Tilemaps

[avahe-kellenberger]

Implement tilemaps.

• Render tiles to a buffer, then render the buffer (1 draw call per frame instead of O(N))
• 2D Buffer array, for cases where tilemaps span large areas
• Update cells that change, but don't need to re-render the whole buffer

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We may want to try integrating with Tiled.

Could possibly generate code as a compilation step rather that reading in a file at runtime.