Stretch

Stretch belongs to the Krokodove warp tools integrated into DaVinci Resolve 21 and Fusion 21. Blackmagic summarizes it as pixel stretch along a specified line: the image is warped directionally instead of being uniformly scaled as one raster layer.

The primary Inspector control is Type. The captured Resolve 21 menu exposes exactly two modes: Source and Destination and Source and Offset. They are construction models, not quality presets.

Source and Destination is the clearest mode for diagnosis. Source Start/End define the original segment and Destination Start/End define the target segment. Stretch builds a warp that maps image geometry relative to the source line toward the target line.

When Source and Destination coincide in position, length and angle, the result is close to neutral. This is the best baseline before authoring deformation: first prove the near-pass-through state, then move one endpoint at a time.

A longer Destination generally produces extension along the mapping while a shorter one produces compression. Rotating the destination segment introduces rotation/shear-like character together with the stretch.

Source Start and Source End are not crop boundaries and are not a mask. They define the geometric reference segment from which the warp is calculated.

Destination Start and Destination End are not ordinary Center/Size controls. They define the new target segment, so moving the two endpoints differently can create an asymmetric pull or diagonal deformation.

The captured Controls panel shows Source Start (0.0, 0.5), Source End (1.0, 0.5), Destination Start (0.0, 0.5) and Destination End (1.0, 0.5). This is UI evidence for one saved state and a useful neutral baseline, not a universal factory-default contract.

The captured coordinates are presented as normalized X/Y values. A horizontal line through Y=0.5 is useful for teaching because deformation direction remains obvious before any diagonal component is introduced.

Source and Offset is the second documented Type. The legacy Krokodove node reference confirms the label, but the article capture does not show its expanded conditional state, so this reference does not invent hidden field names without a live target-build capture.

Practically, Source and Offset offers an offset-driven construction relative to the source line instead of requiring the full explicit destination segment. It is useful for quicker motion-design setup, but its conditional UI should not be assumed to be identical to Source and Destination.

Stretch consumes a regular 2D image stream such as MediaIn, Loader, Text+, Background/Merge output or another raster branch. Native Shape data should be rasterized through sRender before entering this image-warp stage.

The optional Effect Mask is a separate blue mask input. It gates the spatial contribution of the completed Stretch effect and is not a second image map, displacement map or intensity map.

Effect Mask also does not define the Source/Destination line. Warp geometry lives in Controls; the mask only controls where the result contributes. Treat those as separate diagnostic layers.

Output remains a normal RGBA image stream, so downstream Merge, Transform, Blur, Glow, Color Corrector and other 2D image tools work normally.

Stretch differs from Directional Scale. Directional Scale performs directional scaling through its own axis/angle model, whereas Stretch explicitly maps line geometry.

Stretch also differs from Shear. Shear changes angular relationships through a shear model; Stretch ties deformation to source/target segment geometry.

It differs from Displace as well: Displace consumes a separate image map, while Stretch does not require a second image map because its mapping is authored with Inspector endpoints.

Text and graphics are excellent diagnostic sources because straight glyph contours reveal immediately when source or destination geometry is poorly chosen.

On live action, aggressive Stretch can damage faces, architecture and high-frequency texture quickly. Start with moderate endpoint movement and inspect at Viewer 100% rather than judging only Fit view.

Alpha is warped with the RGB image state. Semi-transparent titles, glows and antialiased edges should therefore be checked in the Alpha Viewer as well as RGB.

For transition work, animate one clear endpoint or variable first. Keyframing all four points simultaneously can make the motion impossible to diagnose.

A practical elastic pull keeps Destination Start anchored and animates only Destination End. This preserves causality and leaves room for later easing or downstream Motion Blur.

Node order matters. Transform before Stretch changes the source geometry that line mapping receives; Transform after Stretch moves the already-warped raster. Those are not equivalent arrangements.

A matte baked into the image before Stretch is also different from the node's Effect Mask. Upstream alpha changes the source image itself while Effect Mask only gates the node contribution.

At strong settings, inspect image boundaries. Line warps may stretch edge pixels or expose empty regions depending on the source and downstream crop, so evaluate the maximum deformation at delivery raster size.

The captured Type menu proves two modes only. Do not add imagined third-party presets or controls that are not present in the reviewed target state.

For reproducible templates, document Type and all endpoint pairs. A note such as 'stretch right' is not enough because different source/destination geometries can create similar still frames but very different animation behavior.

A reliable production QC order is topology → Type → neutral source/destination baseline → one endpoint → the other endpoint → Effect Mask → alpha/edges → playback.

The core model is simple: Stretch is not a global scale. It builds a directed pixel warp around a line; Type chooses the construction, endpoints define geometry, optional Effect Mask defines coverage, and Output stays RGBA image data.