Data tiles can be combined to form attribute data sets for use in generating computer graphics images. Tiles may be arranged in a regular grid pattern or in arbitrary, irregular positions. Tiles can be overlapped slightly and blended to hide tile boundaries. The value of the combined data set in an overlap region may be a weighted sum of values from the tiles. To compensate for reduced variance and contrast caused by blending, the values in overlap regions can be scaled by a variance correction factor. The variance correction factor is the inverse of the reduction in variance from the source tiles. Tile values can be scaled by their weights and variance correction values at the time they are combined or in advance, if the pattern of tile overlaps are consistent. Data tiles can be comprised of bandlimited noise data or other data types.