Quick Status

14 March 1999

I redid all the color statements to use a gamma of 1.0 instead of 2.2. The granite doesn't look the same and I don't care for the large yellow splotches. And I have too much light. But otherwise, the operation was a success. Reciently I aquired a copy of Leveller, and plan to use that to work on the Outside ground.

Later... Adjusted light sources' intensities to match original image.

8 March 1999

Mick sent an updated Poser file (refined pose of the statue). I finally succeeded in converting this to a POV mesh.

7 March 1999

Work on the Sig Block: I spent a couple hours getting nowhere, trying the text sideways on the edge. Finally decided to keep it this direction, but two lines.

Meanwhile, looked at programs to read DXF files, with less than spectacular success. Still have not received Leveller.

6 March 1999

Made the text carved directly into the structure rather than on an inset block. Upped the ambiant light inside the cutouts. It took 2 hours 34 minutes to render — why? It normally takes just under 2 hours.

3 March 1999

A furst cut [PI] of the signature block. Made the blue sky a little less saturated, just to get an idea.

2 March 1999

Feedback indicated that the chain's randomness, though not unseen in a chain, looked awkeard in this case because the well-formed round links would readily straighten out. I denormalized the distribution a little (more deviation from 90 degrees) but further restricted the range (no links are totally turned flat to each other).

1 March 1999

The simple chain links were well received, but the random twisting of the chain was though by some to be unrealistic. As it turns out, a rough "normal" distribution is rather easy to do after all, so I changed the chain to use a normal distribution centered at 90 degrees for each link.

28 February 1999

Wrote the "chain link" macro that is used by the chain macro. This is a simple torus link with random orientation (each link rests at a uniformly distributed angle between 20 through 140 degrees on the previous link).

Also added some distress to the teapot, but no patena yet. Does it need anything?

I've not done the mounting brackets on the teapot nor the eyelets where the chain hangs from. I don't know if it will be necessary in the final scene, as the details are too small. Intermediate idea is to offset the last link by half a phase, so the half-link sticking into the teapot looks like an eye, but don't bother with a different shape or modeling the soldering.

Why Teapots?

The Utah Teapot has a history in Computer Graphics. It appears in many many articles as the archtypical test data. Steve Baker has posted The History Of The Teapot, and there are a few other web pages on the subject as well.

A Teapot bicubic patch shape actually comes with POV, and I adapted this include file, making it more macro-friendly but not changing the actual data. It appears to have a bottom, so is not "pure".

27 February 1999

I got the hanging teapot implemented as a macro that automatically figures out where the chains connect to both the teapot shape and the support. This uses the trace() function in the POV Superpatch, and this looks like a great feature for this issue in general. However, the first cut at the macro was too limited, as I had to deal with the varying gravity. Now it works, and I can flesh out the details without worrying about the logic framework around it deciding where things go.

In this day's render, one teapot is upside down.

25 February 1999

A first cut at some "chains" to hang the teapot with. I started out with spheres for the links as a first approximation, and it actually looks pretty good.

24 February 1999

I fixed up the geometry of the main structure, and got rid of the "step up" on some of the pillars. There is still a measurement problem I don't understand, since it ought to fit perfectly, but I worked around it.

I also added a little roughness to the stone, and tried the new marble texture on the columns as well as the statue. I've had a number of comments saying that the marble looks good now, so I'm through with that, at least for the time being.

23 February 1999

Over the last couple of days, I decided that a good marbled texture just doesn't show discontinuities well, to show that a structure is made of individual blocks of stone. What did look good is adding beveled edges to the blocks, showing as V-shaped grooves. This is done in addition to making the textures discontiguous, for realism.

I also experimented at length with textures for the statue. The chain of inspiration was (1) The Arrighini Sculptures website, which shows some photos of marble statues, and mentions "white Carrara statuary marble"; (2) A web search for "Carrara" led me to the Materials page of the Furrer marble company of Carrara. I used the "Bianco Carrara C" illustration as my model for the texture, shown below.

I loaded to photo into Photoshop and zoomed in 600% to see the pixels, and sampled them to get a true palette of color. Plain layers didn't work, and I ended up needing two layers, the base layer a lusterous blue, and a top layer contributing the darker streaks, which are of a different pattern than the color mixing that forms the luster. Finally, I adjusted the ambiant and diffuse lighting characteristics to "expose" the sample properly without whiting-out the highlights. Roughening up the surface seems to help, too.

Rendered Texture
Photograph
#local Bianco_Carrara_C_2 =
   texture {     // underlying
      pigment {
         gradient x
         color_map {
            [0.00   rgb<226/256, 214/256, 218/256> ]  // color A
            [0.50   rgb<226/256, 213/256. 223/256> ]  // color B
            [1.00   rgb<226/256, 214/256, 218/256> ]  // smoothly back to A
            }
         turbulence 0.3
         }
      finish {
         ambient 0.14
         diffuse 0.48
         }
      normal {  bumps 0.1 scale 0.1 }
      }
   texture {   // dusky layer
      pigment {
         spotted
         color_map {
            [0.0   rgbt<218/256 ,201/256, 207/256, 0.1>  ]
            [1.0   White transmit 1 ]
            }
         scale <0.1,1,1>
         scale 2
         }
      finish {
         ambient 0.14
         diffuse 0.48
         }
      }

20 February 1999

First of all, the archways are now a macro, and it's not quite lined up right. I'll get back to the geometry later; the point is now I can design a complex archway and it will appear in each place, at the proper size and scale. I've been experimenting with how it should look.

