Pick up grasshopper point in rhino?

Replies to This Discussion

Permalink Reply by David Rutten on April 16, 2011 at 3:45am

Hi YJ,

 

you cannot pick Grasshopper points in Rhino. They don't exist as far as Rhino is concerned.

 

What you can do is reference an existing Rhino point object. When you go to specify a point in the Point Parameter dropdown menu (Set One Points or Set Multiple Points) there's a Type property. Change this into Type=Point and you can select Rhino points. Whenever you drag these Rhino points about, it will update the Grasshopper solution.

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Adriana on June 14, 2012 at 8:23am

I'm also having trouble referencing geometry from Rhino.  I'm completely new to both Grasshoppper and Rhino, and I feel like I'm missing something very obvious.

When I right click on a parameter I don't see the Type property.  It seems like I can only reference pre-drawn Rhino geometry for some parameters.  For example, when I set curves and points, I can pick existing ones in the Rhino window, but when I set rectangles and circles, I need to draw new ones.  How do I access the Type property or select existing Rhino geometry to set a parameter?

Permalink Reply by Danny Boyes on June 14, 2012 at 8:43am

Hi Adriana,

After selecting "Set One Point" for example you should see in the Rhino Command line (Type = Point)

This behaviour changes. If there is no point in the Rhino Document then you will have co-ordinate by default but once you click "type" you can set it to Coordinate, Point or Curve (which is a point on a curve)

Permalink Reply by David Rutten on June 14, 2012 at 8:48am

Hi Adriana,

hopefully without getting too technical, here's how the interaction between Grasshopper parameters and Rhino geometry works.

Certain parameters in Grasshopper can reference Rhino objects. Point, Curve, Surface, Brep, Mesh, Box and the generic Geometry parameter. This means that you can have an actual object in a 3dm file that can be associated with a Parameter. When the object changes, Grasshopper will respond to this and update as well.

Other parameter do not support this feature. Line, Circle, Arc, Vector and Plane for example do not. You cannot reference a Plane or a Vector because Rhino doesn't really have these kinds of objects. You cannot reference lines, circles and arcs because they are not guaranteed to stay lines, circles and arcs. You can scale1D a circle for example and turn it into an ellipse. The Circle parameter in Grasshopper cannot store ellipses, so it would result in a weird error. This is why all curves must be imported using the Curve parameter, even when those curves are lines, rectangles, circles or arcs.

Points are special though because they are a bit more complex. A Point parameter in Rhino can store 3 kinds of different points. A point can be just a single coordinate (x,y,z), it can be a referenced point object and it can be a point on a curve. So when you go to set one point via the Parameter menu:

you'll get some extra options in the Rhino command line. It will look something like this by default:

and when you click on the 'Type=Point' text, you'll get all 3 options:

Depending on which one you pick, you can either select a Rhino point, or click anywhere in the Rhino viewport or click somewhere on a Rhino curve.

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Adriana on June 14, 2012 at 10:10am

Ok, I understand now.  Thanks, David and Danny, for taking the time to answer my question!

Permalink Reply by YJ on April 16, 2011 at 7:06am

Thanks, David,

Could I have a chance to know how this is possible?

http://www.grasshopper3d.com/video/interactive-optimizations

Permalink Reply by David Rutten on April 16, 2011 at 7:52am

You'd have to ask Daniel how it's done, but I don't see anything out of the ordinary here. He probably referenced some Rhino point objects, then used those to control Kangaroo inputs.

 

He's doing it in Rhino5 since he's got the gumball modifiers.

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by YJ on April 16, 2011 at 2:56pm

Oh, sorry, I thought he was picking the point on mesh while it is deforming, but I just realised it is pre-refered at beginning as restrained points.