subject: Would You Be Able to Tell a Computer-made 3d Drawing from a Real Photograph? [print this page] Would You Be Able to Tell a Computer-made 3d Drawing from a Real Photograph?
You've seen those neat 3d wallpapers everyone has these days: the scenery and everything in it has a perfect molten metal look, thatlooks good enough to eat. Of course they don't jump out of the screen like in those old movies that required a pair of special glasses; 3d drawings, the kind computers make these days, are remarkable for a different reason: they are perfectly shaped, with perfect lighting, reflection, perspective and texture. For this qualities they feel as real and three-dimensional as a real photograph. How exactly is this effect achieved though?
Those old black-and-white, or should we say black and sepia Mickey Mouse cartoons when they first appeared seemed three-dimensional compared to the stick figure felix the Cat animations people were used to looking at before. Until Fantasia appeared; then those breathtaking color images seemed pretty much three-dimensional as compared to the monochrome Mickey Mouse that came before. Do you see a trend here? The more real-world details a drawing is endowed with, the more your brain is willing to feel that it is being shown the real thing - until it grows used to it. The more the computing power available rises today, the more real-world details an animator is able to bring in. What kind of details might trick our modern jaded eyes the best way then today?
A soccer ball is a great way to understand how a computer makes 3d drawings. If you have ever seen one, they make those balls sewing together the 32 individual five- and six-sided polygons (pentagons and hexagons) of leather into a perfect sphere. A polygon is a basic unit of the computer graphics engine in any computer. When you want a shape, any kind, the computer figures out how to draw one out of an arrangement of an assortment of triangles and polygons, just the way a soccer ball is made out of 32 polygonal panels. Once a skeleton made of polygons is in place, the computer needs to figure out a number of other things: what kind of surface the skeleton is to have, hard and shiny or soft and dull; the surface needs to be reflecting light a certain way, and its color is to shine or dull out depending on where the light is shining from.
A real object doesn't really need to think about how each visible quality turns out: it just is the way it is. And the way it is just happens to be incredibly varied and complex. The shape itself has such a fine texture of infinite depth; it reflects and absorbs light in a hundred ways. Even a simple rock is not a uniform material all over. This then, is one of the best ways to make a 3-D drawing look real: to patiently give it as many different textures all over, and make them reflect light in different realistic ways.
Students at any computer graphics school often like to take a challenge where they paint in a 3d drawing into a real photograph, say, a computer-drawn hat on the head of a man in a photograph, only to pass their handiwork around and ask people to find out if the hat is real or artificial. You would be surprised how many people get it wrong.
