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Upper left, the "true" max value of the grid was used and so the gradient was mapped in the most accurate, or predictable way. Upper right, the gradient is repeated several times. Lower left, since the max value used is double compared to what is actually stored in the grid, only half of the gradient is mapped to it. Lower right, tiling was off, and the reflectance 0 color was white - the gradient is only mapped to parts of the grid whose range is 0.0 - 0.2, and in parts with higher ranges, the reflectance 0 color becomes visible.