What is Compositing?
Compositing combines visual elements from separate sources into a single image or video frame. Positioning, masks, transparency, blending, and effects determine how the layers interact.
How Compositing works
Digital compositing evaluates a stack or graph of foregrounds, backgrounds, masks, mattes, and effects to calculate final pixels. Alpha and blend operations determine coverage and interaction, while transforms and tracking align elements in space and time. Convincing integration also requires consistent perspective, motion blur, grain, lighting, and color management. The composite is usually created during finishing and then rendered into a master or delivery derivative.
Key facts
- Premultiplied RGB already includes alpha coverage; treating it as straight color during filtering or resizing can produce dark or colored fringes around transparent edges.
- Chroma-key extraction creates a matte rather than simply deleting green pixels, and spill suppression is a separate operation needed to neutralize reflected screen color.
- Compositing transfer-encoded values with ordinary arithmetic can produce incorrect edge brightness; linear-light operations better model additive light for many blends.
When Compositing matters
Use compositing to add backgrounds, watermarks, titles, product mockups, or visual effects. Mismatched color spaces, premultiplied alpha, lighting, or edge treatment can make combined layers look incorrect.