A computer graphics rendering apparatus according to an embodiment of the present invention generates a screen image, using plural texture images having different mipmap levels. The apparatus generates a normalized texture coordinate of a texture image, generates, from the normalized texture coordinate of the texture image, a texel coordinate of a texel in the texture image, according to a mipmap level of the texture image, and generates, regarding an image block in the texture image, an index value indicating a cache line corresponding to the image block, using a texel coordinate of a texel in the image block. The apparatus generates the index value such that index values of image blocks in the same position are different, between two texture images having mipmap levels adjacent to each other.