Implement instancing / batch rendering techniques to speed up map rendering

[ultraq]

As expected, drawing each map tile and element with its own draw call is very slow 😅 Luckily, a few ideas for how to go about solving this exist, and the ones I'll need to look into include:

• generating a large texture for map tiles and referencing them as offsets into the tile map instead of the usual bottom-left-to-top-right texture coordinates
• batching all of the vertex data together so that it can be operated on with a single draw call
• share the same mesh data for each of the tiles (they're all 24x24 pixel sprites!) so that I can then use the instancing draw calls, glDrawArraysInstanced/glDrawElementsInstanced, on them

Resources:

• https://learnopengl.com/Advanced-OpenGL/Instancing
• https://www.youtube.com/watch?v=5df3NvQNzUs

[ultraq]

Got a batch renderer working without too many restrictions on it now, so pretty happy with that. I don't know how to fit in instancing just yet as I don't really have many instances of the same thing (though every map tile could be an instance of the same 24x24 mesh with different texture coordinates and transforms for positions 🤔). I think the batch renderer will do for now - when I start having to create many of the same units/structures, particularly with different palette shifts, I might look into instancing again.