Reflection prediction and across-parallelogram prediction in polygonal mesh compression

A method for encoding a mesh, the method comprising:

• determining one of an across-parallelogram prediction and a reflection prediction to predict a position of one of a current vertex of the mesh and a current point of a two-dimensional (2D) map that is associated with the mesh;
• predicting the position of the one of the current vertex of the mesh and the current point of the 2D map using the one of the across-parallelogram prediction and the reflection prediction;
• determining a context to encode the one of the across-parallelogram prediction and the reflection prediction based on whether a previously encoded position is encoded using the across-parallelogram prediction or the reflection prediction;
• and
• encoding a syntax element indicating the one of the across-parallelogram prediction and the reflection prediction using context modeling with the determined context.

A method of processing a mesh, the method comprising:

• processing a bitstream of the mesh according to a format rule,
• the bitstream includes a syntax element indicating one of an across-parallelogram prediction and a reflection prediction to predict a position of one of a current vertex of the mesh and a current point of a two-dimensional (2D) map that is associated with the mesh, and
• the format rule specifies that
• the one of the across-parallelogram prediction and the reflection prediction to predict the position of the one of the current vertex of the mesh and the current point of the 2D map is determined based on the syntax element;
• and
• the position of the one of the current vertex of the mesh and the current point of the 2D map is predicted using the determined one of the across-parallelogram prediction and the reflection prediction.