There are some sources a computer can get its images from. It goes similar to this...

Source:
1: Simply using a digital camera. (Real World or simply Photography)
2: Generating with computers ... (CG or Computer Graphics)
* 3D polygons/triangles. (Maya, Cinema4D)
* Voxels, they are 3D Pixel.
* 2D polygons/triangles. Or vector graphics. (PhotoShop, Paint.Net)
* Using a graphic tabled for "drawing". I think those are raster graphics. (PhotoShop, Paint.Net)

Now of course, those two sources can be blended. Here an example:

1: A tiger and a landscape, could be completely generated with computers.
2: A tiger and a landscape, could be a pure real world photo.
3: The tiger could be computer generated, put on real world landscape photo. T'is a blend!

Actually at this point, a filter could be nice. So that one can decide whether he/she wants a real world photo or something computer generated, or a mix of both.

Sorry, for making thing complicated again, but you know I try to stay scientific as much as I can.

... anyways, that filter could of course also filter Booby Girls and Pointless Violence ...