GitLab

Problem

• Right now, the 2D visualization of the maps and vehicles uses the Graphics2D java class inside the Swing components.
• This is not a very efficient rendering method, especially for large scale cities.
• It is also not precise: the polygon geometry can only be passed with integer pixel positions.

Solution

Use OpenGL rendering.

• As OpenGL library (for example): JOGL
  • JOGL in Swing (Still up-to-date ?)
  • OpenGL 4 JOGL sample
• TODOs:
  • Test a simple 2D triangle with a basic shader.
  • Make it build and run using the JOGL maven artifacts.
  • Make a colored triangle shader with an orthogonal view matrix, test binding it to the map controls (position, zoom). Render a simple triangle (or 2)
  • Make a colored line shader, same view matrix, test a simple outline.
  • Generate the building geometry in one VBO/VAO/EBO set.
    • Use the already split convex parts
    • The convex polygon parts can be rendered using the GL_TRIANGLE_FAN drawing mode
    • In combination with the Primitive Restart
      • Use an Element-Buffer
      • Use the PRIMITIVE_RESTART index to separate triangle fans for different polygons
      • Since we only want to draw contiguous vertices, the glMultiDrawElements() method can be useful
  • Generate the road geometry (or visualization lines)
  • Generate the vehicle geometry (one VBO/EBO/VAO set)
    • Same triangle shader, but give it a view+model matrix (pre-multiplied)
  • All the debug lines/elements (AABB, building outlines, ...) can be in their own VBO/EBO/VAO.
• Check the thread interaction between Swing and OpenGL. The OpenGL calls are not thread-safe for a given context. Be sure that the OpenGL calls happen in the correct thread.
  • Swing Threads

Note: The existing visualization already "pre-generates" the geometry in some way to save computation. Changing to save this geometry in OpenGL buffer would not be a big change.