working artists


Mark Stock
(click on thumbnail to view larger version)

artist's statement | technical statement | process

technical statement

The algorithm used to create the subject in Mesh #3 Iso is called a vortex method. The rotations that make up a turbulent flow can be described by a collection of small vortex elements, represented in this method by short segments. Each vortex element influences air near it to rotate around it. The summation of the effects of all of these vortex elements creates a complicated flowfield that we recognized as turbulence. The computer simulation marches forward in time, updating the position of the mesh at regular time intervals. The mesh of vortex lines is periodically written to a file in the form of a long list of cylinder descriptions.

Test renders were made of several interesting-looking "frames" in this time sequence. The frame that worked best was one that exhibited enough wall interaction while retaining some remnant of the initial symmetry. An isometric view was chosen to reveal the sharp boundaries of the virtual box enclosing the flow.
The scene in Refinery 53 was far simpler to design, though more attention to detail was required during the piece's execution. Custom software was written to fill a Cartesian grid space with continuous and non-overlapping pipe segments. Parameters to the program were varied and output visualized until a scene with sufficient visual density was created. The cylindrical viewpoint and high resolution warranted a detailed and time-consuming pseudo-radiosity calculation in the rendering stage.

All of my rendering is done with Radiance because it incorporates a lighting model that can calculate the effect of light interreflection throughout the scene quickly and accurately. This, more than clever light placement or excessive texture mapping, allows an image to instill a sense of realism.

Once the scene has been described, Radiance compiles it into an octree, which is then used to speed up intersection tests in the raytracing routine. During rendering, results from the interreflection calculation are cached in a separate file. This aids in view selection by reducing the turnaround time for preview renders.

Programs included with Radiance were used to downsample the final rendered image and reduce the intrinsic high-dynamic-range image for print.