1. An image processing method comprising: optically obtaining a plurality of first images by photographing an object to be rendered from a plurality of different directions, and optically obtaining second images that pertain to distance information of the object to be rendered; generating a geometrical shape model of the object to be rendered on the basis of the second images using a plurality of voxels; generating a plurality of microfacets as two dimensional elements that are each centered inside a voxel in a manner to approximate a three-dimensional shape of the geometrical shape model, wherein the width of each microfacet is calculated as equal to, or greater than, the square root of three times the width of each corresponding voxel; executing a billboarding process that rotates the plurality of microfacets to keep the plurality of microfacets substantially vertical to a view direction; and generating a third image by selecting texture images for respective microfacets from the plurality of first images on the basis of the plurality of photographing directions and the view direction, and by projecting the selected texture images onto the microfacets.