3D Animation Workshop: Lesson 17: Photorealism 101 | 2
Lesson 17 - Photorealism 101 - Part 2
The best place to start is with a careful examination of the final product. The 3-D artist must be able to learn from the finished work of others, because it will be rare for someone to bring you through the development process (as we will do here). In fact, this scene was developed originally as an attempt to learn from a particularly supurb photorealistic scene set in a chemistry lab. Only the glass beaker filled with a colored solution remains from this inspiration, which ultimately evolved into a kitchen still-life in morning light.
Here is the final render again.
The scene has been very carefully planned to test a wide range of different material surfaces. The apples must have a particular blend of diffuse colors, and must have a distinctive glossiness. The lemon has only a single diffuse color, but is defined by its texture and by its SPECULAR REFLECTION. The spoon is a silver metallic surface, which is an extremely important effect to master for general 3-D work. And the beaker! The beaker is the star of the scene--and justifiably so. Glass objects are hard enough, but we've put a transparent liquid inside.
Let's look more carefully at the beaker for a moment. Do you see how the sense of glass is created? The surface itself is perfectly transparent, so why do we see it--or rather, what do we see? We see, among other things, the effect of refraction through the glass. The checked pattern on the wallpaper is critical in this respect. We compare the pattern as seen directly with the pattern as seen through the glass, and the distortion is immediately interpreted as the effect of refraction through a curved, transparent surface. Notice also the difference between the effect as viewed through both sides of the beaker and the effect, at the top, where we see only through the back side of the beaker. These small differences, of which the general viewer is typically unconscious, make all the difference is selling the idea of "glass."
3-D artists are always talking about "selling" an object or effect. This usage may seem a little crass when speaking of what is undoubtedly art, but the 3-D artist is always thinking about what it takes to convince the viewer of the reality of a rendered scene. Little things make all the difference. Standing 15 feet away from a portrait in a museum, we see a touch of warm sunlight caress the subject's nose. At 2 feet, we realize that the "sunlight" is a blob of yellow paint peaked with brush marks. The skilled painter understands those cues that the viewer will instantly interpret as reality. The 3-D artist must learn the same. In the case of the glass beaker, the refraction sells the object, and where the refraction is less obvious due to the background, the effect is weakened.
Compare the identical scene with the checkerboard pattern removed from the surface of the wall.
Notice how the front edge of the glass seems to disappear, and the back edge also to a lesser degree. There has been no change in the lighting, or in the surfacing of the beaker. The edge is less visible simply because it no longer serves as a boundary between two refraction patterns. The pattern also creates the sense that there is a real wall at a defined distance behind the objects, and not just a vague background. Notice why this is so. The regular checked pattern displays a perspective distortion--the little squares get smaller as they move away from the viewer toward the right of the image. This gives the viewer a strong sense of receding space, and is precisely the device used by many of the of early Renaissance painters when the use of perspective was new and exciting. Art history students will remember the conventional checkerboard pattern used on floors in these breakthrough paintings to create a sense of depth.
And then there's the shadows.
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Created: August 19, 1997
Revised: August 19, 1997