Closest distance from a point on a curve to the start or end of the curve

[Browning_Zed]

Hi all,

I am trying to find a solution how to get the distance along a curve from a specified point lying on the curve. I specify a point in this way:

(setq
    curveobj (entsel)
    closepnt (vlax-curve-getclosestpointto (car curveobj) (cadr curveobj))
)

Now I need the following steps:
1. Find out the distance from closepnt to the start of the curve;
2. Find out the distance from closepnt to the end of the curve;
3. Compare these two distances, and if distance 1 is less than distance 2 then return T, otherwise nil.

Thanks in advance for your help.

`

[ВeekeeCZ · Accepted solution]

1) use (vlax-curve-getDistAtPoint curve-obj point)

2) use (vlax-curve-getEndParam curve-obj) and (vlax-curve-getDistAtParam curve-obj param) and dist from 1)

3) use '< func and distances from 1) a 2)

[Browning_Zed]

Thanks man, you're great as always. I did it thanks to you.

(setq
    enselobj (entsel)
    curveobj (car enselobj)
    startdis
        (vlax-curve-getDistAtPoint
            curveobj
            (vlax-curve-getclosestpointto curveobj (cadr enselobj))
        )
)
( < startdis
    ( - (vlax-curve-getDistAtParam
            curveobj
            (vlax-curve-getEndParam curveobj)
        )
        startdis
    )
)