# How to make a curve when having a corner?

Let's say a table or something that is made from a cube. I have the corners of the table and I want to make them more circular. How is this made?

I know bevel technique that can make it a bit more smooth, as I did here, but I want it totally circular.

• What application? Commented Sep 18, 2018 at 13:33
• Why not just increase the bevel radius until it's completely round? Commented Sep 18, 2018 at 13:54
• @joojaa It's in Cinema4d like the tag the question has. Commented Sep 18, 2018 at 14:44
• @PichiWuana yes but you need to have that info in body text too, otherwise we dont know what restrictions your question has. Commented Sep 18, 2018 at 15:13
• Howabout draw the shape with splines and extrude Commented Sep 18, 2018 at 15:14

## 2 Answers

I haven't 3D software for artistic modelling, but elementary methods in a freeware CAD program maybe are applicable also for your purposes. See a screenshot:

In the left there's a sketch drawing, only straight lines on the working plane

In the middle two concentric circles have been added. I have snap to grid ON, so there's no problem to make them concentric and tangential with the line sketch

In the right all unwanted line and curve segments are deleted (=trimmed away) one by one with the eraser.

The next step is to pull some thickness:

The sharp edges can be rounded directly, but as well one can sketch a rounding profile (no need to make it circle, other curves are ok)

Again remove the unwanted arc segment. Then select the sharp corner areas and extrude (=sweep) them along the edge:

After completing the sweep there actually are 3 solid pieces in the same space:

It's fortunately possible to subtract the sweeped solids from the original body. The result = the rounded piece:

As mentioned, sharp edges can be also rounded directly. That obviously is what you called Bevelling:

If the rectangular piece already happens to have the thickness and it doesn't fit to any grid, the case is more difficult:

Fortunately even simplest CAD software have a snapping mode where tangential circles can be drawn. Here a diagonal line has been draw at first through the corners. Its end is the common centerpoint of the circles.

The areas between the circles and the original body can be extruded in CAD programs both to remove and insert the material. Here's a piece is removed by extruding:

After making the rest of the needed extrusions and removing the unwanted splinters, we have the solid arch:

BTW: Direct rounding works in this CAD program also with sharp corners:

The used program = DesignSpark Mechanical, it's a heavily disabled version of SpaceClaim Engineer, but still a valuable tool.

• This is a wonderful general 3D answer, and I'm thrilled with the level of response you gave! I was trying to stick with the OP's C4D origination of the question, hence the specific spline to extrude and cap bevel answer based on the C4D workflows... but I far prefer the conceptual and design level of your response - fits how I model in both CAD apps and general 3D tools like modo; I also think your answer will be of greater transferrable use to other questioners over time - brava! Commented Sep 19, 2018 at 17:29

@Pichi Wuana, I'm not sure which direction you're asking for a curve in, but just in case... I made a spline extrude to get a curve at the inner corner, and did a filleted cap on the upper cap to get a smoothly curved edge at the counter's upper edge... looks like this:

As you can see, you can control the number of steps in the fillet curve with the step count to make it smoother or less so, and the radius with the Radius size, so it's easy to get a circular edge bevel if that's what you mean - and the curved inner corner (in plan) of the counter is just how I drew the spline I then extruded.

To get a circular cross section at the counter's edge, you would set both start and end caps to fillet cap, set a high step count (<6) and in both, set the radius to exactly half the depth of your extrude.

Hope this helps.