Yes, there are memory problems however, nothing to do with yable, but a blender python problem.
I have seen the term “GI” used here a lot. What exactly is it and can somone give me a reference that explains it in simple non techical terms.
GI is an acronym for “Global Illumination” which yafray actually does not do, not full GI anyway. It tends to be misunderstood for anything from very soft shadows, to skylight to radiosity. But these are all just aspects of it. Global Illumination means just that, rendering calculations that involve light where ever it originates from.
So say you are rendering a room scene with a window, a lamp on the ceiling, a table and a glass on that table. Now lets say that the renderer is currently looking at a point on the table close to the glass. To calculate Global Illumination for that point, you have to consider all the light arriving at that point wherever it comes from, so for this particular scene that would be the lamp on the ceiling, the light coming from outside through the window, the light originating from the lamp on the ceiling and the light from outside coming through the window bouncing of the walls onto the table, the light refracted/reflected by the glass of the lamp on the ceiling and the light from outside coming through the window, the light bouncing of the walls refracted/reflected by the glass and so on and so on… It is an infinite process.
Yafray uses two methods to calculate approximations of GI, one is photonmapping, which can calculate things like ‘caustics’ which is light directly refracted/reflected by other objects, as well as the indirect light, ‘diffuse’ light bouncing of objects with other materials.
Then there is the pathlight, which does a limited form of so-called ‘pathtracing’, it only considers indirect light of basic colored materials (diffuse colors). So yafray doesn’t do full Global Illumination.
In fact, very few renderers do, there is lot more types of light interaction that is still ignored by a lot of renderers, simple because there is not always a practical method yet to do this efficiently.
One recent addition to the GI spectrum is so-called ‘subsurface scattering’ which calculates what happens with light that travels through semi-transparent(translucent) materials, which is known for a long time of course, but only recently methods have been developped to calculate these efficiently (even in realtime now). Not in yafray yet however.
Anway, the methods in yafray, both have advantages and disadvantages, the photonlight can calculate very fast indirect lighting and caustics but is fairly difficult to setup, parameters are not very intuitive, nothing to do with yafray, other renderers (like POV too) have that same problem as well.
Then there is the pathlight, which can be very noisy depending on the scene, fully visible skylight is very fast, but the same light shining through a tiny window in a room will cause lots of noise and grain if you don’t turn up the samples, and in turn can really add up in rendertime.
Another method people confuse with GI is the hemilight, however, this just calculates shadows, nothing more, but it is also faster if you want a ‘GI’ look.
POVray however can do these things too, but uses an approximation that nevertheless has the potential to create much smoother pictures a lot faster without much difference in different situations.
Don’t forget though that POV has had a history of well over a decade of development and can’t be compared in any way to yafray yet.
I would certainly give jms’ povanim a try, he also has been working on that for a very long time and it shows.
So in the end it all comes down to whatever you like best and/or find easier to use.
Don’t forget Blender itself however…
