Basically, they make a 3d mesh and stick it in front of a camera.
Those that do pixel perfect stuff but change size in different resolutions do so by carefully positioning the meshes so that the center of each texel falls in the center of a pixel.
And that's basically it. You can use sprites, or use meshes... I use meshes in my system because it allows me to use a single mesh with a single texture to position many different letters on the screen at once. Most systems probablt use meshes and not sprites because of this. You don't want hundreds of sprites onscreen at once because each sprite has one surface and surfaces slow your game down a lot. You can't have more than around 200-400 surfaces in view at one time and maintain a good framerate.
Those that do pixel perfect stuff but change size in different resolutions do so by carefully positioning the meshes so that the center of each texel falls in the center of a pixel.
And that's basically it. You can use sprites, or use meshes... I use meshes in my system because it allows me to use a single mesh with a single texture to position many different letters on the screen at once. Most systems probablt use meshes and not sprites because of this. You don't want hundreds of sprites onscreen at once because each sprite has one surface and surfaces slow your game down a lot. You can't have more than around 200-400 surfaces in view at one time and maintain a good framerate.