Hi, I am following Level 1 Training (Chapter 11) and run into an issue with using Blend Surface. Basically I need to use Blend Surface to close the gap between the bottom surface and the bottle surface. When using the BlendSrf command, I can only pick 1 quadrant of the ellipsoid surface edge of the bottle surface. This results into a messy surface (see screenshot). I don’t understand what I am doing wrong. What should I do different?
I hope this is just a simple issue, much appreciated if one could help me out.
Hi Robert - you can get something if you use the ChainEdges option on the outer set of edges, but there is a problem with the bottle surfaces- they are not tangent at the seams:
Hi Robert,
The curves in the existing file that you are directed to open for this exercise are already rebuilt and do not require “refit rails” when doing the side surface with Sweep2.
Our bottle rail is a degree 3 curve with 34 control points. It was an ellipse at one time, however, it was rebuilt somewhere along the way.
If you are going to do this exercise with your own curves you can either:
Make the Ellipse with the Deformable option (12 control pts will work.)
Rebuild the Ellipse. We used these settings.
Or as Pascal suggestion “Refit rails” in the Sweep2 command
Any of these options will work if you are looking for a nice smooth bottle surface,
You can see the entire exercise here.
I will add a note to the next revision of the Level 1 with these recommendations.
**“If you are making your own curves…”, you will need to rebuild prior to the Sweep2 or “refit rails” in the Sweep2.
I think that the “Sweep 2 rails” tool should be upgraded to be able to properly use degree 1 input curves while maintain the simplicity of the geometry in situations similar to the bottle tutorial. This particular tutorial must be replaced with a better version, because the “Sweep 2 rails” fails to maintain the vertical nature of the profile curve on the top, no matter if the “Refit rails” option is on or off. The resulting unwanted deformation caused by the “Sweep 2 rails” tool may confuse the users who try to learn how to properly create industrial designs for manufacturing purposes.
I recommend to use the ! _RailRevolve command using the bottom ellipse as the rail curve and ignoring the top circle. Then, it’s a matter of a few simple adjustments of several surface control points to achieve the desired shape with perfect quality while maintaining the bare minimum of control points. This is the most efficient approach for this kind of objects. Here is a quick tutorial from start to finish:
I redid the exercise by creating my own ellipses and checking the ellipse curve provided by the exercise. Both versions are then pure ellipses, not rebuilt, and that works as well. So I am not sure if you need to change the exercise by asking to rebuild the ellipse if you use your own curves. Clicking the “Refit rails” command is necessary, and I agree that should be added to the exercise.
Could you please attached an unedited version of the Squeeze Bottle.3dm that you download from the tutorials panel?
I am accessing the Squeeze Bottle.3dm from the Tutorials panel, as well as the PDF.
When I open the the Squeeze Bottle.3dm, this is what I see: the top curve is an Ellipse and the bottle curve that is used in the Sweep2 is degree 3
Hi Bobi - using MatchSrf to the top circle and then SetSurfaceTangent may be a quicker way to get the clean bottle.
But I agree, this is perhaps not the very best context for using Sweep2.
In my opinion, tutorials like this one should teach new Rhino users how to check for potential deviations and make sure that the top surface edge is vertical across the entire length. The “Sweep 2 rails” tool generates a rather wrong result that makes two opposite sides of the surface on the top concave, as seen in my image example above. New Rhino users who are supposed to learn how to create objects from this particular tutorial may end up thinking that “Sweep 2 rails” is the proper tool for this kind of situations, eventually following the same mistake for their commercial or hobby projects.
The tutorial also didn’t mention that a simplified version of the overly-complex swept surface could be achieved by using the ! _RemoveMultiKnot command, at the expense of a minor deviation (control point count drops from 410 to 220).
The best way is add a second set of curves in the scene, next to the existing ones, so that the new Rhino users could try an alternative approach with “Rail revolve” and learn the pros and cons of each one of them. You can use my sample video as a base to teach the Rhino users how to achieve the best quality and lowest possible control point count (80 control points) in this tutorial.
Also, a 3rd set of curves may be added to teach the new Rhino users how to add a mirrored profile curve on the opposite end, as well as mirror-copy a profile curve at 90 degrees and then point edit the shape of the curve to adapt it to the ellipse, then make a new mirror copy to the opposite end and use “Sweep 2 rails” with 4 profile curves to create the bottle (it will produce a surface with 440 control points). This is a quite powerful way to adjust the shape subsequently while History recording is active.
I just did this for you here and also fixed the issue with the bottom ellipse: Squeeze Bottle 2022.3dm (824.0 KB)
Hi Pascal, some of the Rhino tutorials teach the new Rhino users how to get from point A to point B in the supposedly quickest way possible (the so-called “brute force”), however, this often leads to output geometry with an unnecessary amount of control points and generally difficult to edit subsequently. I think that the main focus of the tutorials should be to show appropriate techniques to achieve simple yet easy to edit geometry that consists the least amount of control points. The latter will let the users build extra details with a lesser possibility for errors, better surface quality, better viewport performance and a smaller file size.
Squeeze Bottle.3dm (124.9 KB)
Hi, please see here the 3dm model as downloaded from the Rhino tutorials webpage. This was contains a pure ellipse.
I now discovered the same models can be opened from the Rhino tutorial accessed from Rhino directly. Indeed that version contains a rebuilt ellipse. I will use these in the future, as I found out that not all curves mentioned in the exercise were in the 3dm file as downloaded. However, when I open the 3dm model from Rhino tutorial library directly, these are included.
Long story short: I probably used on old package of tutorial material downloaded from the Rhino archive.
