# Multiple Grids

The ocean file below differs from the previous example in that it now has one auxiliary surface (the line `number_aux_oceans` `1` and the seven after). The primary surface here now has a resolution of 0.035m (3.5 cm), which is much higher than the 1m resolution of the previous example. The surface from the previous example now becomes an auxiliary surface in this one. The resulting surface has all of same large bumps and troughs as in the preceding example, but has a much higher level of detail.

  `RenderWorld_data_file ocean 5 5`
  `n_points_x` `1024` `1`
  `n_points_y` `1024` `1`
  `dx` `0.035`
  `dy` `0.035`
  `spectrum_file` `spec2.dat`
  `generate_file` `yes`
  `random_seed` `91405`
  `end`
  `number_aux_oceans` `1`
  `n_points_x` `512`
  `n_points_y` `512`
  `dx` `1`
  `dy` `1`
  `spectrum_file` `spec1.dat`
  `generate_file` `yes`
  `random_seed` `1451`
  `end`
  `number_disturbances` `0`
  `box_depth 20.`
  `reference_time` `0`
  `surface_type` `round`
  `radius` `6371230`
  `max_distance` `100`
  `double_distance` `60`
  `wind_type fixed`
  `wind_direction` `90`
  `wind_velocity` `8`
  `waves yes`
  `water_type` `3`
  `external_exact` `no`
  `glitter` `no`
  `whitecaps` `no`
  `textures` `no`
  `sunbeams` `no`
  `exclude_items no`
  `number_of_bands 3`
  `band_ids 1 2 3`
  `index_of_refraction` `1.34 1.34 1.34`
  `end`

Two points to note: First, the primary grid must be the high resolution grid. Reversing the roles of the two grids in this example will not produce the desired results. Second, for the high resolution grid, the lines specifying the number of grid points needs to have a "1" at the end of the line. The auxiliary grids must not have this additional entry. Beyond that, the specification format for the auxiliary grids is identical to that of the main grid.

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