Is there any way?

I want to convert the straight line (No.1) into the the curve (No.2) that are matched accurately but with different length (No.3 - just the same length of the straight line)). Is there any command in Rhino for this purpose?

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No single command.

What do you mean by “matched accurately”?
Is No. 3 a scaled version of No. 2?
Is No. 3 a shortened or extended version of No. 2?
Something else?

For example, I want to sketch a car body:

The blue line is a single straight line. I want it takes the shape of the red curve without any distortion or deformation.
In some situation the distances of two points of the blue line may is a little different with the distance of the start and end points of the red curve.

Is there a command that can form (convert) the line similar to the the red curve, in its place ( so that the blue line follows the red curve precisely)?

line 2

Copy the red curve to the position of the blue line, with one end coinciding.
ScaleNU the copy of the red curve so that the other end of the copy coincides with the other end of the blue line.

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Strictly speaking these two requirements are logically incompatible. There has to be some adjustment.

What’s missing here is a statement of what adjustment is acceptable. For example, if the blue distance is greater than the red distance, do you stretch the new line or do you extend one end or the other or both? If a vector from start to end of the blue line is different from a vector from start to end of the red line, do you rotate the new line or shear it? Which end is anchored? If the blue distance is shorter, do you scale the new line, or truncate it? If truncating, at which end or at both? After adjusting the line, do you need to match the ends to the adjoining curves to achieve some degree of continuity, thereby changing the curve further from the shape of the red one?

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I think that your design intent here may be in trouble at least by the curvature and direction of the RED highlighted curves.

Furthermore, the two CYAN highlighted curves are doing a lot of work here, and at first glance appear to be contradicting eachother somewhat. I would imagine that these are two elements in your design with a lot of power over the surfaces, and will likely dictate the extent to which you can realistically scale your DARK BLUE curve to match that of your red curve.

As soon as you MatchSrf any surfaces (assuming you want quad patch here, constructed using the curves), then it will likely drop a lot of the conformity to your underlying dark blue curve anyway, especially as the curvatures will fight.

image

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Thank you so much for the solutions you offered. They can be used in different situations, though I think the Rhino developers can create such a new command to shape a line according to the shape of a curve fundamentally, like this example.

Although offset can be used with some manipulation, nevertheless I think there is a need for such a new command in Rhino.
For instance, simulating these two curves with different scales.

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Here, senior David Cockey’s solution was more useful to me in this case.

Thank you :slight_smile: