A 3D model can be modeled using “pattern-instance” representation, wherein an instance component may be represented as transformation (for example, rotation, translation, and scaling) of a pattern. Quantization errors may be introduced when encoding rotation information, causing different vertex coordinate errors at different 5 vertices of an instance. To efficiently compensate the vertex coordinate errors, the encoder decides a quantization parameter for compensating a vertex coordinate error. The quantization parameter is signaled in the bitstream as a quantization index. The quantization index, a quantization table the indicates a mapping between quantization indices and quantization parameters, and vertex coordinate errors are 10 encoded into a bitstream. The quantization table may be built based on statistical data. At the decoder, the vertex coordinate error is decoded based on a quantization parameter, which is determined from a received quantization index.