Gaffer: Importing Geometry [4/8] (Patreon)

Now that we've covered the Gaffer basics, let's create a more advanced scene. In the upcoming sections of this tutorial we'll import chess set geometry in USD format, pose and animate it, set up studio lighting, author materials in Cycles (including displacement), create an image catalog, and finally render to disk.

Let's get started!

First, download the attached USD scene and extract it to a location of your choice.

In Gaffer, put down a SceneReader node and point the File Name to bhgc_chess_set_usd.usda. This will import the entire scene hierarchy. By default, Gaffer will only display bounding boxes in the Viewer. Loading all geometry in complex scenes can be very slow, so it's better to start with bounding boxes and let the user pick which objects to view fully.

Since our geometry isn't too heavy, we can go to the Hierarchy View and include each part of the scene in the Visible Set.

Now that we can see what we're working with, let's set up a "pose" for the chess set and animate a turntable.

Attach a Transform node to the SceneReader and name it turntable.

Right click on the Y-axis Rotate parameter in the Node Editor and click Set Key.

Jump ahead to frame 12 in the Timeline at the bottom of the screen and type 360 in the same Y parameter.

A new keyframe will be automatically created, so we now have a full rotation happening from frames 1-12. If you scrub through the timeline the chess set isn't moving though. We need to add a Path Filter to tell Gaffer which objects to apply the transform to.

Previously, we dragged objects onto nodes and Gaffer automatically created Path Filters for us. In this case, let's do it manually. In our turntable transform node, click on the Filter tab and click PathFilter in the Filter dropdown. Finally, click the plus icon to add a new path field. This is the final result:

For the turntable we can simply type the wildcard symbol * to include every object in the scene.

We've got movement!

As is the case with animation workflows in other apps, Gaffer defaults to "ease in/out" interpolation. We don't want that on a looping turntable as it will cause the motion to accelerate and decelerate noticeably. Open up the Animation Editor tab and select turntable/transform/rotate/y in the Name panel. Press F to frame our two keyframes in the viewer.

Left click and drag to select the keyframes, then change their Interpolation to Linear. Note that the slope of the curve has changed to a straight line. Now we have an animation that will loop seamlessly.

Next, we can use Transform nodes to create a "pose" for the chess set with some pieces moved around, as if in mid-game. We'll create a transform for each piece we want to move. Each transform will need its own PathFilter, which can be created by dragging and dropping objects from the Viewer or the Hierarchy View, or by entering the path manually. (Be careful to include the entire chess piece objects, including their felt bases. Selecting pieces in the Viewer might only pick up the piece and not the felt.)

I moved 11 pieces here, but feel free to set it up however you like.

Another useful thing we can do is create a Backdrop to make it easy see what parts of the node graph do what. Select all the nodes you want to include, then press tab and add a Backdrop. You can change the title via the Node Editor and change the color by clicking the gear icon and selecting Edit UI.

Because the node graph is procedural and non-destructive we can have an entirely different branch dedicated to posing the pieces and it won't overlap with or interfere with the turntable.

Note that you can easily go back and move geometry that already has a Transform associated with it. Simply select the object in the Viewer or Hierarchy View, reposition, and the changes will be stored.

We've now got several branches to our node tree: the raw imported geo, our turntable animation, and our "game in progress" pose. That should provide a good starting point for eventually rendering our scene, so let's move on to creating Cycles materials in Part 5!