If you have a filled circle on one layer and a wavy line cutting through it on another, and you want to fill the area between the wave and the bottom of the circle without merging the layers (for animation purposes), you can use a clipping mask. First, duplicate the circle layer and place the duplicate above the wave line layer. Then, create a new layer above the wave line, and set it as a clipping mask to the duplicated circle. Now, when you draw or fill between the wave line and the circle’s bottom edge on the clipped layer, the color will stay confined within the circle shape. This approach preserves layer separation while allowing you to fill the desired area. Alternatively, you can manually select the area using the Lasso tool on a new layer and fill it, but the clipping mask method is more efficient and animation friendly.Hope this helps.
... View more