Draft Angle Analysis Component

Here’s a sample definition that allows you to perform draft angle analysis on meshes from inside Grasshopper. Should work in Rhino 6 and Rhino 7 on Windows (not Mac yet, sorry)
https://github.com/mcneel/ghgl/raw/master/src/tests/draftangle.gh

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Dear Steve,
thank you so much. No need to go over bake/Rhino anymore (several times daily)!
Now one more little wish. It is really just a tiny step:
Please give a variable angle range (eg 0-1 Deg) white and the following range black color (here then 1-2 Deg) aso. Call the component isophotes analysis. Then we will have finally at true isophote highlight analysis from a fixed direction. Please also include this into Rhino itself to replace or complement the horrible Zebra light, which changes on geometry from every viewpoint. This will make a more professional touch. This isophote function is a longtime basic analysis in ICEMsurf, probably in Alias too. Its was also part of the VSR-Tools under Rhino5.
Best regards, Norbert.

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Is this getting close? isophote.gh (541.7 KB)

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Thank you very much.

You are definitely close to it. First condition is fulfilled: The pattern is not dependent on the view anymore but on a vector or plane. Excellent!

I am not sure if these are real isophotes. The screenshot shows a ball (left in isophote.gh, right in VSR-Tools). I will get back to you with a further analysis, but earliest sunday.

The further analysis on a sphere leads to the following conclusion: e.G. VSR-Tools divide the black/white stripes according to equally spaced section cuts normal to light direction. This is only valid to the sphere. Irregular shapes are not divided by section cuts but by isophote lines. I was not able to figure out what mathematical method was used to define the width of the black and white areas. It is not equally spaced angular ranges (e.g. 0-1 deg white, 1-2 deg black aso).

@Steve Baer This works really good. Could this be added to Rhino 7 as an (additional) Zebra-Analysis?

Zebra stripes that are NOT view-dependent but constant to vector, are essential for surface evaluation, as they do not change while rotating and working on your surfaces.

Best regards!

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Hi -

I’ve now made sure that it’s on the list (RH-58682) but it’s unlikely that it will be in Rhino 7.0.
-wim

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Great! Thank you very much Wim. This is a huge help for us surface modelers.

thanks for the Draft Angle Analysis.

is it possible to deduce color or points. only from the red zone ???

avto SPURE.gh (47.6 KB)

I do not understand this question.

возможно ли это сделать ?. получить точки. только в красной зоне. ?
is it possible to do this? get points. only in the red zone. ?

This component is only for visualization. It does not output any geometry in Grasshopper

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thanks for the answer
it is a pity that there is no possibility.

Is the part of the Rhino draft angle analysis command that outputs draft curves something that could be ported to Grasshopper?

For fabricators, those curves are as important as the visualization, if not more. And these curves are ultimately what the previous poster would need in order to derive points only in one draft zone.

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I added this to or wishlist at
https://mcneel.myjetbrains.com/youtrack/issue/RH-61690

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Thanks!

I’ve modified Steve’s original example to include silhouettes based on the provided angles using a scripting component. This should work as a stop gap until the component is made.

draftangle with curves.gh (15.5 KB)

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thanks.!!! :+1: :fist:
but how to get lines on the mesh in small areas?

extracting the curves on the mesh is going to produce several fragments. I would suggest using the brep and tuning your values accordingly.

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when resizing the mesh I can get the ones I need. points.
but I would like to be in another zone.