"Random" problems

1. We've just updated to 0.9 and certain things have changed. What I'm trying to do is generate a grid of points on a surface and them move (copy) them with a random height. They only randomize in rows, but not as individual points. Why is that and how can I fix that?

2. Also, I'm trying to do this tutorial: http://digitaltoolbox.info/grasshopper-basic/data-matching/ But I'm not able to "cross reference" anymore (@ 2:40minutes in the video) I know they have a new cross reference button, but it does not work the same way. It cross references all points with all other points all across the board. it's sort of crazy looking. How can I fix that?

Thank you!!

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Permalink Reply by David Rutten on October 22, 2012 at 2:37pm

If you updated from way (waaay) back, then the new behaviour is probably due to the datatree output of Surface Grids. A long time ago in a galaxy far away all the points in a grid were stored in a single list. This was a bad idea as it becomes very difficult afterwards to find neighbouring points in both directions. These days points in a grid are stored in separate columns, and the columns are stored in a datatree.

You can either choose to destroy this nesting structure and put all your points into a single list again (either use Flatten or a Path Mapper), or you can choose to generate different random lists (one for each column) each with a different seed.

The data matching options have disappeared, as they were a sledge hammer approach that didn't solve the problem in many cases. There are now specific components for ShortestList, LongestList and CrossReference that need to be inserted before the actual component:

Above shows how it used to be done, below how it's done now. The benefits of the new approach are:

You can choose which inputs need to be affected by the SL, LL or CR operation.
You can combine multiple data matching operations in series or parallel.
There are a number of different flavours of SL, LL and CR now, upping the total number of matching algorithms to 15.
SL, LL and CR behaviour is no longer hidden behind a context menu.
There is no longer an additional mechanism for doing something in Grasshopper.

For a more in depth discussion on Cross Reference, see this page. For more info about Shortest and Longest List components, see this page.

David Rutten

david@mcneel.com

Poprad, Slovakia

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