Trim to Plane

[GoBeavs]

Prehistory helped me on this earlier and I thought I would share...

Here was my problem: There is a part that I am scanning that I want to falsify by trimming off some of it's thickness.

I found this option first, but I could not close the model as seen below:



Then I just deleted everything below the plane I created, but now I'm left with this



I was then trying to extend the sides down to the trimming plane, and then fill the underside of the scan to make a watertight model. Prehistory then suggested this:

1. create your plane, then use the "Slice with Plane" tool to make a clean cut. Use Insert Intersection as the method, which will slice through all the triangles nicely. Then in selection mode (spacebar) select all triangles beneath the plane by using Shift + RClick, and choosing Select up to Plane. Hit Delete and you've got a nice clean boundary to start from.

2. Move the plane down below where you want the new bottom to be, by using RClick Edit > Edit Numerically, Translate along axis [some negative number].

3. Then, go into selection mode (spacebar), select the boundary vertices by using Shift + LClick, and choosing Select Boundary. Use the tool "Extrude Boundaries" to project those vertices to the plane below. Now you have a nice sidewall.

4. Finally, move the plane up to exactly where you want the new bottom to be, by using RClick Edit > Edit Numerically, Translate along axis [some positive number].

5. Then use the "Slice with Plane" tool to make a clean cut. Use Cap Inside as the method, which will slice through all the triangles and make a flat cap. Then in selection mode (spacebar) select all triangles beneath the plane by using Shift + RClick, and choosing Select Island. Hit Delete and you are done.

*If you are only wanting to cut upwards into the model, and you don't have any holes there, you an skip steps 1-4 and just do step 5

The first time I tried it, I messed up on the steps that I bolded, but then I reread it and it worked great as seen here:

[PW User]

The only thing I would add to this:
If you want to diminish the "wrinkled skirt" effect on the extrude boundaries command (it is caused by the lateral noise you have on the edge before extruding), you can create a closed boundary curve with a filter radius. The bigger the filter radius, the more it will diminish the wrinkles. If you make it too big, though, your radii will be affected. then you insert the boundary curve. the curve will then smooth out the wrinkles before you extrude to the plane.

Cheers!
Bernard

[GoBeavs]

The only thing I would add to this:
If you want to diminish the "wrinkled skirt" effect on the extrude boundaries command (it is caused by the lateral noise you have on the edge before extruding), you can create a closed boundary curve with a filter radius. The bigger the filter radius, the more it will diminish the wrinkles. If you make it too big, though, your radii will be affected. then you insert the boundary curve. the curve will then smooth out the wrinkles before you extrude to the plane.

Cheers!
Bernard

Great tip! Thanks

[GoBeavs]

Is this what you were talking about?







If so, I cant get the curve (or curve control points) to extrude.  Can you help from here please  :)

[prehistory]

Hi,

"Insert Curve" is a neat tool  You can use it to clean up the ragged edges of a model, or to make a smoother radius, or sharpen edges...  It basically takes the polygons and forces them to rebuild themselves to fit to the curve.  So you get a nice strip of rebuilt clean triangles near that curve. 

So bmunger wants you to use the insert curve tool to clean and rebuild the triangles nicely before extruding them using the method provided originally.  You should get a smoother result.  Just be careful when you first create the boundary curve.  Set the filter radius high enough to smooth out the perimeter, but not so high that the corners are lost!  When the golden curve looks the way you want it, click Done.

V 10.1.17

[PW User]

Hello,

Prehistory is right. The trick is to first "clean up" the edge of your scan using the smoothing radius of the boundary curve.

The rest of the process to extend your scan to a plane stays the same.

In you image, look in the dialog zone, you have a value of 0.5 for the smoothing radius... you need to play with that value to smooth the ragged edges in for the normal and tangential direction. The tangantial direction is not so important for this technique, but the normal direction smoothing is certainly the one that will remove the "wrinkled skirt" effect.

Note that you cannot extrude using the curve... the curve is only used to smooth the edge before extruding using the boundary vertices (the process YOU explained at the start of this thread, and very well too!)

Regards,
Bernard

[Homer-Jay]

i love this post, it's the second time i've used it