Geonovast

Blender Model Clipping... Is it ok?

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I'll preface this by saying that up until very recently, all of my 3D modelling experience has been in Sketchup for the purpose of 3D printing.  When you're modelling for printing, you ideally want to remove ALL internal lines/faces, otherwise it can cause undesirable effects when slicing.

It's also fairly easy to do in Sketchup.  I'm finding it's not so straightforward in Blender, so it's becoming time consuming.  It's just been habit, but now I'm wondering if I should bother.

So say I've got a box.  I want a pipe going into the box at a wonky angle.

BoxTube1.png

Can I leave it like this?

BoxTube2.png

Or should I clean it up like this, which is what I'm used to doing?

BoxTube3.png

 

What I'm actually working on that made me ask:

Spoiler

BlenderModelClipping.png

 

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Not sure if KSP makes a physics mess of things if you do, not that experienced of a modder, me

On the other hand though you can avoid the problem alltogether if you take a couple minutes to figure out the boolean tools Blender provides to smash your meshes together into a single one clipping any excess

Blender contains tools for literally anything and youtube provides many tutorials such as this one: https://youtu.be/Vf2M1bxZYk0

 

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Thanks @hoioh.

 

I had seen the boolean stuff in tutorials before on doing that, but had also seen that it wasn't a good idea for some reason.  Something about it increasing triangle count.  They all wanted me to use the knife tool, which isn't precise and I can't seem to operate anyway.

Right now I'm using 2.71 since that was the version being used in the tutorial I followed.  It's an older tutorial, but seemed the most relevant since there aren't a whole lot of modern ones out there.  I did manage to get a version of the Bool Tool add-on that works, and I think I got it doing what I need.   So I should be good now.  Hopefully.

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The knife tool is much easier to operate when combined with the shift key, that allows you vut straight lines

When you are really attempting to be as low poly as possible then yeah, it will improve things a bit over the course of 50 odd parts, but KSP doesn't have a really big problem with poly count, so who cares

I just fiddle with it until I have a model which is easy to texture

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Disclaimer - I'm far from an expert on this. With that in mind on all my models I don't worry about clipping. I do remove extra faces - in the middle picture of your OP I would remove the inside cylinder end and slide the remaining face ends closer to the cube surface but wouldn't worry about getting too close. In fact I have found that if I try to get things flush - no clipping - I sometimes get sparkles in game when moving around. One situation I don't worry about flush edges is when I separate one mesh into two - cylinders are a good example - if you smooth them with the end caps it doesn't look very good so after I have my cylinder where I want it I separate the end caps to a different mesh and the smoothing works much better -  but the edges are dups so exactly the same (or close enough not to matter - not clear on the inner workings of Blender) and I don't see the sparkels.

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@Geonovast

There is no issue in Blender/Unity from self-clipping geometry as far as physics are concerned.  Clip away.  Same thing with using multiple colliders for a single part -- they can intersect and clip as much as you need.

Now, hidden faces are often still rendered to some degree, at the very least a culling/depth test on the fragment, so they do add some minor overhead to rendering (fill-rate based), and should be avoided and minimized wherever possible.

Also note that it is often bad to use the Blender Boolean tool (it does have uses, but simple intersections are not it).  The meshes created from cutting/joining are so far from optimal, they make me cry (so many useless and skinny triangles created).  Much simpler to intersect the geometry and deal with a bit of extra overdraw than to render dozens of un-needed triangles.

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5 minutes ago, Shadowmage said:

Also note that it is often bad to use the Blender Boolean tool (it does have uses, but simple intersections are not it).  The meshes created from cutting/joining are so far from optimal, they make me cry (so many useless and skinny triangles created).  Much simpler to intersect the geometry and deal with a bit of extra overdraw than to render dozens of un-needed triangles.

I had seen quite a few mentions of using the Boolean tool not being the best.  As much as I hate clipping, even in this, some of the situations like I have up above is just too much work.

I've actually been playing lately instead of dealing with this, but I'll be in DC all next week without my main install, so I'll probably do some blendering in the hotel while I'm away.

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