Uniform uses selection to control the influence of its tools over a surface. Other software, specially the ones focused on sculpting, use the concept of “mask” for this purpose. Instead, Uniform follows the standard of illustration and painting software. Parts of the surface that are selected can be edited, unselected parts can not. By default, everything is selected.

You can use the surface selection tool to edit the selection. Draw over the mesh to create a selection.

If you start dragging from outside the mesh, you can perform a clipping selection. Drag to create a box selection. Notice how Uniform is also drawing the full path you are drawing with your pencil. If you close the path, it will become a lasso selection.

Draw a straight line downwards outside the model to invert the selection. Draw the line upwards to select everything.

The way selection is visualized changes depending on the surface view. If you are using a surface view that focuses on shapes, selection will be rendered as a black/white gradient, where unselected areas will be darker. If you are using a color focused surface view, selection will be rendered as contour lines to avoid interfering with the painted colors.