# How to connect a tilted circle to a tilted ellipse so it creates a nice smooth conical section

The attached .skp file shows a tilted circle on top and a tilted ellipse below. I would like to connect the two to form a smooth conical section. However, I don’t think this can be done using the extruder as this would produce a different ellipse than the one shown. Also, I have drawn two lines; one at each of the ends furthest from the center of the ellipse (along the major axis) and the center of the circle. These lines indicate what the cross section of the ultimate shape will look like. I don’t think connecting along the long line should be a problem but connecting along the short line in the back of each shape might be, but I would like to have that happen if possible. My ultimate goal is to get the volume of the produced conical shape connecting the circle and the ellipse.

P.S. As a beginner, I’ve done my best to “line up” the shapes. I’ve looked at them from many perspectives and they look “lined up” to me (i.e. one on top of the other)

Transition Zone - 45 deg.skp (219.0 KB)

If I’m understanding correctly , then there are a few ways

Draw a solid cylinder, Then select only only the top face/edges and rotate , scale and move it into position.

Or

Use an extension such as curviloft to join your 2 circles with sides

Or simply draw lines from one to the other to create the faces

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When you say draw lines, do you mean draw say 24 lines (since that is the default for the circle) and connect them from circle to ellipse. If I do that, how do I create a face? I assume that the faces would be created between adjacent lines.

That’s right, draw the 24 lines - faces will be created if they are coplanar.

If they are not created : then draw an additional diagonal line to create a triangular face.

Once you got all of the faces drawn, use the soften/smooth slider on the whole model to smooth out any unwanted visible lines.

This illustrates what @DaveR explains in the screenshots above.

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I tried a different approach, that uses push pull, move, and rotate. For my case I made the numbers slightly easier than yours, with circle diameters of 2m for the smaller one, and 3m for the bigger one.

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The way I did it was basically what you said.

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Colin: How did you get the shape to remain in cross section even after orbiting around? I didn’t do that and SU wouldn’t give me a volume, probably because wrong points for connection were selected. Your method would be good for me because I have to make this diagram for at least six different angles of the original circle.

Do I have to draw lines across the face of the circle as well as shown in Royce’s drawing below. I created all the surfaces between the circle and the ellipse, but SU still won’t provide a volume measurement.

No need for stitching across the top and bottom single plane surfaces. Did you make it a component? Sketchup gives volumes for solid components, not raw geometry. Select all the geometry and make it a component.

Yes. I did make it a component. The surfaces between the ellipse and circle look okay, but some of the lines are funny. I’ve attached an updated file. BTW: How does one delete a component in free SU? I go to the right side and select components, but it won’t allow me to delete them. I have to instead “Undo” until I get to the point where the component was created.
TransitionZone - 45 deg - Alt.skp (247.4 KB)

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If by “delete” a component you mean erase it from your model, then select it and press delete. If you mean release the geometry from being a component then right click and choose explode, but this is almost never necessary. Instead to edit geometry in the component just double click on the component to open it for editing, change whatever you need and then click once outside the bounds of the component to close the component editing. Or right click and choose edit component.

You are not seeing a volume because your component is not a solid, it’s not a solid because it contains one stray or “extra” edge at the small side of the side surface. Erase that edge and you’re good to go.

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Yes, that was the problem. Now I am able to get a volume. One other question. If I want to smooth the edges, it looks like I have to select each of the surfaces between the lines separately. The Soften/Smooth Edges doesn’t work if the component is selected as a whole. Is there a workaround to do them all at once. As I said earlier, I have to create this diagram for a number of differently inclined circles and ellipses and using this surfaces technique already involves a lot clicking. Thanks.

It should work on the whole component (or maybe it works on just groups)

In any case, select alll of the geometry inside of the component, tick both options in the smooth/soften and adjust the bar until it is somewhere between 20-30degrees (or it looks right)

Similar to previous advice, open the component for editing first. Think of components like containers, let’s say ziplock bags. You take a handful of candy (geometry) and put it in a bag so it stays organized and you can move it as a unit. If you need to add or subtract or work with the candy you have to open the bag. So in this case, double click on the component to get inside the container and select all the geometry with a selection box or by triple clicking on any part of it. Then perform the soften smooth operation, then close the bag (component).

That did it guys and I should have known that I needed to first edit the component. My next task is to see if I can take this drawing and change the angle of the circle and the angle of the ellipse and length of the major axis of the ellipse without losing the surface connections. If I can do that, then I should be able to readily create the other drawings I need.

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Open the Component, select only the surface to rotate, invoke the rotation tool, click once to place a fulcrum (use the arrow keys to lock an inference direction), click a second time to grab the surface for rotation, start a rotation then let go of the mouse and type in degrees and press return.

The circle and the ellipse are broken up into 24 sections each. I’m try to select just these items using a window drag technique but it always wants to select more. So, I selected each section as well as the face by holding down the shift key and then grouped them to recreate the original circle. But now when I rotate the newly created circle the the white sides don’t move with it. I think this may be too complicated for me. I’m probably just going to have to recreate for each different tilt.

I am using your file in my example. Your top surface is broken into hidden sections unnecessarily but it can be selected as a unit. You can also erase all those lines as they do nothing for your model.

What you posted was an image and not a gif correct? I can’t tell what you did. But thanks for your help and everyone else who responded. I’m going to do it the brute force way, because I also need to adjust the distance in the vertical direction to specific measurements that I get from Geogebra. Thanks again.

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