Is it ALWAYS better to use Vray Lights?

[Marshall_Craft]

Hi, I keep searching for the right thread, but I can't seem to locate the help I need. My office works a lot on health care facilities where we have long corridors branching off of central spaces and many ceiling lights. Is it always faster to use Vray Lights in these cases or should I be using standard lights? Thanks for any help.


- Alex

[Morbid Angel]

not at all, infact its known that vray lights in large numbers tend to slow things down, because naturally they are all area lights thus require samples to compute shadows and luminance. If you can get away with spot/directional/omni do so.

[Marshall_Craft]

Thanks! The tutorials and help files suggest that it's faster, but not relative to standard lights. But I SHOULD be using Vray mats, right? I know not to use Architectural (sorry, VIZ user here,) but I thought i've read that Vray users prefer Vray mats for speed.

-Alex

[Morbid Angel]

indeed, vray mats are preferable. Consider that light cache doesnt work with max mats for one. Others is speed as you say. But it doesnt hurt to have standart mat here and there

[Giovanni]

indeed, vray mats are preferable. Consider that light cache doesnt work with max mats for one. Others is speed as you say. But it doesnt hurt to have standart mat here and there

LC dos not work with standard mats?

What U mean?



gio

[Morbid Angel]

perhaps my info is old, but last time I read up on it, it was specificly said that at this time lc works only with vray mats.
Maybe this has changed now...vlado would know

[powerandrubber]

I think LC works with std mats but photons do not. The help file should say for sure.

[tom schuelke]

Hi Morbid Angel ,

you are wrong...


Lc works allready from times when it was called lightmap... together with standart materials. so your info is realy very very old


no problem with standart materials, but of course, vr materials are by far better...

[andrewjohn81]

LC and photons work with standard mats, but not correctly is all.

You'll get different results, but it's not always "bad"

Thats all.

It's just best to use vray mats to get consistant results.

[Wilyman]

Going back to the original question, there's quite an interesting piece in the tutorials section at www.treddi.com, about using planes with VRayLightMtl in place of VRay Lights.

It seems that using one plane with a VRayLightMtl applied will produce a slower render time than a VRay Light of similar size and intensity, but as you add more and more lights to a scene, using VRayLightMtls will actually start to make the render times quicker and quicker in comparison to using VRay Lights.

Unfortunately the article is in Italian, but I found babelfish.altavista.com did a reasonable enough job of translating it.

Hopefully, this link will work:

http://babelfish.altavista.com/babel...wtopic%3D15315

If not, the original Italian page can be found here:

http://www.treddi.com/forum/index.php?showtopic=15315

It seems like it might be a useful technique to use in situations like this, where a lot of ceiling lights are required.

Cheers,

John

[Marshall_Craft]

there was a time when i could possibly translate it myself (but i doubt i know any Italian CG terms.) thanks for the link.


- Alex

[studioDIM]

I've quite skipped through the article, but aside from using textured lights, it seems to forget that Vray lights can be "baked" in the IRMap solution via a checkbox (i'm a native italian language speaker).
In fact the article compares standard AreaLight raytracing with IRMap tracing of area lightsources.

So, unless you use textured light (gradients and imagemaps), you can get good speeds (probably the same as VrayLight materials) if you use standard Vray Arealights by checking "Store with irradiance Map".
Also you'll have the same kind of issues with them as you'd have with VRayLight materials (blurriness of the shadows) in computing a sharpish shadow, which might be alleviated by raising the IRMap settings a bit.

Complex colouring was also probably one of the two reasons why the VrayLightMTL was built in the first place (the second might be topology, not straightforward speed, imo).

All i can say is that i used 30 VrayLights in a render with the IRMap setting turned on with good results, in terms of speed and quality, in an airport's corridor render (some were very long arealights...).

Lele