Re-Proportioning a Cone


#1

I have an existing image of a cone (see attached graphic.)

I would like to make the base wider, so it is not a tall thin cone, but instead is a thick cone. Is there a way to do this without re-creating the image from scratch?


#2

Is it an image or is it a SketchUp model? If it is the latter, just select the base of the cone and use the Scale tool to change its size.


#3

Alternatively, select the entire cone and scale it down along the Blue (vertical) axis.

-Gully


#4

This is a good opportunity to exercise the power of the Cardinal Points.


Skew function like old 3D Studio?
#5

We all love those Cardinal Points.

I was blown away when I first found out.


#6

I remember … and I think that SketchUp is a good tool to use to easily convey (at lest on your part) these geometric intersections:

2015-11-10 07h05_29.mp4 (1.6 MB)


#7

Thanks for all your advice. I did not realize there were so many ways to do it.

I have started my next graphic, showing a cutting plane going through a cone to create a parabolic section (see attached.)

Two more questions and then I think I’ll be able to complete the image.

Is there a way to ensure that the cutting plane is parallel to one of the sides? Presently, the cutting plane in the attached image was made by eyeballing it, but I’d like to be more accurate if possible.

Is there a way to include hash marks on the cutting plane and the edge of the cone to indicate that the cutting plane and edge of cone are, indeed, parallel?

Many thanks for all your help.

Uploading…


#8

I think that the simplest way is to construct a triangle with known angles and use that to generate the cone. Then you can rotate the section plane at the same angle. For example, using a 30-60-90 triangle*:

2015-11-11 18h32_03.mp4 (831.2 KB)

*(Tried to upload an animated GIF, but it says I exceeded the 5KB limit)

I’m not sure what you mean about the hash marks … usually I see something like:

Can you include an example of what you mean?


#9

It is easy enough to construct a plane at the same slope as the side of a cone of any angle using guidelines.
Screenshot - 11_11_2015 , 8_02_11 PM

And then, after intersecting the plane with the cone, pull out the parabola
Screenshot - 11_11_2015 , 8_05_10 PM

As for making the tick marks, you can certainly do that by drawing them or adding a label and use // to indicate parallelism.


#10

Another option, you can use the facets of the cone to align a Section Plane and use that to create your edge. Here I have rotated the original circle so the flat of the facet is on axis rather than the vertex. This way you can use Camera/Standard views/Front.


#11

Not trying to be picky, but the angle of the facet is not the same as the angle of the edges of the cone. Visually, it doesn’t make much of a difference, but mathematically, it yields a different result.


#12

No doubt you are correct, when buying drinks for myself and 2 friends my mathematical abilities only allow me to order 2 gin tonics and another gin tonic.


#13

Hi folks.

Constructing a cone from a cylinder is not accurate since the result is a cone frustum with one very small flat face. A real cone has only one flat face. The opposite end is a point.

It is easy and quick to build a cone from a triangle lathed around a circle using the “Follow me” Tool.

Just ideas.

Jean


#14

Or by drawing a couple of diagonals to a circle and lifting up the center point with Autofold enabled.

Anssi


#15

Once again, thanks for all the advice.
Up to now, I have been learning SketchUp by watching YouTube videos. You have given me a lot to think about: “using guidelines”, “pull out the parabola”, “Follow me tool”, diagonals with Autofold enabled", etc. Mind blown! I will have to spend some time exploring these techniques.