Difficulties using ‘subtract’ operation

Just looking through some old forum topics and I thought I’d better update this one!

I rarely have problems now with subtract – most likely at that stage I was inexperienced in using the operations – I was using merge too much and extrude not enough.

Some problems can occur if an object isn’t solid. Though a lot of advice on this forum is to triangluate or optimise an object before using subtract, I find that as long as you orient and construct your objects / primitives accurately, you get an excellent result with the minimum of unwanted extra edges and points.

It’s well worth ‘tidying up’ your object immediately after your subtraction by removing these extra edges and points. If you come to extrude or merge in the future you may get small (or large) errors… and anyway, it’s always a good discipline to remove unnecessary points!


I am trying to use the subtract operation to ‘cut away’ part of a fairly complex shape (I say fairly as it’s only a cylinder combined with a cube to form a sort of arch shape)

I have cut away part of another cube primitive using a cylinder to form a ‘mould’ with which to cut away part of my ‘arch’ shape.

What happens when I perform the operation is that I get unexpected shapes and faces appearing and not the smooth cut away that I am after.

I have tried using triangulate to improve the accuracy but to no avail in this instance (this has worked before for me)

I have tried to find info in the help files or tips on the internet but so far I have not found the answer – does anyone know any tips to this and similar problems.

I am using 3DCP 4.3 – is this operation better in 5?

Try using the andquot;Optimize Object Geometryandquot; operation, then the andquot;Solidify Selectionandquot; operation to both objects. The object you are subtracting from, and the object you are subtracting with, then do the boolean subtract operation.
Sometimes the Optimize Object Geometry operation will change the colors of your surfaces, so be prepared.
I usually do these two operations before applying any colors/textures.

Ahh. Merge. I can see that being a major problem. The results could well be a mess. If your object has interior faces then it really isn’t andquot;solidandquot;.


yep, sometimes the results can be a mess!


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