UV Slots, Cards and Export

Once the atlas is baked, each bstrand’s patch of it becomes a hair card. UV Slots decide where those patches are, Cards builds the meshes, and Export & Save writes everything out.

UV Slots

A UV slot is the rectangle of the atlas one bstrand occupies. By default it fits the bstrand automatically: its outline as seen by the bake camera, plus the strand thickness and the Card Margin. Slots are drawn as violet boxes in the viewport.

Violet slot boxes with slot numbers around several bstrands, and a green frame around a grouped pair.

Control	What it does
Card Margin	Extra room around every slot and card. Raise it if you will bend the cards later and strands would reach the edge.
UV Slot	The active bstrand’s position in the exported layout. −1 is automatic, which follows the order of bstrands in the scene.
Slot Offset X / Y	Slides the slot, and its card, across the atlas.
Slot Scale X / Y	Grows or shrinks the slot about its centre, taking in more or less of the atlas around the strands.
Eye	Shows or hides the slot boxes.
Edit Card Slots	Drag slots directly in the viewport (see the hotkeys below).
Slot Names	Labels each slot with its bstrand’s name.
Reset (arrow)	Puts the active slot back on its automatic fit.
Group / Ungroup	Gives the selected bstrands one shared slot, or separate slots again.

Group bstrands into one slot

Select two or more bstrands and click Group. They now share one slot around all of their hair: one green frame, one card and one entry in the exported layout. Slot number, offset and scale are shared by the group. Select any member and click Ungroup to give it its own slot again.

Use groups for elements that belong on one card, such as a lock and the flyaway hairs you built beside it.

Edit Card Slots hotkeys

Key	Action
LMB drag	Drag a corner to scale; drag inside to move
Shift + drag	Scale from a corner while keeping the aspect ratio
R	Reset this slot to its automatic fit
Tab	Step to the next bstrand
Enter	Confirm
Esc or RMB	Cancel

Cards

Control	What it does
Quad X / Quad Y	The size of one quad of the card mesh, in metres. Every card gets as many loops as fit, so all cards share the same density. The line below shows the active bstrand’s card size and loop count.
Create UV-Ready Cards	Builds one card per slot. Each card is the size of its slot seen from above, lies flat on the atlas plane, and is UV-mapped to its patch of the atlas.
Preview Card	Builds one card next to the bake zone wearing the maps you just baked, to check they work together.

If the maps are already baked, the cards wear them straight away: Albedo darkened by Ambient, Alpha as the cut-out, Normal and Depth for relief, plus Specular and Translucency. If nothing is baked yet the cards are built bare. Bake, then create them again.

UV-ready cards wearing the baked atlas, beside the original strands.

Export & Save

Baked maps

Control	What it does
Output Folder	Where maps are written. The default `//` means the folder the .blend is saved in. If the file isn’t saved yet, the panel shows where the maps will go instead.
Name Prefix	The start of every file name (default `BStrands`), for example `BStrands_albedo.png`.
Create Subfolder	Writes the maps into a subfolder named after the prefix.
Format	PNG, TGA, OpenEXR, JPEG, TIFF or WebP.
Open Output Folder	Opens the folder in your file browser.

Meshes and files

Control	What it does
Sides	Cross-section of Convert to Mesh: 2 is a flat ribbon facing the bake camera; 3 or more builds round tubes.
Convert to Mesh	Turns the active bstrand into a UV-mapped mesh, including sculpt edits and painted colour. The bstrand is hidden (untick Hide Source bstrand to keep it visible). Use it for Vertex Paint or to export strand geometry.
Export Selected Meshes	Writes the selected meshes to the output folder as FBX, OBJ or glTF 2.0.
Export UV Layout (AHC)	Writes each slot’s place in the atlas as a JSON file for Agile Hair Cards.
Save Project	Saves the .blend with every bstrand, modifier and curve.

Using the atlas with Agile Hair Cards

Agile Hair Cards (AHC) is the companion add-on that cuts hair cards and places them on a character. Curve-BStrands writes the layout file AHC already reads.

Bake the maps.
Click Export UV Layout (AHC) and save the JSON file. By default it is named <Name Prefix>_uv_layout.json and goes in the output folder.
In Agile Hair Cards, select your guide mesh and use Import UV Layout with that file.

Each UV slot becomes one AHC atlas slot, in slot order. The file also lists each bstrand’s name, strand count and pixel rectangle, as a record of the bake.