Network surf tangency continuity

unhandled

#1

Inside Rhino, network surf with tangency or curvature continuity is easy to do. However, is it possible in Grasshopper? The Grasshopper node only has U, V, and C (continuity level) sliders available. It really seems like the Network Surf node needs a fourth input, one for any surfaces that the U or V curves come from.

Here’s the issue:
In Rhino, use the three black curves and the red surface to make a smooth network surface as shown in step 2. Edge surf does not work properly, as you can see from the zebra analysis. Network surf with only position checked also does not make a smooth surface. Network surf with tangency or curvature continuity makes better surfaces. Curvature continuity makes the best surface in looking at the sharp valley zebra curves.

Can Grasshopper create network surfs with tangency or curvature continuity?

Because the GH network surf node only takes curves as inputs, it does not seem like there’s a way to have GH use a surface edge. The minute you break out a surface edge from the surface, it becomes just a curve and detached from the surface curvature knowledge.

Any help? I found this forum post, but it never seems to really answer the issue: Connecting tangent surface creating with network surface command

Thanks,
Matt



GH forum NetworkSurf continuity issue 180613.3dm (84.7 KB)

GH forum NetworkSurf continuity issue 180613.gh (4.7 KB)


(Michael Pryor) #2

These are the options available for network surface in Rhinocommon.

netSrf.gh (9.6 KB)


#3

Hello,

the continuity parameter just sets the internal continuity, when the result yields more than one surface. Is it useful? No its not. Grasshopper and Dynamo both are missing strong surface modelling features which makes it very difficult to apply it in any useful modelling szenario. Unless you have access to a stronger surface library you are forced to do workarounds all over the place with very limited success. In Rhinocommon v6 there is a Blend Surface command, the more useful feature: Match surface is not in there yet. Maybe you work with that.
Furthermore, if you create bad initial conditions, even the best algorithm will have trouble in matching continuity.
So as a conclusion: Don‘t do free form surface modelling inside gh. its not the right tool for it.


#4

Is it possible to program additional parameters to the Grasshopper Network Surf command to have an additional input node (or two)?. The additional input node would be for surfaces whose edge curves are the U or V curves already plugged into that network surf command. It seems like Grasshopper simply needs to realize that some of the curves that you are using to create the network surf came from other surfaces and were not isolated curves.

I’m simply comparing the process to Rhino. In Rhino, you only click on the curves you want, but if you click on a surface (for which you have already extracted an edge curve) then Rhino will pop up the mini-dialog box asking you to pick whether you want to choose the curve or the surface edge. All you do is choose the surface edge rather than the extracted curve and you get the tangency continuity.