Shrink to Trim

[donest]

In the past I have used shrink to trim successfully, but I don't use it frequently. Now, I have a rather dense file that was created by digitizing. It is not a point cloud, but is a mesh. I can project curves onto the model, trim, move CVs, etc, But I really want to shrink the size of the file. When I use the trim tool to do this (data that is not needed anyway), there is no shrink to trim option, like I have used in the past. I have checked my plug in manager, and the box to enable it IS checked.  Any ideas?

[Nikki.schwaiger]

Hi,

the shrink to trim is only working on real surfaces like Nurbs but not on Meshes.

For a mesh you have to do like this:

https://knowledge.autodesk.com/community/screencast/e2a3cd30-8ac9-4004-b726-21cc00605edf

[donest]

It seems to be working now. One mistake that I made was to drag the trim tool over to a tab on the control panel. I do this for tools that I commonly use. Evidently, when I did it, I had not installed the plugin. The "shrink to trim" option is there on my palette, so I deleted the old trim tool from the Control Panel tab and dragged the new one over there. I think my understanding of the tool was in error as well. I thought that once you used Shrink to Trim and displayed the CVs, there would be no CVs on the part that has been deleted. I was wrong, they are still there, but the file IS smaller! Thanks for your response.

[Anonymous]

thanks for your help

[donest]

Maybe this will help to understand. The face on the left is the mesh (?) with the CVs turned on. Originally I had set the digitizing software to make a point (what turns out to be an XYZ intersection) every .009 inches. I wanted to be sure to capture as much detail as possible. The resulting file was exported to iges format. It was pretty big, and was about 870 spans by 870 spans. I reduced the number of spans a couple of times and ended up with 175 x 175. At least then I could grab CVs and move them, although difficult. When shaded, it's almost impossible, because grabbing a CV and then moving the cursor with RMB, it took several seconds for the CV to catch up to the cursor position. I discovered that without shading the model the CV would move a lot better, but not ideally. 

The second face is what the file looked like after trimming away the rest of the rectangle when shaded. Pretty "orange peel" looking. I then smoothed the face and manipulated CVs to get the 3rd face.

The image labeled "4" is what the mesh looks like from a Top view with the projected curve on surface that I used for trimming. Superimposed on that is the same mesh as "4", but from the side view.

[Nikki.schwaiger]

Hi,

we have to make the differents between Mesh and surfaces.

Mesh is a polygon file with normaly threeangular planar surfaces without CV's and spans.

Alias can simplify the Mesh and smooth it but you can't modify it like a surface. Normaly if you make a scan you get a Point cloud and from these points the system is creating a mesh (STL). This is what I cut in my video.

Normaly you make a revers modelling from the STL to create real surfaces (Nurbs or Bezier), typical for automotive. Some systems can do a automatic rebuild from the STL and you get Nurbs surfaces. These surfaces are close to the STL you can use them for an 1:1 copy but if you like to optimise some areas (like better highlights, etc) you get lost.

In your case you have a couple of surfaces (Nurbs) here you have to do a different way.

The shrink to trim tool is the first step which realy helps to remove the useless enlarge surfaces and the unused spans.

for the next step I prefer to use the tool Rebuild Surface here you can say reduce spans in a acceptible tolerance.

These two tools makes about 80% of the work automatical. The rest is hand made surface by surface.

You can also use the tool smooth with fixed edges for reducing the "Orange effect".
all of these tool helps you to clean it up without touching or showing a CV.

I dont know which graphic card are you use, but if Alias becomes very slow when you shade the surface you should raise the tolerance. I work with Quadro M4000 and I can use 0.001mm for a whole car without a big delay.

If you select fast in the tesselation instead of accurate it will help and the next thing use in the Anti Alias for the hardware 4x not 8x. You will not see a differnts but it speeds you graphic card.

I hope this may help

[donest · Accepted solution]

Yes, I suppose I used the wrong term. When I look at the results of my digitizing scan from the top view I see nothing but rectangles. Very fine rectangles depending on how often I instructed the machine to make points. You would think that those points are nothing but a point cloud, but when finished, I have the option to export the results in a number of different file formats. I think stl, dxf, and the one I use, which is iges. Because I can export to iges, I guess the file is actually  nurbs. 

In the past I have struggled to smooth that orange peel look because smoothing the surface usually means some loss of detail. So I smooth just once with minimal settings, reduce the number of spans, and then manually move CVs to make it look better. I have a dell precision T3600 work station with a Quadro K4000 and 16 gigs of memory.

I haven't tried the settings that you have suggested yet, but I'm sure they will help a lot. Thank You for all of your help.