Most of the stone (granite and marble) textures are chaotic enough that the seams between individual blocks don't show, which means creating them is a waste. I finally hit on the more stratified stone (T_Stone21 in the POV distrubution) that will show a subtle but resolvable discontinuity without having to put in a sharp edge. But, I don't know if I like it.

I also made the main structure a more serious stone texture, mainly just to see how it looks.

I gave the Teapot a highly reflective brass finish. It reflects the other elements in the scene, which is both classic ray-trace imagary as well as very Escheresque. I don't know how how the reflection if the bizzare world will stand up (since it's meant to view from a specific angle) 'till I get a full render out (it's tracing as I type up these notes).

later...

The brass teapot is too highly reflective -- it might as well be mirror silver.

I don't like the different color for the archways. I think I'll try another approach.

18 February 1999

Tried a simple height field for the outside ground, just to gain a feel for height fields. Also put in a fancier sky, just to see (it's a stock sky from skies.inc). Changed the lighting model to see if it makes a difference (it does -- much more realistic shadows)

17 February 1999

I put the sculpture and the hanging teapot in place. Again, they are both drafts. The sculpture needs some posing and more precice positioning. The teapot needs proper suspensions and supports detail, as well as final textures. This is just "blocked out" to get all the elements in place before doing the fine work. I decided to do all the rough work first, rather than do one thing at a time all the way, because elements will interact with each other and the presence of one thing might effect how I finish another. Or, I may change something and all the fine work would be for waste.

16 February 1999

OK, whatever muscle I use for trigonometry is really going to be sore in the morning after this workout! I made a sketch of an "Outside" object, and got three different views (of the same object) through the archways. Everything automatically lines up with the building's definitions—there is only one fudge number in the whole thing.

Note that this is indeed completely done with Constructive Solid Geometry. It is not pasted together from multiple pictures, or imagemaps during rendering.

15 February 1999

Mick Hazelgrove was kind enough to send me a statue model after reading my question on the 13th.

I ported Nathan O'Brien's Corinthian column to a POV 3.1 #macro featuring full control over the height and width. Specify the total height and it creates a proper length shank without distorting the top and bottom pieces. Specify the desired radius and it sizes the top and bottom pieces to match. It also uses a dynamic scoped #local to control the texture and fluting mode, rather than requiring the editing of the include files.

Reading the c.g.r.r. newsgroup, I saw a thread on the Utah Teapot. It struck me that this is exactly what I need for "something hanging in the archways ... that's an homage to computer art" in my notes from the 13th.

14 February 1999

I looked into Leveller for doing the background, and looked into Poser for doing a statue.

I downloaded Nathan O'Brien's Classical Orders of Architecture Columns .INC file, added a sprinkling of semicolons, and played around with it. It took just a few test renders to figure out where his origin is located, and easily scaled it to fit based on the documented size. It will need a little work to scale properly, though—I need to adjust the length of the main shank without affecting the base and capitol. His code seems straightforward, so I think I'll just recode it as a macro that takes a length, and while I'm at it, make it easier to specify textures.

The normal sized render doesn't show the detail on the column to good advantage. The fluting just looks like a mess. Test renders as twice the size indicate that it does trace properly, so in the final poster size it's just what I want—lots of detail on a small scale. I may change the fluting a little to look better in the image (after all, this is a fantasy image, so why let architectural accuracy get in the way of a good image? Escher cheats in that his lines, when projected, don't line up as they should. Being a hand drawing, he shows what he wants you to see instead of having to arrange things in 3D so that they do in fact look that way).

Initial posting, 13 February 1999

I'm working on a POV model inspired by Escher's Another World. This is intended to become a large print to hang over my fireplace.

So far, I have a roughed out model of the central structure. This was rather confusing to do, to put it mildly. It's all done directly with POV source and a little doodling on the side. To get a closer look at joints and other details, I use close-up cameras. The confusion stems from the lack of a definite "up" and the self-similarness throughout, so it's easy to get lost.

The print I'm using for inspiration can be seen at the World of Escher. This is called Another World II, so I'm calling mine Another World 3.0. Escher's work is actually 3 woodcuts which must be used to make an actual print. Likewise, mine is a computer bitmap which must be printed. Even fifty years ago, Escher had the same confusion we do today about the lack of an "original" as with a painting.

I plan to try a "grid" stonework texture as seen in Escher's woodcut.

The view through the archways in Escher's woodcut are a stylized cratered ground, looking like a moonscape. This is one of the features that attracted me to doing a remake in this media, as a classic fractal generated landscape will be an interesting counterpart.

Instead of the strange bird, I'm thinking of using a stone statue (perhaps a Greek style reclining nude?). It will be visible in all three views, so I need a real 3-D model of some detail. Any pointers to where I can find data?

Escher also has horn shape hanging from chains, which helps establish a sence of gravity in each sub-view. So it's probably important to the illusiion to have something hanging in the archways, but I have not decided what. Something that's an homage to computer art would be ideal.

Any comments and advice appreciated.


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