LSCM means Least square conformal mapp. This is an advanced mathematical method to automaticaly create an UV-mapping while keeping texture stretch and deformations minimals. This method was described by B. Levy (Inria) who had also the kindness to help blender devs to implement by furnishing a library and answering many questions. Blender devs for this are Brecht Van Lommel and Jens Ole Wund.
LSCM try to preserve angles between each face, so the mapping will be very good locally but scale is not preserved. By pinning some vertices, you can control the result and get an all good texture map.
in its most refined form, as described by B. Levy, (publications) LSCM can be a completly automatic method.
Blender support is only the UV-mapping part and require user input, allowing more artistic control.
To be able to correctly unwrap a mesh with LSCM, you must make sure you mesh can be flattened without too much deformations (in mathematical term, it should be equivalent to a disc). This is done by defining seams, ie places where the mesh will be cut. You dont need to add seam if the mesh can be unwrapped directly in a plane.
examples :
- on the left a cube with enough seams and mapping result,
- on the right, not enough seams were defined.
As you can see, no deformations and absolutely correct mapping on the left. To define seams, from edit face mode, select vertex which should form a seam and use menu item : Mesh/Edges/Make Seam
More than one region can be defined by the seams. Each region will need to be independently mapped.
to map a region :
- select a face belonging to it,
- LKEY to select all linked faces,
- UKEY/LCSM to do the mapping.
Let start a more valid example, a low-poly vest.
The first image show what happens when we invoke LSCM without defining any seam. although this is a valid conformal map, it is not really useful, especially for the the sleeves.
So we will define 3 regions, one for the torso part, one for each sleeve.
second image show the result. Here, we have still 2 different problems :
- the sleeves are a tube wich is not analog to a disc so we need to define another seam
- there is some distorsion around shoulder. yet another seam will solve the problem
third image show final result, the face are all well formed and not distorted
Yet to be written
This is still very experimental and only critical features are present.
those enhancements may be done later :
- overlap control.
- better packing in texture space.
- Automatic group creation.