I have been experimenting ways to use Blender as a CAD program and I find Blender built-in PDT add-on to be best suited for me.

Following some tutorials i found on Youtube went well, and I start to try model something myself. The models turned out great, until I try to model this drawing: enter image description here

This model requires some tangent between two curves. However, I haven't been able to find any tutorials or guides online about this, so I tried to experiment it myself and trial and error through it, but it kept popping up a message saying that I have to work in Vertex mode (which I am):

enter image description here

or this message, which says the distance between the points were too close:
enter image description here

I tried to fix the problem, but once I correct the error, the other message appears.

Does anyone know how to fix this?


1 Answer 1


I would create those two tangents like this:

First I open the PDT Tangents menu. I have set the Tangent Mode to Outer and selected the first circle. Then I click on the Set From Arc button under Centre 1. As you can see, this sets the XYZ values of the circle center and the radius to 0.66 m:

select first arc

Then I select the arc to the right (only the vertices that belong to the arc itself) and click on Set From Arc under Centre 2 this time, it sets the XYZ values of the arc's center and a radius of 1.5 m:

select second arc

If I now click on the button Tangents From Inputs, two edges are generated. One tangent from the upper part of the circle to the top of the arc, another one from the lower part of the circle to where the lower part of the arc would have been (of course I only need the upper tangent and delete the lower):

tangents from inputs

To get the tangent from the corner vertex on the left to the circle, I switch the Tangent Mode to From Point, select the corner vertex and click on from Vertex under Tangent Point. This sets the XYZ coordinates of the corner vertex:

select corner vertex

Then I select the circle and click on Tangents from Selection:

tangents from selection

This results in two tangents, one upper from the circle to the corner and a lower one as well. Other than the two separate ones earlier, these are two connected edges sharing a vertex where the corner is:

connected tangents

After selecting the lower edge and deleting it, the only thing left to do is a little cleanup and connecting the tangents with the arcs, because they are not always exactly hitting the edges/vertices of the arcs (I guess because mesh circles are only approximations to a real circle, limited by their amount of segments).



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