Date: Sun, 7 Dec 1997 03:12:59 +0400 From: Charles Blaquiere Subject: Re: [IML] quest: chat about rays LOPOLO wrote: > > Id like ask if someone knows how namy rays is Imagine counting for 640x512 > picture for example. Is it same number like pixels of picture? Greetings to the Czech Republic! Here is the way I understand Imagine's ray tracing. I believe Imagine initially traces one light ray per pixel, backwards from the camera as you know. Whenever the ray hits an object face that is partially reflective, the ray splits into two rays, one that bounces off the object and one that continues along the original path. Each of these rays could then hit other objects that may cause more rays to be computed. This means more than one ray per pixel could be computed, depending on your objects. However, Imagine can also launch more than one initial ray per pixel; this is done when anti-aliasing. Pixels that vary from their neighbors by more than X brightness levels, where X is the value of the "threshold" slider (from 0 to 255), will be selected by Imagine for anti-aliasing. For those pixels, Imagine will trace more than one initial ray per pixel, sending multiple rays in slightly different directions, to cover sub-areas of the pixel that would be missed if only one ray were traced. The number of additional initial rays is controlled by the "ray limit", from 0 (left edge of the slider) to 255. This means that, for pixels where anti-aliasing must be performed, Imagine will start with 1 to 256 rays. Supposing there are no reflective objects in the scene, in a 640x512 render containing 327,680 pixels, Imagine could trace between 327,680 and 83,886,080 rays. Is this the answer you were looking for?