Describes: applications of Metameshing, Edge Tension, metameshing in U and V.
We have already seen how Metameshing can turn a coarse polygonal spaceship into a smoothly beveled one. It does so refining the polygonal surface until it approximates a spline surface.
Start Tornado3D or open a new project. Add a cube, select it and Copy/ Paste it three times so that there are four identical cubes in the workspace.
Now leave untouched the first one, select the second and Metamesh it with 0.25 as U Edge Tension. V Edge Tension will be automatically set to 0.75. Repeat the Metameshing for the other two cubes, using 0.5 (V is set to 0.5) and 0.75 (V is set to 0.25).
Counterclockwise from top left: original cube, Metameshing with 0.25 / 0.75, 0.5/0.5 and 0.75 / 0.25
Observe the result. When seen in order of increasing U Edge Tension and decreasing V Edge Tension, the meshed cubes appear to collapse, having their corners progressively cut out to approximate a rounder shape.
Now repeat the Metameshings, using the same values as before. In theory two Metameshing applications are required to correctly add detail to an object. In practice, there is no firm rule apart from how the object looks.
Reapplying the same Metamesh parameters to the same objects makes them rounder
Metamesh's corner cutting proceeds and especially the cube Metameshed with identical U and V values (0.5, 0.5 -halfway in both directions) begins to approach a spherical shape. The other two instead preserve some of the cube's nature either externally (the second one) or internally (the last one).
This refinement process can be repeated as much as needed taking care of not surpassing the 32000 points, edges or faces maximum value. Metameshing adds a lot of detail so it's easy to overrun an object's maximums.
Now delete the cubes and with Objects> Polygonal> Pyramid add two pyramids placing them side by side. Preview them in Photorealistic mode, they will both show Phong artifacts and appear inflated. This is normal, since their faces meet sharply and yet Phong interpolation tries to render them smoothly. Usually an object like a pyramid or a cube should be rendered as flat shaded to avoid this.
Select the rightmost pyramid and apply to it a Metameshing with U Edge set to 0.05 (this will set V Edge Tension to 0.95). Now the Metameshed Pyramid has thin beveled corners that act as halfway surfaces for Phong interpolation and gets rendered correctly in Phong shad ing. This also adds to the resulting image's quality since real world objects do not have edges as sharp as those that 3D graphics can render. For example, building a room out of a cube would be a perfect example of an object that benefits from a thin bevel at the corners.
The original pyramid (left) has shading problems evidentiated by dark and bright areas near its edges; Metameshing solves them adding a thin bevel (right)