Modifying Objects Using Lookup Curves

The CrosstalkGeo and LookupGeo nodes offer you direct global control over each of the vertex x, y, and z values respectively. You can, for example, only modify all the y values without touching the x and z values.

You change the different vertex values (x, y, or z) by modifying their associated 2D curves in lookup tables (LUTs). The x axis in the LUT represents the current vertex value, and the y axis the new vertex value.

By default, the curve is a diagonal line where all the points in the curve have the same value on the y axis (the new value) as they do on the x axis (the current value). Because both x and y values are the same, there is no change in the object’s shape.

By modifying, for example, the CrosstalkGeo node’s y LUT the following way, you can set some of the vertex y values of a sphere to 0 to squash its bottom half:

Modifying the CrosstalkGeo node’s LUT.

With the CrosstalkGeo node, you can also use one of the vertex x, y, and z values to evaluate the lookup curve and then add the result to another vertex value. For example, you could modify the x->y curve, using the vertex x value to find the new value on the curve, and then add that to the vertex y value. This way, you can modulate the y values by another channel.

By default, these curves are horizontal lines at y=0. They produce no change, because the value added to the vertex (the new value on the y axis) is 0.

To Modify Objects Using Lookup Curves

1.

Select 3D > Modify > CrosstalkGeo or LookupGeo to insert a CrosstalkGeo or LookupGeo node anywhere after the 3D object you want to modify.

2.

Attach a Viewer to the node to see your changes.

3.

In the node’s controls, use the display dropdown menu to select how you want to view your object in the Viewer while making changes to it.

4.

From the list on the left, select the curve you want to modify. For example, you’d select z to only modify the vertex z values.

In the case of the CrosstalkGeo node, you can also select y->x, for example, to use the vertex y value to evaluate the curve and add the result to the vertex x value.

5.

Adjust the curve as necessary. To insert points on the curve, Ctrl/Cmd+Alt+click on the curve.