Set the Preview FX preference when working with clips on the timeline.
- Cache Preview FX button
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Enable to cache frames already rendered on the timeline when frame-stepping through effects.
- Soft Effects Rendering option box
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Set to either Layer Based Render to render one layer at a time, beginning with the entire bottom layer, or Frame Based Render
to render the layers in each frame before rendering the next frame (this option may slow down rendering time).