Modeling and mapping a good looking intersection was quite tricky for me in the beginning because it has some challenges:

  • mesh (so the mapping) must follow car trails (red lines in the picture below)
    2016-08-03_145133 2016-08-03_1451332
    finished model
    2016-08-04_154417 2016-08-04_154459
  • we need to use as small texture as possible (ideally the same as for the normal road)
  • we need to avoid any visible seems in texture mapping

My approach that seems to work well 🙂

It is quite easy and quick even there is still a need of some manual correction (merging vertices, remapping).

  1. I start with creating a road elements for each trail (with mapped seamless texture) – if we are modelling the intersection from the screenshot above, there are 3 trails = we need 3 road elements for each

    Example of such element (for an intersection below)
  2. Use Grease Pencil to highlight the intersection shape, trails, road symbols etc, it will serve you as a guide in the actual modelling – in most cases an orthophoto maps are quite low quality
  3. Create bezier curves and shape them along the trails / lines you want the mapping to follow
    Tip for Blender: always use Top Ortho view (NumPad 7 and toggle NumPad 5 between Ortho / Perspective) – this way you are sure you place new points on the ground (with Z=0)
    It is much easier and more accurate to work with a flat roads and make an elevation later.
  4. For each element, add these modifiers:
    • Array (Fit Curve -> select corresponding curve) and
    • Curve (again, select the curve to follow)The result should look like this:
      If the road element doesn’t follow the curve properly, make sure it is not rotated (apply transformations using Ctrl+A) and it’s position corresponds the position of the curve
  5. Now because the elements are overlaying each other, we need to cut them and delete polygons that are overlaying – these are some methods how to do that:
    • separating & extruding edges of the most visually important element and cut other elements by them (with Knife Project tool – again, don’t forget to be in Top Ortho view!)
    • cut all the elements with Knife tool manually using MultiEdit addon
    • create a custom cutting element (bezier curve converted to mesh for example), extrude and execute Knife Project for each element with it

    Example – extruded edge of the main road which is going to be used as a cutting element, in picture #2 you can see road elements have been cut and remaining polygons deleted:
    2016-06-09_014827 2016-06-09_022313

  6. In this stage we need to merge close vertices (use Remove Doubles and set some larger distance – but always check it doesn’t make any unwanted merges!), triangulate newly created polygons (and then use Tris to Quads), fill all empty areas with new polygons and map them to the texture to fit surrounded polygons so the seam is nearly invisible.
    Tip for Blender: In the right panel (“N” shortcut) use “Only Render” checkbox to temporary hide the wireframe overlay to check the mapping result.
    Also use “Mesh Display” menu for disabling Faces / Edges highlight when editing UV for the same reason.
  7. The intersection is done!
    Then you can of course start adding all those little details, subdivide it where necessary etc. 🙂