CLARIFICATION OF JOIN IN GH

Can somebody give me a clarification on what join components do in GH?Are they similar to grouping?

Are they used on surfaces and meshes to eliminate naked edges?

Does anybody have an example for their use?

Thanx a bunch

Replies to This Discussion

Permalink Reply by David Rutten on March 26, 2013 at 2:47am

Join in Grasshopper is pretty much the same as Join in Rhino. When you join a collection of curves then the ones that are touching at their ends will be merged into a single curve. When you join surfaces then the ones who have edges in the same places will be merged into a polysurface. Joining meshes simply puts all the meshes into a single new mesh. A joined mesh does not need to be a single shape, it can consists of multiple disjoint pieces. This is not true of curves and surfaces. Join is typically undoable by an Explode operation, though again meshes are special.

There are other operations somewhat in the same class as joining that nevertheless do different things. Welding for example is an operation performed on a single mesh. If two mesh edges are in exactly the same spot (they are said to be coincident) they will be merged into a single edge. So where before you had 4 vertices (one at each end of both edges) there are now only 2 vertices left, because there is only one edge left. The properties of these 4 vertices (colours, texture coordinates, normal vectors) will be combined as well. Welding is not a fully undoable operation except in a few special cases.

Merging coplanar faces combines two adjacent surfaces that are part of a polysurface into a single surface. For this to work both surfaces need to be flat (planar) and have the same orientation (co-planar). Again, this is not a fully undoable operation except in a few special cases.

Grasshopper does have Groups as well, but they are different from Rhino Groups. Grasshopper groups are basically just aggregations of geometry which makes it somewhat easier to transform them all in one go. Groups in Rhino are all about selection states and Grasshopper doesn't have a notion of 'selected objects'.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by pantelis apostolou on March 26, 2013 at 1:22pm