Feature: spline update tool

[AlonzoTG]

Game now forces spline updates but does a horrible job with maps that have any significant quantity of old splines. Need this tool to do a much more reasonable job of conversion.

[scottanderson]

This is a good idea for a feature, but the details need to be fleshed out before it can be implemented:

1. Converting splines from the old (multi-segment) spline system to the new (single-segment) objects results in many short spline sections, which causes dramatically worse performance than what a manual rebuild would produce. It is necessary to write an algorithm that can merge two adjacent spline segments which can be closely approximated with a single longer spline segment.

2. There is no direct mapping of spline types in the old system to the new system. It is possible that groundwork and bridge splines could be discarded, and the floating rail tracks could be converted to the new system.

// Types for old splines:
export enum SplineType {
    rail = 0,
    variable_grade = 1,
    constant_grade = 2,
    wooden_bridge = 3,
    rail_deck = 4,
    variable_stone_wall = 5,
    constant_stone_wall = 6,
    steel_bridge = 7,
    steel_truss = 8,
}

// Types for new splines:
export enum SplineTrackType {
    BALLAST_H01 = 'ballast_h01',
    BALLAST_H05 = 'ballast_h05',
    BALLAST_H10 = 'ballast_h10',
    RAIL_914 = 'rail_914',
    RAIL_914_BRIDGE_TRUSS = 'rail_914_bridge_truss',
    RAIL_914_BUMPER = 'rail_914_bumper',
    RAIL_914_H01 = 'rail_914_h01',
    RAIL_914_H05 = 'rail_914_h05',
    RAIL_914_H10 = 'rail_914_h10',
    RAIL_914_SWITCH_3WAY_LEFT = 'rail_914_switch_3way_left',
    RAIL_914_SWITCH_3WAY_LEFT_NOBALLAST = 'rail_914_switch_3way_left_noballast',
    RAIL_914_SWITCH_3WAY_RIGHT = 'rail_914_switch_3way_right',
    RAIL_914_SWITCH_3WAY_RIGHT_NOBALLAST = 'rail_914_switch_3way_right_noballast',
    RAIL_914_SWITCH_CROSS_45 = 'rail_914_switch_cross_45',
    RAIL_914_SWITCH_CROSS_90 = 'rail_914_switch_cross_90',
    RAIL_914_SWITCH_LEFT = 'rail_914_switch_left',
    RAIL_914_SWITCH_LEFT_MIRROR = 'rail_914_switch_left_mirror',
    RAIL_914_SWITCH_LEFT_MIRROR_NOBALLAST = 'rail_914_switch_left_mirror_noballast',
    RAIL_914_SWITCH_LEFT_NOBALLAST = 'rail_914_switch_left_noballast',
    RAIL_914_SWITCH_RIGHT = 'rail_914_switch_right',
    RAIL_914_SWITCH_RIGHT_MIRROR = 'rail_914_switch_right_mirror',
    RAIL_914_SWITCH_RIGHT_MIRROR_NOBALLAST = 'rail_914_switch_right_mirror_noballast',
    RAIL_914_SWITCH_RIGHT_NOBALLAST = 'rail_914_switch_right_noballast',
    RAIL_914_TRESTLE_PILE_01 = 'rail_914_trestle_pile_01',
    RAIL_914_TRESTLE_STEEL_01 = 'rail_914_trestle_steel_01',
    RAIL_914_TRESTLE_WOOD_01 = 'rail_914_trestle_wood_01',
    RAIL_914_TUNNEL = 'rail_914_tunnel',
    RAIL_914_WALL_01 = 'rail_914_wall_01',
    RAIL_914_WALL_01_NORAIL = 'rail_914_wall_01_norail',
}

[scottanderson]

For converting spline coordinates from the old system to the new system, catmullRomToHermite() already exists in the code. It is used as an adapter to get the new spline grade and curvature annotations working with old splines, but it could also be used as part of a spline upgrade tool.