Grid Warp

Grid Warp draws a grid of handles over the photograph. Drag the handles and the picture bends smoothly with them. It is a geometry adjustment like Straighten: it reshapes the frame before every mask, stroke and layer, so anything you paint afterwards lands where you painted it. The edit is non-destructive and lives on one Grid Warp node in the chain's geometry, right after Lens. The section sits directly below Geometry.

Grid Warp is a Pro feature. Arming the tool does not switch the section on; moving a handle does, the way moving any control switches its section on, and the first drag on a photograph builds the node switched on.

The grid

A photograph starts with four columns by three rows across a landscape frame, three by four down a portrait one. The intersections are the handles.

Column and Row are numbers you drag: drag sideways to change them a step at a time, or click without dragging to type one. The warp is kept: the new handles take the field's value where they sit, so a denser grid adds control without starting over.
The link button beside Column ties the two together: with the link on, a change to one is the same change to the other.
Alt-click on open grid adds a column and a row through that point, which is how you put handles exactly where they are needed. Alt-click a line takes it out. The frame's own edges stay.

Picking handles

Click a handle to pick it; Shift-click adds one or takes one out of the pick.
Drag on the grid to marquee several. Shift with the marquee adds to the pick.
All, None, Grow and Shrink in the section: Grow takes in every neighbour along the grid, Shrink drops the pick's rim, the frame's edge included.

Moving, twisting and pinching

Drag a picked handle to move the whole pick.
Twist is a wheel in the section: drag round it and the pick turns about its centre, as far round as you like, with the angle read out below it. Shift snaps to fifteen degrees. With Influence above zero, twisting a single picked handle twists the picture around it.
Pinch is a pad in the section: drag from its centre and the pick pulls out or pinches in about its centre. Right makes it wider, left narrower, down taller, up shorter, and a diagonal does both. The further you pull, the more; there is no limit. Shift keeps it uniform. The readout below shows the width and height as percentages.

The two sit side by side under Edges and grow with the panel.

Both spring back to rest on release, so every drag starts fresh, and each drag is one undo step. They work on whatever is picked, and sit idle until something is.

The picture redraws under the pointer as you drag, from the canvas or from the section. On release the engine renders the warp properly, at full quality, and the 1:1 view stays sharp.

Influence

Influence is how far a drag carries past the picked handles, in grid steps. At zero only the pick moves. At one the neighbouring handles come along at half strength, at two the next ring out comes too, and so on, fading with distance. It is a property of the drag: set it, then drag, and that drag uses it.

Heat shows the influence before you move anything, with three icon buttons:

Luma (the half-filled circle): picked handles white, fading through grey to black past the influence.
Chroma (the red and blue circle): picked handles red, cooling to blue past the influence.
Off (the struck circle): picked handles white, the rest grey, no falloff shown.

The heat is on the handles only. The photograph between them stays as it is.

The lines' colour

The grid lines take the opposite of the photograph: the complementary hue of its average colour, dark on a light picture and light on a dark one, and plain grey on a grey picture. That is the automatic choice, and it is what you get on every photograph until you say otherwise.

The Hue and Luma sliders under Lines take over from it, and the swatch beside them shows the colour in use. Auto hands the choice back to the photograph.

The choice is one for every tool that draws lines over the photograph: Shape Warp's rings and the Radial layer's gizmo take the same colour, and their Lines rows set the same thing.

Edges

Where the picture pulls away from the frame, Stretch carries the border pixels in to cover the gap, which is what a subtle reshape wants. Transparent leaves the gap empty so a crop can take it off, or a Finish layer underneath can show.

Reset

The section's Reset puts every handle back to rest. The grid keeps its density.

Keys

Shift+G arms and puts away the tool.
Enter keeps the warp and puts the tool away.
Escape puts the mesh back the way it was when the tool was armed, and takes the node out again if the tool built it.

Notes

Copy Edits and presets leave the mesh behind: it describes one photograph's frame and content.
Changing the photograph, the pick, or the tool during a drag cancels its uncommitted preview, and closing the section cancels a wheel or pad drag. If the window loses focus mid-drag, the drag ends where it stands.
Re-cropping after warping moves the grid relative to the content, since the grid is measured against the cropped frame.
The main Graph inspector shows the section controls for the tool's node. A popped-out inspector shows the grid counts and wiring guide.
Very strong pulls can fold the grid onto itself. Such a fold has no unique inverse and can show seams or abrupt changes; reduce the pull to keep the grid from crossing itself.
Inserting a line samples the existing warp onto a new grid. Between handles the curve can change, especially with uneven spacing. Removing that same new line restores the old handle values.