Surface curvature analysis, like "zebra" in Rhino

Hi there,

does anybody know of a way to generate the zebra stripes pattern in grasshopper that is available in Rhino (Analyze - Surface - Zebra)?

I searched RhinoCommon, but that didn not help me very much. I found "VisualAnalysisMode Class", but I could not figure out how to use it...

What I would like to do is:

- I have a brep in grasshopper (with multiple faces)
- I would like to display this with zerbra stripes as Rhino does it to visualize the surface curvature

Any ideas?

Best regards
Stefan

Replies to This Discussion

Permalink Reply by David Rutten on July 24, 2013 at 2:37am

The zebra stripes depend on camera position as well as shape. I do not know how to mimic it though.

Would using a regular reflection environment map be enough for your purposes?

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by Stefan on July 24, 2013 at 3:55am

I tried this in Rhino (Analyse - Surface - Environmet Map) using an image with regular stripes and that looks promising.

I'll be grateful for hints how to realise this in grasshopper!

Thanks in advance
Stefan

Permalink Reply by David Rutten on July 24, 2013 at 10:55am

I attached a rather nasty VB-component hack. It works, but probably isn't very fast.

David Rutten

david@mcneel.com

Tirol, Austria

Attachments:

zebra.gh, 9 KB
stripes.png, 1 KB

Permalink Reply by Stefan on July 29, 2013 at 11:25pm

Excellent! That's it.

Thanks a lot.

Best regards
Stefan

Permalink Reply by rob(E) on August 14, 2013 at 10:54am

So based on the "environment map" idea.....how could one achieve this with projected curves? Is there any sort of "reflection" or environment project teachniques to map curves onto the surface using the same logic? Thanks!

Permalink Reply by panhao on August 14, 2013 at 10:19pm

Millipede has a component to draw lines on mesh.The input param is a numeric value for every vertex of the mesh. You can Convert the zebra meterial to a Domain and iso value for the mesh.

Permalink Reply by David Rutten on August 15, 2013 at 2:16am

How would you convert a reflected UV coordinate into a mesh vertex though?

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by panhao on August 15, 2013 at 6:21am

for example if the whole map represents domain 0 to 100 and 0-20 40-60 80-100 represent black. Of course 20-40 60-80 is white. then the iso values are {0 ,20 ,40 ,60 ,80,100} .

Each MeshVertex get a data related to the viewsite and then map these data to 0-100.The data can be distance, the vector angle between the priciple curvature and view or something else.

Permalink Reply by David Rutten on August 15, 2013 at 12:03pm

My point was that the reflection map does all sorts of nasty things (topologically) to the environment map. Although the Zebra map is just black and white stripes, in the reflection we find little isolated islands of black within white and vice versa.

I suppose you could try and tackle this on a per-triangle basis, but it still sounds pretty tricky.

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by Saya Ye on October 7, 2013 at 4:35pm

Based on reflection map, how to make the pattern as a regular texture? Thanks!

Permalink Reply by David Rutten on October 7, 2013 at 4:41pm

This is a script which puts colours on a mesh instead of a texture. It doesn't handle parallel views too well at the moment, but that should be an easy fix.

David Rutten

david@mcneel.com

Tirol, Austria

Attachments: