I posted a thread a few months back (Numerically editing objects) looking for some help wrapping my mind around the basics of modeling in Rhino. While the replies were great and helpful, I still found myself bumping up against a lot of frustrating problems and eventually put this part of my project aside out of frustration.
Unfortunately, I’m now at the point where I can’t put this off any longer, and I’m hoping someone will hold my hand and walk me through a few of the problems I’m having.
I’ll start off with an angled cylinder, like last time:
I’ve realized after I’ve already created and rotated the cylinder that the diameter is wrong. Presumably, I would select the cylinder, use Scale2D, select the cylinder vertex as the origin point, then select another reference point before entering my scale value.
Unfortunately, I cannot figure out what the reference point should be. Selecting the midpoint on the end of the cylinder gives the wrong result:
Am I going about this all wrong? Or is there just a specific Osnap combination that will give me the selections needed to scale the cylinder’s diameter without setting the whole thing askew?
Thanks so much in advance. I feel like such a moron right now
Hi Carl - a key to this is that Rhino works off of the current construction plane in many operations - your Scale2d needs to be run with a Cplane centered on the end of the cylinder. To do this, start the CPlane command, and if the cylinder is capped, choose the Object option and click on the end cap of the cylinder - then Scale2d with the base of the scale set to 0 (current CPlane origin). To reset the CPlane to how it was, use CPLane >Previous.
Sometimes it is easier to just scale 3D and then fix the third dimension. In this case, snap to the center of one end of the cylinder and Scale3D the appropriate percentage, using the copy option. Then Scale1D the copy to bring the length back to that of the original.
In other cases, it may be faster and more intuitive to do two Scale1D commands than one Scale2D. For instance, you could Scale1D with the center of one end of your cylinder as the origin, the edge of that end as the first reference, and then enter a new radius. Then flip to the top viewport and repeat the operation perpendicular the the first scale. Uses the world C planes, and does not require capped ends.
Nothing wrong with Pascal’s approach, I just find it easier to visualize what I’m doing using world C-planes (read, I’m less likely to make a mistake). But please, take the time to learn how to set custom C planes (and return back to world planes), as there are lots of other uses for them in addition to this one.
The next problem I’m running into is probably more of a general issue with not understanding NURBS modeling, so I apologize if I’m asking questions that are way too general for the scope of this community. (I certainly understand if you don’t want this forum to devolve into a “teach me 3d modeling concepts” discussions, and I’ll withdraw my questions if they’re deemed problematic.)
I need to “ovalize” one of the ends of my cylinder before mitering it to another cylinder.
When working with polygons in another application, I’d start with a lowpoly object and cut a loop where I want the ovalization to begin:
How do I go about doing this same sort of thing in Rhino? I’m assuming there’s a way to add additional “loops” along the cylinder object, then manipulate the ends independently of the rest of the cylinder, but I’ve spent a couple of hours trying to figure it out and haven’t made much progress.
Make a new cylinder on top of the original one and with the same diameter. Then subobject-select [Ctrl+Shift+LMB] the top edge only of the new cylinder. Scale1D that one edge only.
For smoothing out the two cylinders, you will have to fillet / blend the shapes. Or extract the edges and loft…
I want these two cylinders to be aligned so the end of the vertical one meets the exact center of the horizontal one. I cannot, for the life of me, find a combination of Osnaps to let me do this. The closest I can get is turning on vertex snapping, which gives me the right position vertically, but screws up my position on the X axis:
Maybe it’s all in what you did before you made the move, i.e.: how you made the two cylinders. That will have a lot to do with what is available for snapping and snapping to. It’s hard to tell for sure without the actual model (3dm file). Does your model have actual centerlines for the cylinder in it?
Create a line that runs through the centre of the cylinder using the centre snap and the cylinder ends. Then group the line with the cylinder and snap to the lines middle and end to orient. Ungroup and delete the lines when you are done.
Set the Cen Osnap. Select the smaller cylinder, start Move.
At the prompt for the point to move from, start the Between one-shot Osnap (type Between, or Ctrl-key hover over the Osnap toolbar to see the one-shots and click it there).
Now, to set the Between points, snap to the centers of the ends of the small cylinder.
As the to point, snap to the Cen of the longer cylinder.
@Willem Hmm, that sounds like what I was looking for based on your description, but I can’t actually get it to work. When I have “Project” checked, the vertex snapping stops working.
@pascal Yes, that’s it! I had to kinda reverse the process because I wanted the lower cylinder to stay where it was, but this was exactly what I needed. Thank you!
