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Here is a car brake disc Im working on:enter image description here

so I decided to use boolean mdifier to make the samll holes(one side),but it just caused the other half to disappear: enter image description here after some experiment，it seems that boolean mod doesnt support unclosed mesh or seperated mesh,and also cant treat closed mesh as holow instead of solid,and when applys to smooth surface it looks like this:

enter image description here

only way I thought to make hole on cured smooth surface without too much subdivision is to use edge split,and then I find out edge split doesnt support vertex gruop which is kind of inconvenient. So is it possible to ask developer to add these feather or is there better ways?

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  • $\begingroup$ Yes booleans operations are meant on "solid" objects. To understand how you could do, you need to show the state previous to the boolean operation (or upload at least that part of the model). For the other issue I can't understand fully: maybe batter to open another question, since it is unrelated. $\endgroup$
    – m.ardito
    Commented Jan 22, 2017 at 8:54
  • $\begingroup$ thanks for replying,I went back trying to recreate the scene and find out the problem is gone,I thought maybe its that previously I used too many unsorted modifiers that caused boolean to oversee part of the seperate mesh(island). $\endgroup$
    – user34102
    Commented Jan 23, 2017 at 8:30
  • $\begingroup$ for another problem,i added a gif to my post. $\endgroup$
    – user34102
    Commented Jan 23, 2017 at 8:45
  • $\begingroup$ i cant figure out a way to use boolean on smooth surface,doesnt matter the order of boolean and subdiv,I think this should be something more complex,so I just decided to move on to new methods. $\endgroup$
    – user34102
    Commented Jan 23, 2017 at 8:50

2 Answers 2

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I expand my comments above, to post some example image. I still think it's a matter of mesh density:

To better visually describe I exagerated size of the diff meshes, but this is the overall setup:

enter image description here

this is how a subdiv level of 2 on a standard UV sphere, in boolean diff with a cube, enough subdivided and extruded, then hidden. Still, you see some artifact on the hole edge.

I tried a gif animation showing the effect of changing settings, but due to color banding it gets lost... so here is a rendered comparison with subdiv 0,1,2, and 4 (enough in this example)

enter image description here

As said above I can't show you here, but even "moving around" the sphere doesn't show artifacts (or they are much more subtle) in the viewport, and the same goes in the render.

I don't know how better you can solve this, but using much higher resolution on the edges of the subctraction, at least, will help blender to find a "smooth" setup for normals of geometry around that area...

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  • $\begingroup$ Thank you so much for the info! Ive tried more subdivs before,but the result was not good,now I realize its because I was cutting round holes,and round shape doesnt match the topology being cutted.So it takes both topo density and topo shape to make it look good.Idk if the modifier can be improved,cause I was hoping to bring it to game engine.I post another picture as answer below. $\endgroup$
    – user34102
    Commented Jan 23, 2017 at 11:07
  • $\begingroup$ Dont know how you record gif,but I use this very very handy software called gifcam, $\endgroup$
    – user34102
    Commented Jan 23, 2017 at 11:23
  • $\begingroup$ I use this cockos.com/licecap , which ids gpl, and works also on linux+wine. but gifs are their own limitation (256 color palette, no play controls), sometimes they work but not always... $\endgroup$
    – m.ardito
    Commented Jan 23, 2017 at 11:45
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A comparison for methods to cut holes.

From left to right:

inset-extrude-crease;

inset-extrude-edge split;

boolean topology shape match;

boolean topology shape not match;

enter image description here Different methods have different cons and pros,need to chose one that served your workflow best.

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