Maps UVs onto a subdivision surface by projecting along a direction.
Subdiv Surfaces > Texture > Planar Mapping >
By default, Smart Fit is turned on, which automatically positions the projection manipulator. If you prefer to specify exact values for the projection manipulator, you can turn off Smart Fit and change the values in the Projection Center, Rotation, Width, and Height settings instead.
Choose an axis so that the projection manipulator is aimed at the majority of the object’s faces. For example, a turtle model sitting on the grid would have most of its faces pointing toward the Y axis, while a horse model standing on the grid would have most of its faces pointing toward the X or Z axis.
If most of the model’s faces point somewhere that is not directly along the X, Y, or Z axis, you can choose Camera. This option positions the projection manipulator based on the current active view.
The Insert Before Deformers option is relevant when the object has a deformation applied to it. If the option is turned off and the deformation is animated, the texture placement is affected by the change in vertex positions. This leads to “swimming” textures.
Turning this option on applies the texture placement to the object before the deformation is applied to it. Basically, the texture placement dependency graph node is inserted before the deformer dependency graph nodes and the texture “sticks” to the geometry even after the deformation.
If Smart Fit is turned off, the following options become available. You can enter values to change the Projection Center, Rotation and Scale. After you project a texture, you can change these values from the Channel Box or the Attribute Editor, or use the corresponding manipulator handles to interactively adjust the map.