In a data processor and a shading apparatus used in the data processor, the data processor selects an address based on the information of a memory or a translation look-aside buffer. Therefore, even when the same data are accessed, a different address at high speed is adopted according to the hardware, object to be processed, processing, etc. A plurality of geometric vectors are given as the parameters for the vertexes of a picture, the vectors are interpolated in the picture, and the luminance of each small area in the figure is calculated using the vectors generated by the interpolation. Therefore, a spotlight or highlight can be expressed with high accuracy and at high speed even when the amount of the hardware and the extent of the picture are small.