Use the resolution menu in the compositing viewer’s toolbars to cook at different scale factors of the image resolution, from 12.5% to 800%. Reducing the image resolution results in faster cooking.

In a compositing viewer, hold ⇧ Shift and drag a box around the part of the image you're interested in.

To return to the full image, click the Clear Selection button (on the Adapt toolbar) or hold ⇧ Shift and click black space outside the image.

When you drag a handle or parameter slider, the image automatically scales down to a much lower resolution (by default, a quarter of the current resolution) . When you release the mouse button, the image returns to its normal resolution and does a longer cook.

You can specify the resolution reduction factor, the minimum image resolution to enable this mode and other options in the Compositing Preferences. Choose Edit ▸ Preferences ▸ Compositing to open the Compositing section of the Houdini Preferences window. Click the Interactive tab and set the Interactive Rendering Fraction.

When Incremental mode is enabled, as tiles are cooked, the image in the viewport is updated. The image starts out as a dull gray and slowly gets filled in by the cooked tiles.

Click an area to cook that area of the image immediately. Press ⎋ Esc or click RMB in the viewport to interrupt cooking at any time.

To turn off image updates during cooking, choose Edit ▸ Preferences ▸ Compositing to open the Compositing section of the Houdini Preferences window. Click the Interactive tab and set Cooking feedback to None or Progress Bar.

See how to turn off automatic cooking.

COPs that are bypassed do not make a copy of input data. Similarly, if an operation is only scoped to affect the Color plane, any other planes will be “passed through” the COP without any copying or cooking.

Timing and management COPs (such as Shift or Merge) do not copy image data unless necessary (i.e., the resolution is different, or frames need to be blended together).

Choose Editing ▸ Preferences ▸ Compositing to open the Compositing section of the Houdini Preferences window, and increase the Interactive Cache Size value.

The compositor supports cooking on more than one local CPU, which results in almost halving (two CPUs) or quartering (four CPUs) the cook time.

If you only need the color data, only write out the color plane. You can specify which planes to save in the output driver node and the flipbook dialog.

If you have a multi-processor machine, and your network references data from the previous frame, or your network is small, turn on Batch cook frames in the output driver . This makes the compositor generates two frames at a time.

You can increase the batch rate if you have more than two processors (for example, if you have quad-processor machine you can increase the batch rate to 3 for even better performance).