How can I use a Texture2D larger than 2048 x 2048?

I'm having issues working with a large image. I've read other threads on using images larger than a Texture2D supports, but found nothing that addresses my problem specifically with implementation hints.

My screen resolution is 1920 x 1080. I'm working in C# XNA. The game in question is pretty much a board game.

I have an 3840 x 3840 image I planned to use for the terrain map. The idea was to make each new game look a little different from the last by having the program randomly select a 1920 x 1080 segment of that large image to display. My code to randomly select and display a part of the image is working.

Unfortunately, I can't even get the initial 3840 x 3840 image to load. Just picking "Add Existing Item" and adding the image to the content window on the right causes my program to error that a Texture2D can only be 2048 x 2048 maximum.

How do I best handle this? I may later need to scale or rotate the map.

Suggestions I've seen around:

• Cut it up into sections.
• Use a smaller image that is made "seamless" or "tile-able", then choose a random starting X,Y point in it and fill the screen with that.

Are these good ways to go about it? How would I actually do this? Would I still be able to scale and rotate the map?

• – Andrew Russell Mar 19 '14 at 2:33

I would not use the content pipeline for this image. Instead I would load the image into a buffer using your choice of image loader (eg: System.Drawing.Bitmap). Then create a Texture2D of the desired final size and use SetData to fill it with the desired pixel data. Then unload the original image.

There are two major reasons for doing this. First of all, it gets around the maximum texture size issue - as per your question. Secondly, it allows you to store your very large image in a format like jpeg or png, which will have a much smaller file size than an xnb.

If you find yourself needing more than a small, fixed area of this image (for example, if you rotate, you might have to have a larger area of the map loaded in), then you can still use the above technique to slice up your image into small enough chunks at runtime and render it as multiple "tiles".

Scaling and rotating the map (at runtime) is as simple as doing the appropriate maths and passing the correct parameters to SpriteBatch.Draw. Alternately, you could pass an appropriate tranformation matrix to SpriteBatch.Begin. (The best choice is generally the one that requires the least code.)

(You could use render target if you wanted to "bake" this transformation into a texture. Remember to handle "device lost", or bounce it back to a regular texture with SetData. It doesn't really gain you anything when rotating, and very little when scaling. I wouldn't bother.)

Alternately, you could change your game to use the HiDef profile, where the maximum texture size is 4096 x 4096. (Set this in the properties for your project.) Obviously this only works if your map image is not going to get any bigger than that.