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UV Flatten tries to preserve shapes/polygon angles when mapping the 3D mesh to flat UV coordinates. You can choose from two different flattening methods - the Least Squares Conformal Mapping (LSCM) method and the Angle Based Flattening (ABF) method.
UV Flatten has an interactive mode. The features available in the interactive mode depend on the method of the flattening.
This node will add the UV texture attribute to the geometry.
You can manually specify "seams" along which the node will cut the geometry into pieces for flattening. This lets you split the surface into manageable sections to make it easier for the node to flatten.
If the polygonal surface has an edge group named
seams, this node will use it to cut the geometry. You can select additional seams interactively when the node is selected.
Features available when flatten method is LSCM
When flattening using the LSCM method,
You can pin certain vertices to fixed UV coordinates.
You can interactively add pins, and select multiple pins and move them while the node maintains the positions of unselected pins, when the node is selected.
You can force groups of vertices to align horizontally or vertically
You can interactively add groups of vertices, and get all vertices in a group to either have the same U-coordinates or the same V-coordinates.
Features available when flatten method is LSCM
When flattening using the ABF method,
You can straighten an edge loop
You can interactively select groups of edges. Each group of edges will be straightened.
You can have edge loops to be straightened detected automatically
You can let the UV Flatten node automatically decide which edge loops to straighten. This node tries to straighten as many edge loops as it can while ensuring that the straightening does not cause an impossible topology.
You can get quads in the geometry to become rectangular in the flattening
UV Flatten scales the pieces to fit within the unit square (u of 0 to 1, v of 0 to 1), while maintaining their proportions relative to each other.
Using UV Flatten
Select the primitives (faces) you want to add UV coordinates to.
Click the UV Flatten tool on the Texture tab.
Select the edges to use as seams, and press Enter to confirm your selection.
In the viewer, press Space + 5 to switch to "UV Viewport" to see the flattened texture pieces.
To draw the default pins when the tool is active, set the node to export an Active Pin Group.
Move a pin
Click the "Manipulate pins" button in the toolbar. Select a pin or multiple pins to move, and drag.
Add a pin
Click the "Pin vertices" button in the toolbar. Select the vertex or vertices you want to pin and press Enter.
Cut an edge
Click the "Cut edges" button in the toolbar, select the edges, and press Enter to confirm the selection.
Once your texture pieces are unwrapped, you can use the UV Layout node to change the packing of the pieces.
The name of the texture coordinate attribute to flatten, defaulting to
The primitives to add UV texture coordinates to. If this is empty, the node applies to all incoming primitives.
An edge group containing the initial seams to use to split the geometry into texture pieces. The node automatically considers boundary edges, edges between inconsistently oriented polygons, and edges between more than two polygons as seams.
An edge group containing the
When you add seams interactively, the node puts them in this parameter. The initial seams you selected when you first used the tool are in the Seam group parameter. The node keeps these separate to preserve the positions of the pieces as you cut. If you edit Seam group (for example, by cutting and pasting the contents of Additional seams into it), the node will re-pack the pieces.
Use Existing UV Coordinates
If the geometry already has texture coordinates, ignore the 3D geometry and flatten any existing UV coordinates instead.
This may be useful to let you use this node’s interactive mode to edit existing UV coordinates while minimizing distortions.
Use Existing Boundary UV Coordinates
If the geometry already has texture coordinates, for the boundary points, use existing UV coordinates as UV coordinates of the flattening. Assign UV coordinates to non-boundary points to minimize distortion.
This parameter is only available when the flatten method is ABF.
If Straighten Boundary is selected, the boundary edge loops of the texture pieces are identified and straightened.
If Straighten And Orthogonalize Boundary is selected, the boundary edge loops are straightened. Two boundary loops that meet are made to meet perpendicularly.
If Straighten Boundary And Interior is selected, the boundary edge loops and a maximal number of interior edge loops that can be straightened are identified and straightened.
If Orthogonalize is selected, a maximal set of edge loops to be straightened is identified and straightened. Of the straightened loops, some are oriented horizontally and others are oriented vertically. Selecting this option will produce a flattening in which quads are rectangularized.
The list of interactively pinned vertices.
The list of vertex groups.
Each vertex in a vertex group represents a directed edge. A vertex of a polygon with n sides, having vertex offset v, represents the directed edge from v to (v + 1) % n. When the flatten method is LSCM, you must choose, for each vertex group, a direction to align the group in. Choose between directions U and V.
When the flatten method is ABF, all directed edges represented by a vertex group will be straightened.