radiosity in vray?

[evilryu530]

can we control the radiosity in vray? make light more natural?

[dalomar_cg]

radiosity in vray?

Vray doesn't do radiosity because it uses Global Illumination to do its light calculation. Its much more realistiic then Radiosity, and much less of a pain to deal with.

[evilryu530]

radiosity in vray?

please explain what you mean.....

[dtr]

radiosity in vray?

Damien

Right on about radiosity, but in one
of the demo presets I thought I saw
a photon mapping option.

In Jeremy Birn's book 'Digital Light and Rendering'
this was considered a type or radiosity.

Please get my mind right on this ?? EH!

Dave

[dalomar_cg]

radiosity in vray?

Fundamentally Global Illumination and Radiosity use different light transport algorithims. Basically meaning that the way vray calculates light is different then a radiosity calculation.

One of the main issues with Radiosity is that there is an actual mesh that is created for the model, and each face contains the illumination data. This becomes an issue for two reasons. First is the creation of the mesh itself. Its can be quite an intense process as well as adding allot of information to the file equalling huge files. The second issue which is related to the first, is that illumination is stored or calculated per face. This means that one face only has a certain range of illumination values. This means that in order to have a very accurate solution (even though it would never be physically accurate) it requires a very dense mesh. This causes more time, more file size, and the great thing is that if you move one object or change one light you get to do it all over again.

GI does all its calculations on the fly. Meaning the you don't need to do any precalculations (you can, but thats special).

As for Photon mapping, Vray is unique in that it has several different methods for calculating illumination. Your right dtr, photomapping can be use in combination with radiosity, and uses some of the principles of it. Most users don't actually use photon mapping to do any light calculations (Primary or secondary bounces I mean)with Vray. However Vray does use photon mapping to create caustics. This actually means that you can save your caustics solution much like you would save a radiosity solution.

One of the main reasons why Vray users don't use photomapping is that Light Cache is a very similar method, but is much more simple to set up. With photonmapping you have to set up the subdivisions on a per light basis. The calcuation is done by actually tracing rays, based on those subdivisions, from the light to wherever it bounces around in the scene. Light Cache uses the same principle, but with two important differences. First off it doesn't use individual light subdivisions, but rather a global subdivisions that is based on the image itself. Secondly it traces rays from the camera as opposed to from the light. These two things allow for LC to be what is know as a view specific calculation method. This means that for each rendering only the information for what is in view is calculated. This is quicker and the solution can be saved as well.

Hope this clarifies a bit about Radiosity, GI, and Photon mapping

[evilryu530]

radiosity in vray?

ah! i see now. what about when you use GI and you want to make your shadows soft? right now in sketchup, the shadows are hard edged and when i render it it is also hard edged. is there other presets that will make the edges soft? thank you.

[dalomar_cg]

radiosity in vray?

I believe that is coming from the Vray sun. Off the top of my head I can't think of a way to make it have softer shadows (this computer doesn't have vfsu or su for that matter). With Rectangular lights the softness of the shadow is related to the size of the light itself.
Small light=sharper shadows big light=softer shadows

[evilryu530]

radiosity in vray?

question about the retangular lights, i just got beta 3 and im not sure how to use it...can you explain?

[joe_b]

radiosity in vray?

See my response in your other post

[dtr]

radiosity in vray?

Damien

Wow! and thanks for the concise and informative
treatise on the way Vray works for light.

Also a good sales point as speed is a must
have for the SU types and good to know just
how V works to achieve a faster render.

Dave

[joe_b]

radiosity in vray?

Yeah - now I just need to get our scene-parsing where it needs to be. That seems to take longer than the render in large scenes....

[dtr]

radiosity in vray?

Joe

FYI I ran a memcheck util and after the Malibu P file sent
to you crashes the system still holds the memory and does not
release same. about 50%

Sys = Win 2K sp4

When SU is rebooted and V run again the mem drops again to 24%

Hope this is some clue and help to y'all.

Off for a ski trip to Mammoth Calif, so
out of the loop till next week.

Bye for now

Dave