An encoder configured to generate an encoded bitstream for decoding by a compatible decoder, wherein the decoder receives the encoded bitstream with a current picture including a current block having a first partition boundary partitioning the block into first and second non-rectangular regions and a second partition boundary, intersecting the first partition boundary, and partitioning the second non-rectangular region into three portions. Using the encoded bitstream, the decoder determines a first predictor for use within the first non-rectangular region using a first motion vector selected from a first list of motion vector candidates, determines a second predictor for use within the second non-rectangular region using a second motion vector selected from a second list of motion vector candidates; and decodes the current block using the first predictor and the second predictor. Decoding further includes smoothing the first predictor and the second predictor across the first partition boundary.