gen_gr3_input.py

from pyschism.mesh.hgrid import Gr3

def write_gr3_file(filename, grd, value, description):
    with open(filename, 'w') as f:
        f.write(f"{description}\n")
        f.write(f"{grd.triangles.shape[0]} {grd.values.shape[0]}\n")
        for i in range(grd.values.shape[0]):
            x, y = grd.coords[i]
            if isinstance(value, float):
                value_str = f"{value:.6e}"
            else:
                value_str = str(value)
            
            # Format each value with desired spacing
            formatted_id = f"{i + 1}"
            formatted_x = f"{x:.6f}"
            formatted_y = f"{y:.6f}"
            formatted_value = value_str.replace('e-0', 'e-')  # Remove leading zero in exponent
            
            # Ensure exactly 5 spaces between ID and X coordinate
            id_field = formatted_id.ljust(len(formatted_id) + 5)
            
            # Write the formatted line to the file with correct spacing
            f.write(f"{id_field}{formatted_x}{' ' * 6}{formatted_y} {formatted_value}\n")
        
        for i in range(grd.triangles.shape[0]):
            elem = grd.triangles[i]
            f.write(f"{i+1} 3 {elem[0]+1} {elem[1]+1} {elem[2]+1}\n")

if __name__ == '__main__':
    hgrid = Gr3.open('../../data/hgrid.gr3', crs='epsg:4326')
    grd = hgrid.copy()
    gr3_names = ['albedo', 'diffmax', 'diffmin', 'watertype', 'windrot_geo2proj','manning']
    values = [2.000000e-1, 1.0, 1e-6, 4, 0.00000000, 2.5000000e-02]
    for name, value in zip(gr3_names, values):
        write_gr3_file(f'{name}.gr3', grd, value, name)