user: Describe Options from the Blender manual or Python API, including usage steps and snippets.

assistant: Source
:   Mesh object to copy data from.

    Object Transform
    :   Whether take into account the world space transformations of the source and destination objects.
        When unchecked, the modifier acts like both objects are in the same position and have
        the default rotation and scale.

Mix Mode
:   How to combine the new data from the source mesh with the original data in the destination mesh.

    Replace
    :   Interpolate between the original and new value using *Mix Factor*.

    Above Threshold
    :   Replace the destination value if it’s greater than or equal to *Mix Factor*.
        In the case of multi-component data like colors, the threshold is compared to the average of
        these components.

        For boolean data like *Freestyle Mark*, you can use this to perform a logical AND:
        simply ensure the *Mix Factor* is 0.5 or greater, and the destination mesh will only have
        marked edges/faces that were already marked and are also marked in the source mesh.

    Below Threshold
    :   Replace the destination value if it’s less than or equal to *Mix Factor*.
        In the case of multi-component data like colors, the threshold is compared to the average of
        these components.

        For boolean data like *Freestyle Mark*, you can use this to perform a logical OR:
        simply ensure the *Mix Factor* is 0.5 or greater, and the destination mesh will have
        marked edges/faces that were already marked or are marked in the source mesh.

    Mix
    :   Mix the source value with the destination value, e.g. performing an alpha blend in the case
        of color attributes. Then, interpolate using *Mix Factor*.

    Add
    :   Add the source value to the destination value, then interpolate using *Mix Factor*.

    Subtract
    :   Subtract the source value from the destination value, then interpolate using *Mix Factor*.

    Multiply
    :   Multiply the source value by the destination value, then interpolate using *Mix Factor*.

Mix Factor
:   Interpolation factor between the original destination value and the newly calculated value.
    If *Mix Mode* is *Above Threshold* or *Below Threshold*, this is a threshold value instead.

Vertex Group
:   Allows per-element control of the *Mix Factor*.

    Invert
    :   Invert the weights of the vertex group (change them to 1 - weight).

Generate Data Layers
:   Click to add any missing data layers, e.g. vertex groups that exist on the source mesh but not
    yet on the modified mesh. The modifier doesn’t do this automatically, so make sure to click
    this button (or add the missing layers yourself) as the transfer may not work otherwise.

    Layers added this way will stay behind when removing the modifier.

Data Types
:   The toggle buttons *Custom Normals*, *Colors*, *UVs* etc. indicate which data
    should be transferred.

Mapping
:   How to find the matching source element(s) for each destination element.
    The various options are explained in the [Mapping](#mapping) section below.

Layer Selection
:   Which source layers to copy to the destination mesh (e.g. all vertex groups
    or a specific vertex group).

Layer Mapping
:   How to find the destination layer for a given source layer: by name or by order.

Islands Precision
:   Controls the calculation that prevents a destination face from receiving UV coordinates from
    disparate source UV islands (areas bordered by [seams](../../meshes/uv/unwrapping/seams.xhtml)).
    Keeping this at 0.0 means no island handling at all, while higher numbers increase the correctness
    of the result at the cost of extra computation.

    Typically, small values like 0.02 are enough to get good results, but if you are mapping from
    a very high-poly source towards a very low-poly destination, you may have to raise it quite significantly.