subtraction operation

All,

I will look into this for the next release. Even though I am pretty happy with the boolean operations they could always improve.

Richard

Hi everybody !

I’ve tested a very basic operation… I just want sustract an cube to a sphere… uhm… to make a demi-sphere <!– s;-) –><img src="{SMILIES_PATH}/icon_e_wink.gif" alt="" title="Wink" /><!– s;-) –>

I’m very suprised to see the result. There are some nasty points. So, i’ve tried to do the same operation with other modelers (Truespace, amapi, Milkshake3d). I’ve not this problem !

Do you know where is my error ? May be this is not the best method to do this with 3dc ?

Thanks !

Many thanks for your answers….

Oups, sorry for the mistake about MilkShake, this must be another modeler. (Moray i’m thinking an older Modeler). In fact this was the first time that i must correct this operation by hand. I don’t know if gmax do the same thing.

I believe that the basic implementation is the same everywhere. Booleans always create extra faces/points/edges. This is one of the general complaints of boolean operations.

Also, I don’t believe that Milkshape3D has booleans.

Richard

Try changing the latitude of the sphere from 12 to 13 – so it andquot;cutsandquot; on a andquot;known lineandquot;

another way to get this half ball….

(alt) group select all the points below the line where you want to cut and trim selection…..

(still will only cut on lines though, so for a half sphere you still need to alter the number of latitudes to an odd number)

What Truespace does is it andquot;hidesandquot; the edges it creates since it can render concave faces (3dc can’t). These additional edges are still stored internally and are just not shown in a wireframe view. But if you export to DirectX you will find that they are there. It is possible that they produce andquot;lessandquot; edges, but if you look through the ‘net you will find that one of the common complaints about boolean operations is that they create too many new faces/points/edges.

One common andquot;solutionandquot; for this issue is to use face reduction (such as the andquot;reduceandquot; operation) to clean up the edges.

Richard

OK, point taken, just trying to help……. :-[

Alex,

There are a couple of differnet issues here. The example you show is not a particularly good one since it doesn’t produce any concave polygons. My statement about Truespace is correct, but this example doesn’t demonstrate it. You would need to try a different example.

This particular example does not show 3DC’s boolean operation in the best light. What 3DC does is it triangulates the objects involved so there are no concave or non-planar faces. Then 3DC does the boolean operation and de-triangulates. In this case this results in a few extra edges.

Richard

Nice one Alex <!– s:) –><img src="{SMILIES_PATH}/icon_e_smile.gif" alt="" title="Smile" /><!– s:) –>

Works for me – although I don’t think you need step 1 ( the first triangulation). Also on a couple of my tests I have had to repeat steps 3 and 4 a couple of times…..