Grasshopper point MD slider and point on surface don't correspond

Grasshopper
1

Hallo everyone,

Added a simple part of a paramatric model that does not respond as I would expect.
The point on the surface doesn’t follow the point of the MD slider.
What am I doing wrong?

Regards,
Dirk

example.3dm (38.0 KB)
example.gh (6.7 KB)

2

You are getting a warning from the Fit Loft component because you’re only supplying 2 curves. You can eliminate the warning by supplying more curves or using the Loft component.

fit_loft_001
fit_loft_0012464×972 199 KB

The v-direction of your surface is oriented to the negative Y-axis. You can change this by reversing the order of your curves (right-click on the Curves (C) input to the Fit Loft component and select Reverse).

fit_loft_002
fit_loft_0022464×972 200 KB

If you want the output from the Evaluate Surface component to be at the center of your surface when the MD Slider is set to 0.5, 0.5 you can reparamaterize the surface (right click on the Surface (S) input to the Evaluate Surface component and select Reparameterize).

fit_loft_003
fit_loft_0032464×972 201 KB

Alternatively, you could adjust the parameters of the MD Slider by double clicking it and setting it’s X-Domain to 0 to 10 to match the parameters of the surface.

fit_loft_004
fit_loft_0042228×1048 204 KB

-Kevin

3

Assigned to Grasshopper category

4

Hallo Kevin,

Thanks for your answer.
I used the other loft command and reversed it, but still the x and y direction get swapped.
When you look at the x and y positions in the MD slider, they are correct, x from 0 - 1000, y from 0 - 2000.
But when you move the point in the MD slider and look at the point coordinates of the EvalSurf, you’ll see that the two have been swapped.
This is a test in the flat plane, but after this it has to be put in 3D, so I want to understand what’s happening.
Hope you can put some more light on it.

Dirk

example.3dm (39 KB)

example.gh (8 KB)

5

You can transpose surface parameterization (swap U and V) with a plug-in or script.

Here I’ve done it with a one line C# script.
example_re.gh (14.1 KB)
(references your Rhino file)

-Kevin

6

Hallo Kevin,

It works. Thanks a lot.
I thought that I was doing things wrong, but as I understand, Grasshopper itself does not have the possibility to do this, and actionally it is some kind of bug.
Is that correct?

Regards,

Dirk

7

Rhino 8 has a Transpose Surface and Reverse Surface components which would I think do what you’re looking for.

8

Hallo Andy,

Thanks.
Have ordered Rhino 8 last week.
Have to install it next week, and will try your suggestions.

Dirk

9

I have Rhino V8, but am still using V7 most of the time.

I tried the Transpose Surface component in Rhino 8 and it does the same thing as the one line script in the file attached to my previous post.

-Kevin

1 Like
10

Hallo Kevin,

Thanks a lot. It works, not just in the flat plane, but also 3 dimensional.
This was the part where I got stuck last year.
Added a short video that shows the result.

Kind regards,

Dirk
IMG_9792.MOV