# How to make arc within extrusion path mesh

Hi Guys,

I have the following playground where I am creating vectors and extruding it to create the shape. How can i get the path between 2 vertices to curve? Is it the same as creating a curved line?

I’m not sure but I’d have thought you have to create multiple vertices to simulate a curve?

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One way

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@JohnK you are the best !!! I completely forgot about this doc page 2 Likes

Sorry, my math skills are less than stellar. I’m trying to draw 1/4 of a circle. Which type of curve would I need to do so? It would be much easier for me if there was a 3 point arc. Set the start, stop, and bulge

Given three non colinear vector3s this PG will draw the arc from first to third through the second. Steps determines the number of points

Just got it working - not properly tested.

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Thanks John. I don’t quite understand everything you wrote, I’ll have to research each command you’re using. But I get the concept of what you’re doing.

@JohnK Just checking that I understand this properly. So, a curve really is not a curve. It’s just a series or smaller lines positioned to resemble a curve. Is my thinking correct?

Correct, more steps the smaller the line segments.

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Here is a more tested version of the arcPoints function, there are bugs in the original.

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Now built in

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Awesome! So, if I want to do a quarter of a radius for example. Lets say I am adding a radius at the corner of a 90 degree intersection. Each intersecting line would be deducted the radius amount to establish the first and third points. Where would I place the second point? Should it be where the intersection would be between the 2 lines, or I need to do some math and find the point along the arc?

You would need to do the maths for the point on the arc. For the two lines meeting at 90 deg case deduct (1 - b) * radius from the point of intersection along each line, where b = sqrt(2) / 2.

Will do a more general case after the weekend.

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The following will join the end points of two lines in an arc tangential to the two lines for a limited set of lines.

The lines must be in the xy plane. The lines must be such that for each line traveling towards the end point the intersection of the lines must be after the end points and the lines point towards the intersection.

The following playground demonstrates this in more detail. The lines are generated to meet the above conditions. In practice the lines will be generated from user data.

The lines are given by end points f, yellow, and t, blue, (first and third of the arcFrom3Points) and the start points p, red, previous to f and n, green, next after t

The points f, t, p, n must be such that the grey intersection point will lie on the line p to f with the points in the order red, yellow, grey and on the line n to t in the order green, blue grey.

Right angles lines

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You Rock!

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