TITLE: Architectual Glass Blocks
NAME: Alan Langford
COUNTRY: Canada
EMAIL: jal@cybertouch.com
WEBPAGE: http://www.cybertouch.com/~jal but it's under serious reconstruction...

TOPIC: Glass
COPYRIGHT: I SUBMIT TO THE STANDARD RAYTRACING COMPETITION COPYRIGHT.
JPGFILE: 3blkjal.jpg
ZIPFILE: 3blkjal.zip
RENDERER USED: PovRay 3.00
TOOLS USED: Paint Shop Pro
RENDER TIME: 5 days 13 hours 17 minutes 46 seconds at 1024x768 antiailiased
HARDWARE USED: Pentium 120, 512Kb cache, 16Mb RAM
IMAGE DESCRIPTION: 
Three architectural glass blocks floating on the ubiquitous checker
background. This was a test image for the glass block object. 

DESCRIPTION OF HOW THIS IMAGE WAS CREATED: 
One of the scenes I want to render features a wall of glass blocks. This is a
test scene used to build the block objects. The current competition topic was a
coincidence, so I decided to release this as is. Besides, the render times are
so slow that I would never be able to dress this scene up and make the
submission deadline. Each block consists of two half-blocks that have been
"cemented" together. Although this scene only features a distorted block, the
distortion is an add-on to a flat see-through window type block.

My first attempt at these objects tried to assemble each half-block from a set
of smaller boxes, but PovRay hit max trace depth too soon and rendered large
areas of the blocks as black. Since the render times are already punitive, I
reconstructed them starting with a single box of glass, then used CSG operators
to remove the areas around the outside and in the core. This left fewer
internal surfaces and allows a render with the default trace level. If these
were intended to be stand-alone objects, I would have spent more time ensuring
that various corners and edges are more rounded, as are the real ones. In
pratice, they will be used in walls of glass that have the blocks surrounded by
mortar, so that level of detail is not useful.

The glass texture is much brighter than the standard ones provided by PovRay. I
found that the existing textures all left the scene too dark after the light
had gone through so many surfaces. The glass in this image simply transmits 97
of available light.

The distortions inside the block are constructed from a blob of several
cylinders that have been skewed relative to each other, plus one that cuts
across at a diagonal. The blob object gets truncated by a box that is the same
size as the inside of the core of the flat glass block. This leaves a square
lens that gets placed it inside the core.

Most test renders of the elements of this scene were done with "pigment {Red}"
replacing the glass in order to reduce rendering times. Once I was looking at
details of the glass itself, I used "+SP4 +EP4" to get a quicker look at the
scene in lower resolution before deciding to tie my sysem up for a week on a
full render.

This image was rendered at 1024x768, then scaled to 800x600 and output as JPEG.
The conversion to JPEG causes serious loss of detail around the edges of the
blocks.

Total elapsed time from concept to this image was about 3 weeks of sporadic work
on evening and weekends, plus nearly 6 days of solid fretting about possible
power failures, system bugs, etc. :)