Function elevationMapNormalsToRGBA
elevationMapNormalsToRGBA(    data: Float32Array,    columns: number,    xScale: number,    yScale: number,    rotation?: number,    nullValue?: number,): Uint8Array<ArrayBuffer> Parameters
- data: Float32Array
 - columns: number
 - xScale: number
 - yScale: number
 - rotation: number = 0
 - nullValue: number = -1
 
Returns Uint8Array<ArrayBuffer>
Calcukate and encode surface normals from an elevation grid as RGBA image values.