A method for video coding is provided. The method includes: partitioning video pictures into a plurality of coding units (CUs), at least one of which is further portioned into two prediction units (PUs) including at least one triangular shaped PU with a partitioning orientation in one of: from top-left corner to bottom-right corner, and from top-right corner to bottom-left corner; constructing a uni-prediction motion vector candidate list; determining whether a current CU is coded as triangle prediction mode according to coded information; signaling a partition orientation flag indicating the partitioning orientation; and signaling index values that indicate selected entries in the constructed uni-prediction motion vector candidate list.