You may recognize the "character" model from the xna 3d starter tutorial, I haven't gotten very far yet so I'm just using it as a placeholder for now. The game is pretty much 2D, but uses a 3D model for the character, rectangles are used for collision since the terrain is all sprites (I honestly have no idea if a model with oriented bounding boxes can collide with rectangle-based terrain at all, but I digress). I'm new to cameras and 3D in general so matrices and whatnot is still quite confusing, so I've pretty much copy-pasted the camera and model-drawing code for now, and not surprisingly they're giving me some trouble. Drawing the character model at any other Z-coordinate than 0 makes it overly complicated to make the hitbox rectangles stick to the character, so I'd prefer to draw it at 0 if at all possible, however, the current copy-pasted camera isn't exactly agreeable. This is the camera code.

cameraProjectionMatrix = Matrix.CreatePerspectiveFieldOfView(

MathHelper.ToRadians(45.0f),

graphics.GraphicsDevice.Viewport.AspectRatio,

1.0f,

10000.0f);

The 45° float gives me trouble because the further the character goes away from the middle of the screen, the more angled the character (in this case a ufo, as mentioned earlier) becomes. (Example 1, Example 2). Changing the 45° float to 1° fixes this issue, but forces me to scale the model to a ridiculously low scale (about 0.0001f, if I recall correctly) and also makes the model look quite bad, as the resolution of it is pretty low.As you can see on the screenshots, there's a little box in the upper left corner, that's my rectangle hitbox. As you can also see, it is unfortunately nowhere near the model itself. The main reason for this is (again, I may or may not be right, as I'm pretty new to 3D) that the position of the rectangle is an integer while the position of the model is a Vector3 (that is, floats).This is how the position of the hitbox is decided...

It looks like you want an orthographic view, not a perspective view.  Use the Matrix.CeateOthographic instead of Matrix.CreatePerspectiveFieldOfView (look it up on msdn).   The object will always be the same size regardless of it's distance to the camera.

Thanks a lot, this solved the angled model issue perfectly! :) I'm afraid I have some new problems though. The model treats the middle of the screen as 0 for both the X and Y coordinates, while the hitbox uses actual screen coordinates, treating the upper left corner as 0,0, is there any way I can make the model follow the same coordinate system as the rectangle does? Also, for some reason, the hitbox moves up if the model moves down and vice versa, I really have no idea why it does that.

Your hitbox is in a different coordinate system than your model.   Your hitboxes are in screen space, while your model is in world space.   I would suggest transforming your object into screen space as I'm guessing that's where most of the 2d stuff is in.

I followed the link that I mentioned above and managed to integrate it into my code, so I've partially got things working now, the hitbox moves nicely and the model is at the same coordinates as the hitbox (according to Console.WriteLine(Character.position.ToString());, anyway). Unfortunately the model isn't visible, so something's still wrong for sure.

Just because your model has the same position as the hitbox doesn't mean that they are the same relative position to the camera.  Your model is going through some world space and camera space transformations before it get's rendered the screen.   Your sprites do not go through the same transformations because they are already in "2D" screen space.   That's why you can't assume that the same position mean's the same position in screen space.

After a few days of work I've got things working pretty well, the model lines up with the hitbox and follows it perfectly, and I'm currently working on the physics. Collision worked fine until recently, for some (to me) unexplicable reason there's a box that won't collide with my hitbox at all, except for the first instance of aforementioned box. This box is the one that shows up as the number 6 on the grid. There's also another thing, you can jump against the 5-block and then jump again without touching the ground, which is unintended. This doesn't work with the normal walls, so it is probably related the upper side of the 5-block, and possibly to the fact that the corners of all the blocks are empty and doesn't have rectangles. I'm not really sure how to solve the corner thing, so if have any idea, I'd love to hear it, thanks in advance.