iigs-game-engine/src

= Rendering Pipeline =

The engine run through the following render loop on every frame

1. Lock in any changes to the play field scroll position
2. Erase/Redraw dirty sprites into the sprite plane
   • If a sprite has moved a different amount than the scroll position, it's marked dirty
   • If a sprite was just added on this frame, it's marked dirty
   • Any sprite that overlaps a dirty sprite is marked as impacted
   • All dirty sprites are erased from the sprite plane
   • All dirty and impacted sprites are drawn into the sprite plane
   • All of the play field tiles that intersect dirty sprites are marked as dirty with the sprite flag set
3. If a scroll map is defined
   • Calculate the new regions of the screen that have been scrolled into view
   • For each new tile
     • Copy the tile descriptor from the tile map into the tile store
     • Mark the tile as dirty
4. For each dirty tile
   • Load the tile descriptor from the tile store
   • Dispatch to the appropriate tile renderer
   • Clear the tile dirty flag
5. If any Masked Overlays are defined
   • Turn off shadowing
   • Draw the play field on the Overlay rows
   • Turn on shadowing
6. In top-to-bottom order
   • Draw any Maksed Overlays
   • Draw any Opaque Overlays
   • Draw any play field rows

NOTES

• The dirty tile list has a fast test to see if a tile has already been marked as dirty it is not added twice
• The tile renderer is where data from the sprite plane is combined with tile data to show the sprites on-screen.
• Typically, there will not be Overlays defined and the last step of the renderer is just a single render of all playfield lines at once.