A thought about easilly implementing left-side driving

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  • #18482
    electricmonk2k
    Participant

    Here’s an idea I had for how the devs could implement left-side driving with little effort. All geometry in the scene could be mirrored horizontally. This could be done by flipping the x-co-ordinate either when projecting the scene from camera-space to screen-space, or when transforming from world-space to camera-space.

    Of course, any textures with writing on them would have to be mirrored too, and the mouse co-ordinates would also have to be mirrored when picking geometry in the scene. Also, if back-face culling is used by the renderer, this might also be affected by mirroring the scene. As the overlay is composed after the transformation of the 3D-part of the view, the rendering of the overlay does not need to be changed. Is there anything else that needs to be taken into account here?

    One aspect of this particular implementation of left-side driving is that the player can switch between right-side driving and left-side driving mid-game, but then, the world will be mirrored.

    This still does not solve the problem of those oddball countries such as France and Belgium where road-vehicles drive on the right, and trains drive on the left. For that, you would have to implement driving-side at the track-level and not at the world-to-screen-transformation-level.

     

    #18493
    simonmd
    Participant

    What about trams and buses, would they be reversed as well? Otherwise, the doors would be on the wrong side.

    #18498
    electricmonk2k
    Participant

    The idea behind mirroring either the transformation or projection is that all geometry in the 3D world will be mirrored. This includes track, vehicles and their doors, and unfortunately also textures (this is only a problem if the textures have writing on them).

    IMaybe it could be possible to add plug-in camera functionality. As well as making a mirroring-camera, you’d be able to do some funky effects like fish-eye lenses as well.

    #18499
    simonmd
    Participant

    A thought that occurs to me is that since the USA DLC it’s possible to set a theme to a game, so there is no reason that a ‘UK DLC’ would not work, reversed track, roads and specialised UK vehicles for road use.

    However, as it seems the Devs have long since given up on this game, its very unlikely.

    #18521
    electricmonk2k
    Participant

    All that’s needed to create a  new theme is to replace the models and textures etc. I haven’t looked into the mods much, but I’d be surprised if there wasn’t a good selection of UK rolling-stock created by the community by now.

    However, as it seems the Devs have long since given up on this game, its very unlikely.

    Actually, according to their post in this thread, which post-dates the release of the last patch, they refer to “the next patch”, which implies they’re working on another patch (or at least started working on one).

    • This reply was modified 5 years, 8 months ago by electricmonk2k. Reason: Made link work
    #18528
    Norfolk_Chris
    Participant

    I suggested the mirroring idea to CO for CIM2.  They immediately rejected the idea out of hand as impractical.

    Perhaps they felt there was insufficient demand for LHD, or more likely the were working on CSL and had no further interest in developing CIM2.

    I still think that this is a workable idea and hope that Urban Games will give it serious consideration.

    All visual content can be mirrored, except of course any text.  That may be the most difficult part as it will also affect fan produced content that is not controlled by Urban Games.  Only buildings and road vehicles would be affected as trains are not handed in the game (they can use platforms on either side), and will thus not need any modification.

    • This reply was modified 5 years, 8 months ago by Norfolk_Chris.
    #18545
    electricmonk2k
    Participant

    I’ve not played CIM, CIM2 or CSL. Did left-sided driving get implemented in CSL?

    Apart from text-reversal, another potential problem is that back-faced culling might be affected. To solve this, either the direction of the vertices in the polygons needs to be reversed, the test for the Z-component of the polygon-normals needs to be reversed, or the X-component in screen-space needs to be reversed after the back-facing polygons have been culled.

    As for text being the wrong way round, I’m not sure how easy it would be to automatically reverse texture-co-ordinates on models (is doing this automatically even feasible). The only idea I had is that LHS-country-themed vehicles and buildings would have mirrored text and RHS-country-themed vehicles and buildings would have unmirrored text. Of course this would create problems for anyone wanting to mix text-containing vehicles and buildings from LHS-countries and RHS-countries, although one advantage mirroring does have is that the doors on busses would be on the correct side regardless of where the bus was from.

    I’ve not tried this myself, but I think you can get trains to drive LHS by placing the signals between the two tracks instead of on the edge (it works but signals in the middle instead of the sides does not look so nice). Also, making the trains run LHS using this method might confuse the pathfinder (although I’m not sure about that).

     

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