trimming problem in rhino

[fede]

Not the first time it happens...
I'm trying to trim a surface that has been previously trimmed to put strakes on it.
I'm just trying do "drill" a circular hole for the bow trust.
I get the trim ok but then the surface gets creazy...the wireframe looks good but the shaded surface looks orrible.
Pics attached pretrim post trim and post trim with wireframe looking good.

[Tim B]

which version of Rhino are you using? It is possible (though fairly unlikely) that it is a software glitch

On a more mathematical note, try to keep to single, untrimmed surfaces. They are much easier to handle, and much easier to understand. Do you really need to split the surface to add the strakes?. It is easier not to worry about the strakes (which you can specify later) and then use split to split the surface for the bow-thrusters.

What I have been doing recently is to use a single surface for each side of a (fair) hull for yachts. For powerboats, you need the change in geometry, so use two surfaces. The flat on the chine can be made using the surface control point weight function. This is a very powerful method, and with practice will give smooth, fair hulls.

Tim B.

[CGN]

mesh resolution, try setting your resolution on "smooth and slower" and see what happens. i think is only problem of the resolution of the mesh, i don't think is nothing wrong with the surface itself, but you never know.....

[SailDesign]

First of all, check to see which surfaces are "Bad". You can sometimes go back in and rebuild these easily. I have had good success with taking out the offending surface and shrinking it (ShrinkTrimmedSurface), detaching the trimj, then retrimming with a good trim-line. Sounds tedious, becomes second nature....
I have done anumber of boats with spray-rails/strakes like yours, and have not had trouble.
Also, make sure that the "hole" for the bow-thruster stays clear of any surface ends/intersections. Rhino2 can screw up if they are too close, and Rh3 is not much better. Just nudge 'em a hair off.
Steve

[fede]

I made it!
I suspect the problem was that I was trying to trim a surface previuosly trimmed, joined with another surface and then exploded.
I always keep a lot of incremental saves in my folder, went back before joining surfaces did copy the surface I needed pasted into the current file version all was ok.
As always, thanks for your help!