Surface patch wish


#1

I would really love to see the patch command work for conditions like this. Would it be possible to assign the isocurves to align with at least two specified surfaces? If I could achieve tangency to least two of the surfaces I could trim out and patch in the rest.


#2

Hi Stratosfear,

For an object like this I would suggest to use T-Splines. With Rhino you might be successful when you put in a lot of effort. However when the shape had to be edited you have to reconnect all surfaces again with proper continuity. That is very time consuming compared to using T-Splines.


(Willem Derks) #3

Hi Jason

First I suggest to see if adding curves to the input for the patch command gives better results.
A route could be to first extract isocurves from the adjacent surfaces. These iso-curve scan be used to create blends: blend from one isocurve to an opposite on another surface.
That way you can create a guiding lattice of curves to be used as extra input on the patch command
Hope my wording is clear enough, else let me know.

Also have a look at this post demonstrating the possibilities of the plug-in VSR Shape Modeling 2.0:

HTH
-Willem


(Pascal Golay) #4

Hi Stratosfear- you can use the Starting Surface feature in some cases to force a structure onto Patch. In this case it looks like it might not be easy though. The way Patch works is it cooks up a best fit ( but oversized) plane through the inputs and uses the plane orient the UV and adds the number of spans etc. If you orient a plane the way you want, it can be used to set the isocurve directions for Patch. You can also use more complex surfaces as Starting Surfaces but if it is other than a degree 1 by 1 or a plane, the Starting Surface structure as well as orientation will be used by Patch - i.e. you will not get to set Spans, these will be taken from the Starting Surface. You will probably want to set ‘Pull’ to zero in most cases so that the starter does not directly influence the shape, only structure and orientation.

-Pascal


#5

Thank you all for your input.
I’ve tried t-splines for this model in the past and finished result is just too lumpy for my liking.
I’ve tried multi blend in VSR for a similar 5 sided blend and the results were very good. I see there is a new control option for the split position. I might have to give that another try if I can.
What I wish patch would do is generate two surfaces that are curvature continuous at the split and tangent to all the input surfaces. I know even if I build a bunch of control curves and play around with number of control spans and weight. I still won’t achieve what I need.
It would be great if two rail sweep worked like surface from edge curves but with tangency control. I have managed to come up with an acceptable result after rebuilding and re-matching the surfaces numerous times. Project curves loose was very helpful.

I’m really amazed that this still such a difficult form to model.