Monday, October 8, 2012

Dynamo - Sine Wave Points

Last Dynamo ‘Create Points’ example, porting ‘Sine Wave Points’ from Nathan Miller’s Proving Ground Wiki, Create Points page.

PG 1.4

This is the trickiest example so far. The two Build Sequence nodes at bottom left create the X and Y values. The Cartesian Product node applies the function ‘comb’ to each pair of XY values. I’ve created the function as a couple of User Nodes, and then Mapped the output into the XYZ Scale node to scale the grid up by 10x.

As an aside, note the difference between Cartesian Product and Combine nodes. Cartesian gives {X1Y1, X1Y2, X1Y3, … X2Y1, X2Y2, … XnYn} which makes a grid; while Combine gives {X1Y1, X2Y2, X3Y3, … XnYn} which would just make a line. More info: Cartesian Product on Wikipedia.

Regarding the User Nodes: I tend to use them to wrap custom code for easy testing. If you build a big plate of spaghetti, it’s very hard to tell what’s not working properly. If you break the code into ‘User Node’ chunks, you can test each piece in isolation to make sure it works. Also, with the Map-like nodes, I prefer to feed them a User Node function because it’s clear how the inputs are going to be mapped. I’m not even sure some of my Mapped functions could be made without User Nodes.

Anyhow, this example uses two User Nodes. First up is cos(x)+sin(y):

cos(x) sin(y)

Which very obviously does what it says on the tin.

Next is XYZ - z=f(xy), which I’m quietly pleased with:

XYZ - z=F(xy)

This uses the input function f to generate a z value from the input x and y values, and then outputs an XYZ object. I wasn’t sure whether you could pass a function into a User Node like this. It’s great that you can, since it makes the initial layout much more flexible: Just substitute a different function in place of cos(x)+sin(y) to generate a different set of z values for the grid.

I’ve used an Apply here rather than a Combine, since the node will only accept one pair of xy values at a time. If you wanted a node that would accept list inputs, you’d also need to Combine the XYZ. I’ll post an example when I find an application.

Here’s the source: Dynamo Definition PG 1.4c Sine Wave The zip file contains both the .dyn file and the two User Node .dyf files. Open each of the .dyf files in turn to load them into Dynamo’s library, and then open the .dyn.

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