Custom Polyline GraphMapper. How?

Dear Grasshoppers.

I'd like to use a polyline as a GraphMapper curve, like this:

I would like to check the Y value of the polyline at regular X-intervals.

I could create a bunch of lines and intersect them with the polyline to get points, but is there a more "mathematical" way? Evaluate curve wouldn't work because then it wouldn't be even steps along the X-axes.

Any ideas?

Thanks!

Replies to This Discussion

Permalink Reply by taz on January 10, 2011 at 4:13pm

You could draw a curve on a reparameterized surface and use sliders to allow dynamic remapping of the domain.

Something a little more sophisticated than this:

http://www.grasshopper3d.com/forum/topics/apply-polylines-to-surfac...

Permalink Reply by Mårten Nettelbladt on January 10, 2011 at 4:40pm

Thanks Taz,

I'm afraid I don't really get it though.

The definition uses Divide Curve, but that will give me points that are spaced evenly along the curve (not along the x-axes).

And why does it need to be remapped to a surface?

Could you please help me understand?

Thanks!

Permalink Reply by taz on January 10, 2011 at 5:06pm

More like this...

You're right, you don't really need to remap to a surface, it's just handy to show something to draw on.

Attachments:

custGrph.ghx, 261 KB

Permalink Reply by June-Hao Hou on January 10, 2011 at 8:59pm

I try to mimic similar inputs for the Graph Mapper. Here is the Custom Graph Mapper:

Attachments:

custom graph mapper.3dm, 48 KB
custom graph mapper.ghx, 280 KB

Permalink Reply by June-Hao Hou on January 10, 2011 at 9:13pm

Here is a much simpler version by using a curve on a reparameterized surface, similar to what taz mentioned. You need to remap the number domains, though -- they are all in 0...1 now.

Attachments:

custom graph mapper 2.ghx, 103 KB
custom graph mapper.3dm, 48 KB

Permalink Reply by taz on January 11, 2011 at 12:04pm

Nice!

Permalink Reply by Mårten Nettelbladt on January 13, 2011 at 2:36pm

June-Hao Hou,

I've put your definition inside a User Object, for easy pull-down from the Componets Panel (User tab). I put your name in as "author". Thanks again! (UPDATED bug fix with domain remap).

Attachments:

Custom GraphMapper.ghuser, 25 KB

Permalink Reply by June-Hao Hou on April 14, 2012 at 2:58pm

Cool!

Permalink Reply by Georgios Anagnostopoulos on November 26, 2012 at 3:19am

cheers! very helpful

Permalink Reply by Mårten Nettelbladt on January 11, 2011 at 2:11pm

Thanks taz and June-Hao Hou!

All three versions seem to work just like I wanted.

Thank you very much for helping me with this one!

The only downside is that when I move the control points in the Rhino window, Grasshopper doesn't update until I release the mouse button. In GH GraphMappers the geometry updates momentarily.

Is there a way to make GH respond more directly or do I need to construct the polyline in GH?

Permalink Reply by taz on January 11, 2011 at 3:10pm

Er, that's one for the Mr. Rutten department...

You could move each point or vertex with an [MD Slider] (change the domain and input as a vector to [Move]) but that might be a bit tedious.

Permalink Reply by Mårten Nettelbladt on January 13, 2011 at 3:55pm

taz, I tried moving vertexes with MD-sliders here: