Quote from: chippwalters on May 31, 2009, 09:12:33 PM
Vue is very different w/regard to GI vs Radiosity. You can see an example here. I believe Radiosity is a superset of GI. In anycase, I don't know how TG interprets either.
Hi Chipp,
Vue and Terragen use the term "global illumination" to mean different things, so it's not always obvious how to compare them directly. In Vue, "Global Radiosity" is a more realistic solution than "Global Illumination", but that's just a Vue thing. It may be an unfortunate side effetc of their introducing their better global illumination (which they called radiosity) after they had already released a simpler solution called global illumination (I may be wrong about the reasons though). In Terragen, Global Illumination is analogous to Vue's Global Radiosity (as I understand it). Global Illumination in Terragen tries to account for diffuse interreflections, specular interreflections (with limited quality), as well as light from luminous/glowing/emitting surfaces and atmosphere and clouds. Also, the clouds and atmosphere react to global illumination just like surfaces do (I think Spectral Atmospheres 2 has this now too).
So when we say Global Illumination in Terragen we're talking about a solution that tries to account for *any* kind of secondary light in the scene. No exceptions (unless you count inaccuracies or level-of-detail simplifications). In Vue, I think this happens with their "Global Radiosity", but they are using the term 'radiosity' incorrectly. In CG research, 'radiosity' is an old algorithm which was developed a long time ago to simulate
diffuse interreflections only. Global Illumination is a more general term for all lighting contributions which are not coming from direct light sources (to put it informally). So Radiosity is a
subset of Global Illumination in the wider CG community. In Vue it's just become a bit confused because of the terminology.
http://en.wikipedia.org/wiki/Radiosity_(3D_computer_graphics)http://en.wikipedia.org/wiki/Global_illuminationThe radiosity article i linked to above is not to describe how Vue does it, because I believe Vue uses a Monte Carlo solution which is (or can be) more general than radiosity.
Matt