Houdini UI Tips! Transform Node vs Edit Node

I often interchange between using the Transform node and the Edit node in Houdini and I was asked in the comments on one of my Youtube tutorials, why I choose the Edit node over the Transform node?

Houdini Transform Node Gizmo tool

TIP: To activate the widget gizmo tool, select the transform node, hover the mouse of the 3D viewport and press enter on the keyboard.

Houdini Transform Node Gizmo tool still located at origin and not at the sphere

Transform Node

Let’s see what happens when the sphere isn’t located at the center (origin).

Since the sphere isn’t at the origin, we can clearly see the widget gizmo is still located at the origin after we selected the transform node. The only difference between the this scenario and the above is that the sphere is now moved.

Pivot Point on Selected Geometry

Say we want to use the transform node and rotate the sphere (have the Transform widget gizmo on the sphere, we need to:

1. Select the Transform node or Edit node (This actually works for both)

2. Mouse hover over 3D viewport, press enter

3. At the top of the 3D viewport, select 3D geometry (THIS IS THE KEY STEP)

4. Now click the sphere

Houdini’s Edit Node Gizmo is pivoting at the sphere

As seen on the screenshot on the right, the gizmo is focused on the center of the sphere and not at the origin.

This way of transforming, rotating and scaling the geometry is extremely handy when you’re trying to position things interactively in the 3D viewport for stuff like 3D modeling.

Sorry that this screenshot of the Edit Node, I should have did a screenshot of the Transform Node, but it will look exactly the same thing.

Edit Node

So at first glance the Edit Node and Transform Node seems to function exactly the same thing, but there is a difference. The selections and actions within the Edit Node are cumulative. In order to illustrate this, let’s make a few more modifications to the sphere geometry…

Transform Node vs Edit Node

All actions done with the Edit Node are cumulative and everything done under the Transform Node applies to that one selection we make at the beginning.

What does that mean?

If I select some polygons to move to the right with the Transform Node, it’ll move those polygons.

What if I want to move a 2nd set of polygons upwards to make an L shape?

I would require 2 Transform nodes to do this.

Edit Node is Different

This is different from the Edit Node, I can push and pull polygons anywhere to make that L shape mesh with a single Edit Node.

Manually Change Pivot Point

Transform Node Parameters in Houdini

With the Transform Node we can rotate objects around the origin position by default, but what if you wanted to rotate around another object? We’ll need to change the pivot position. We do have a parameter to change the pivot position inside the Transform Node, but what if I just want to eye ball it in the 3D viewport?

Apostrophe key

The key is the apostrophe button on your keyboard. When you’re in that widget tool mode in the 3D viewport, press apostrophe and the widget will change. If you translate this position, you’ll notice nothing happens. But in reality you’re changing the pivot position.

Take a look at the short video for clarity.