[layer8]

The difference is that applying textures to a 3D object is almost never a pixel-perfect operation, in the sense of texture pixels mapping 1:1 to final screen pixels, whereas for text rendering that’s exactly what you want. Either those are different APIs, or you have to take extra care to ensure the 1:1 mapping is achieved.

[adastra22]

There are ways to configure the texture blitter to be precisely 1:1. This is written into the GL/Vulkan standards for exactly this reason, and all hardware supports/special cases it. It is how pretty much every GUI subsystem out there handles windowing.

[layer8]

Yes, my point is that this is a special case separate from normal 3D graphics.

[incrudible]

…so why are GPUs not the way to do this, when GPUs are in fact the way it is commonly done?

[jlokier]

The transforms are specified so you can position things perfectly these days, when aligned with screen pixels.

Think of the compositing of layers of translucent windows used in modern 2d window managers, while dragging them around. Or even scrolling in a browser. Those rely on the GPU for fast compositing.

Even for 3d, think of the screen-space techniques used in games, where it's necessary to draw a scene in layers combined with each other in various interesting logical ways (for shadows, lighting, surface texture, etc), with the pixels of each layer matching up in a reliable way.