Structure of The Roman Surface
The Roman surface has four bulbous "lobes", each one on a different corner of a tetrahedron.
A Roman surface can be constructed by splicing together three hyperbolic paraboloids and then smoothing out the edges as necessary so that it will fit a desired shape (e.g. parametrization).
Let there be these three hyperbolic paraboloids:
- x = yz,
- y = zx,
- z = xy.
These three hyperbolic paraboloids intersect externally along the six edges of a tetrahedron and internally along the three axes. The internal intersections are loci of double points. The three loci of double points: x = 0, y = 0, and z = 0, intersect at a triple point at the origin.
For example, given x = yz and y = zx, the second paraboloid is equivalent to x = y/z. Then
and either y = 0 or z2 = 1 so that z = ±1. Their two external intersections are
- x = y, z = 1;
- x = −y, z = −1.
Likewise, the other external intersections are
- x = z, y = 1;
- x = −z, y = −1;
- y = z, x = 1;
- y = −z, x = −1.
Let us see the pieces being put together. Join the paraboloids y = xz and x = yz. The result is shown in Figure 1.
|
The paraboloid y = x z is shown in blue and orange. The paraboloid x = y z is shown in cyan and purple. In the image the paraboloids are seen to intersect along the z = 0 axis. If the paraboloids are extended, they should also be seen to intersect along the lines
- z = 1, y = x;
- z = −1, y = −x.
The two paraboloids together look like a pair of orchids joined back-to-back.
Now run the third hyperbolic paraboloid, z = xy, through them. The result is shown in Figure 2.
|
On the west-southwest and east-northeast directions in Figure 2 there are a pair of openings. These openings are lobes and need to be closed up. When the openings are closed up, the result is the Roman surface shown in Figure 3.
|
A pair of lobes can be seen in the West and East directions of Figure 3. Another pair of lobes are hidden underneath the third (z = xy) paraboloid and lie in the North and South directions.
If the three intersecting hyperbolic paraboloids are drawn far enough that they intersect along the edges of a tetrahedron, then the result is as shown in Figure 4.
|
One of the lobes is seen frontally—head on—in Figure 4. The lobe can be seen to be one of the four corners of the tetrahedron.
If the continuous surface in Figure 4 has its sharp edges rounded out—smoothed out—then the result is the Roman surface in Figure 5.
|
One of the lobes of the Roman surface is seen frontally in Figure 5, and its bulbous – balloon-like—shape is evident.
If the surface in Figure 5 is turned around 180 degrees and then turned upside down, the result is as shown in Figure 6.
|
Figure 6 shows three lobes seen sideways. Between each pair of lobes there is a locus of double points corresponding to a coordinate axis. The three loci intersect at a triple point at the origin. The fourth lobe is hidden and points in the direction directly opposite from the viewer. The Roman surface shown at the top of this article also has three lobes in sideways view.
Read more about this topic: Roman Surface
Famous quotes containing the words structure of, structure, roman and/or surface:
“Im a Sunday School teacher, and Ive always known that the structure of law is founded on the Christian ethic that you shall love the Lord your God and your neighbor as yourselfa very high and perfect standard. We all know the fallibility of man, and the contentions in society, as described by Reinhold Niebuhr and many others, dont permit us to achieve perfection.”
—Jimmy Carter (James Earl Carter, Jr.)
“... the structure of a page of good prose is, analyzed logically, not something frozen but the vibrating of a bridge, which changes with every step one takes on it.”
—Robert Musil (18801942)
“I do not believe in the creed professed by the Jewish Church, by the Roman Church, by the Greek Church, by the Turkish Church, by the Protestant Church, nor by any church that I know of. My own mind is my own church.”
—Thomas Paine (17371809)
“I cannot but conclude the bulk of your natives to be the most pernicious race of little, odious vermin that Nature ever suffered to crawl upon the surface of the earth.”
—Jonathan Swift (16671745)