Radial

The core model is not Zoom or Transform Scale. A uniform scale applies one geometric transform to the layer; Radial resamples pixels relative to a selected Center, so the deformation reads as a local dent, bulge or radial stretch around that point.

Blackmagic places Radial in the Resolve 21 Krokodove Image Warp Tools and describes it as moving pixels radially away from or to the center instead of scaling them, creating a dent distortion. That is the reliable semantic contract; this article does not extend it with undocumented mathematics.

Center X/Y defines the radial origin. In the captured Resolve 21 Controls Inspector both values are 0.5, providing a confirmed center-frame baseline. Keep that baseline first, then move Center deliberately so the point-driven nature of the warp becomes obvious.

Radial Offset is the main Controls parameter for changing the radial geometry. Its captured neutral value is 0.0. Blackmagic documents both directions—toward and away from the center—but the short public guide does not assign a sign to either direction. Verify the sign once in live Resolve on a high-contrast test pattern before labeling it in a preset or workflow.

Because the sign convention is not documented in the brief guide, avoid rules such as 'positive always means outward.' A safer diagnostic is to move Center off-axis, change only Offset to a small positive value, then reverse only the sign and compare both results around the same Center.

The Render tab is a separate layer from Controls. The captured Inspector shows Warp 1.0, Under-Sample Resolution 1, Filtering Area and Edges Black. These values are useful confirmed UI baselines, but they do not reveal Krokodove's internal rendering formula.

Warp exists as a dedicated Render slider, yet Blackmagic's brief public description does not define its internal mathematics. Treat it as a render-level warp control and evaluate it by comparison at fixed Center/Offset instead of presenting an unsupported linear multiplier formula.

Under-Sample Resolution is also visible in the real Inspector while the exact algorithm is not public. Treat it as a quality/performance control: keep a stable baseline, change it independently, and inspect fine text, grids and high-contrast edges at full Viewer resolution and in motion.

Filtering offers three captured choices: None, Pixel and Area. This is a resampling layer. It should not be used to repair a misplaced Center or excessive Offset; establish the dent geometry first, then decide how pixels should be reconstructed.

Area is selected in the captured Resolve Inspector and is a useful neutral comparison point for ordinary video and graphics. None and Pixel are valuable diagnostics on grids, pixel art and hard edges. Make the production choice on the same frame at 100% Viewer scale.

Edges offers Black, Wrap and Duplicate. These modes become relevant when the warp samples outside the source raster. Black makes the boundary explicit, Wrap reuses the opposite edge, and Duplicate extends boundary pixels. None of them replaces sufficient overscan or a sensible deformation amount.

Radial remains a one-input image processor. It does not require a second image like Push and it is not a compositor. One RGBA branch enters Image, is resampled, and leaves through Output; compositing with a plate or another layer happens separately through Merge.

The node is useful for impact dents, stylized optical pulses, abstract procedural textures and map deformation. It is not a physical lens model. For calibration, barrel/pincushion correction or real-lens matching, use LensDistort/LensDistortion and the appropriate lens workflow.

Radial is also not RadialBlur. Radial changes pixel coordinates as a warp, whereas RadialBlur accumulates/smears samples around a center. They can look related in motion design but are technically different operations with different failure modes.

If Center must follow a moving subject, Radial performs no tracking by itself. Solve the movement with Tracker/PlanarTracker or another data source, then link or animate Center. This keeps tracking and warping as separate responsibilities.

With strong Offset values, inspect Alpha as well as RGB, especially on transparent graphics. The captured Controls show no Radial-specific alpha control, so transparency should be treated as part of the resampled RGBA stream rather than as a hidden special parameter.

Animation should be judged at the midpoint as well as the endpoints. Intermediate frames are where aliasing, boundary behavior and an overly aggressive dent often become obvious. Tune timing/easing only after the static geometry is understood.

The most useful discipline is to keep Controls and Render conceptually separate: Center + Radial Offset define the meaning of the deformation; Warp/Under-Sample/Filtering/Edges define its render/resampling path. Once those layers are separated, Radial is straightforward to tune and debug.