PM

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I think I am using the cleanup tool wrong cause either it does nothing or it collapses the whole model. So in the end smoothing and looking for strange bumps was the best way for me to find extra vertices.

This is perhaps more of a philosophical question, but do models have to be perfect or will they render just as good if one piles up a number of different "boxes" that intersect? I mean you could make a T-shape with extrudes that are connected or simply stacking two qubes? Does it matter in the end? Assuming you will not animate the object?

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# 6 10-12-2009 , 12:28 AM

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To answer your question a model does not need to be a single unified piece of geometry like a single perfectly joined polygon.

Here is a model that I made that is basically polygon boxes and other primitive objects all stuck into each other. This is common for these type of models (see Kurt B's assault mech tut).

https://srv01.simply3dworld.com/showt...threadid=25308

That being said the topology should be clean (no floating verts, non-manifold geometry, co-planar faces, faces with zero surface area, etc. These are the things that cause Maya's tools to malfunction and others done the pipeline to want to put a hit contract out on you!

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 10-12-2009 at 12:32 AM.

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# 7 10-12-2009 , 05:54 AM

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Ok, it does not need to be one perfect polygon. Is there some guidelines anywhere about when and why it should be one polygon and when is should not?

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# 8 10-12-2009 , 01:12 PM

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Not really. It depends on your clients or your own needs. As someone else said if there are no written requirements then it all really comes down to doing it however you can to get results you or your client are happy with.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

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# 9 10-12-2009 , 06:17 PM

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Well as a student and learner I have no clients to care about so I am just trying to get used to working as correctly and efficient as I can for the future.

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# 10 11-12-2009 , 02:50 AM

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Booleans are temperamental. Some times even perfect geometry will error. It's just the luck of the draw. One thing to always check, is the normal direction. Booleans are very picky about them.

Also, if the selected boolean operation doesn't work, try the other two. Sometimes they give unpredictable results.

The quickest way usually is to just use the split poly tool, and extrude the polys afterwards. Doing this will also always give you better geometry than booleans, which will always create n-sided polys.

Imagination is more important than knowledge.

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Booleans deletes object

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