Newbie - How to create solid from an extrusion and curve 90 deg to each other?

Hi Simon,
The Direction command (Dir) gives you the option to flip the normals. When you Join all of the surfaces, Rhino figures out inside from outside and rationalizes all of the normals so they are all facing outward in a valid, closed polysurface.
Glad it’s working out for you!
Best regards,Doug

Perfect, thanks again.

Loving Rhino for it’s abilities to manage complexities, having a hell of a time with the basics… lot’s of learning to be done.

Cheers

Hi V8Goose - for the sake of variety, here’s a different approach that tries to keep the character of the straight/extruded shapes intact as they sweep around the end arc:

surface between extrusions_PG.3dm (140.2 KB)

Sweep1. working up from blue to red, each sweep on the edge of the surface below. Use “Align with Surface” in the Style dropdown.

-Pascal

Wow, thanks Pascal…

This is how I envisioned a command working and I’ve successfully applied it.

It machined very well.

Thank you!

This is how I would do this. Mostly sweep 1 rail. Then project curves onto the top surface. Sweep 2 rail the helper cap surface. Then trim it back with a circular curve. Then redo the top swept surface this time as sweep 2 rails. This method does away with problematic surfaces with singularities (stacked cv’s).

On the other hand, singularities are only problematic if they are problematic - I don’t see any problem in this case, do you?

-Pascal

I have no idea in this case. Small surface ripples and surface continuity breaks around the singularity point. Combined with an increased risk of offset and shell failures. Has taught me that they’re to be avoided. I’ve figured out enough approaches. That it takes very little time to model around them. Dealing with them in fillets can be more time consuming. Even then it just requires advanced planning of the topology.

Stratosfear, can you show us your isocurves and explain more how you do not get a singularity in your green surface?

How does your Zebra look across that D cap? I have a feeling it would look a little funny where the singularities would have been in the D surface if you just did a blend. Are you saying trimmed surfaces are ‘better’ that untrimmed ones as far as reliability goes? I still haven’t been able to duplicate what you did. I get lost at projecting curves onto top surface. Which curves, which surface?

Trimmed surfaces are always better than untrimmed ones with singularity points. I did make some changes to existing geometry. Tangent matching the surfaces adjacent to the top cap.

This shows the problem with singularity surfaces. There’s a noticeable ripple and break in tangency. The greater the number of stacked cv’s the worse it becomes. The tangency break will often result in shell and thickening failures.

Hi Jason,

It should be noted that zebra analysis uses a mesh to visualise the surface normal continuities. Such a singularity results in a dense mesh around it, often with high aspect ratios of the mesh faces. The resulting artifacts in the rendering are not an accurate depiction of the surface normal continuities perse.

-Willem

You are right depending on the mesh setting this can appear much worse than it really is. However the real issue comes when shelling and thickening. Where the the offset of the singularity surface will self intersect and create multiple naked edges.

1 Like

I am sorry but I am still a bit lost. My goal would be to turn the curves in this file into a closed polysurface with all surface edges joined tangentally and without singularities. I was hoping your methods would help me. I am basically a beginner and I still don’t see how you extended the top cap of the OP’s object (with square corners on the extension) such that the semicircle is on the surface of the extension.

test.3dm (39.5 KB)

Is there a way to to create my desired closed polysurface from the curves in my file?

Thanks for all the help so far!

This is the kind of singularity and non-tangental stuff I’ve have been able to achieve:

This is the topology approach I would take for this kind of form. I just figured out how to do this about a year ago. I speed modeled it and turned out water tight without the need for additional surface knots. I must be getting better. I had to add additional curves and clean up the existing ones to make everything bezier. In this case degree 3, 4 points.

I used the following commands: surface from edge curves, surface match, surface split at isocurve, surface shrink, surface blend. surface rebuild, curve duplicate edge, curve pullback, surface trim. It would take me forever to write a proper tutorial for this. Unfortunately I don’t have a capture card either. I hope this is helpful and gives you some insight.

You might give this a shot with t-splines. It should be easier and faster depending on your skill level. There are downsides to using t-splines. It just depends on what you are doing with the finished form.

1 Like

Thanks, I will make a serious attempt to follow your template, it does generally make sense to me.

I have 7 days left on my t-splines trial but I have lost faith in learning an easy way to build t-spline solids that pass through defined curve networks. But, I love t-splines for more loosely defined organic shapes!

Again, thanks for your help!

Finally got your idea on OP’s Dcap (finially figured out had to extend long edges of top cap over Dcap and then project onto top conic surface, then 2 rail top cap end curve along those, then trim that new surface to top edge of top conic, then delete conic and remake top conic with 2 rails) Yeah, and it shells nicely :smile:
:

Well done. Your modeling will take a big a step forward now. Here’s another way I deal with singularities. I use extract iso curves and projected curves to trim out the singularity with a four sided opening. Then patch in that hole with a surface from edge curves.

Great, that is cool.

In a pinch I would just create a small sphere at the singularity, trimmed the sphere out of the surface and then patched the surface hole somehow.

Now I have more and better ways, thanks!