A background (sky box) in a video game or other virtual reality environment dynamically changes as a function of a parameter, producing a more realistic display. Luminance-only texture and color texture data are employed to create the background. The color texture data are provided as a lookup table in which one axis of the lookup table corresponds to time or another variable, and the other axis indicates the colors of pixels in the display as a function of the altitude or azimuth of the pixels. The luminance-only texture data are thus modulated by the chrominance values from the color texture data for pixels in the background. Optionally, one of a plurality of two-dimensional color textures can be selected as a function of the variable and applied to the luminance-only texture data.