vray dome light

[vlado]

You can use the dome light with GI quite successfully.

Usually, most of the fine shadow details in exterior scenes come from the skylight, while GI effects are a lot smoother.

When you use the irradiance map to represent the skylight, you need high settings to get good detail and even so, this may take a lot of time.

With the dome light, you leave the details to the light, while the irradiance map only has to take care of the more smooth secondary illumination. In this way, you can get a better-looking image in less time.

The real advantage of the dome light will be obvious when you can use a HDR image to map it - in this case, it will produce much cleaner results that GI, because it will put more samples in the brighter parts of the map, instead of doing uniform sampling.

Best regards,
Vlado

[tammo]

i do moving object animations most of the time and use domelight (without GI) in all projects.

its fast and flicker-free.
easy to setup with only a single quality setting.
it never surprises you with artifacts after a night of rendering.

i use GI only in interiors with bounced light.

[flipside]

Sorry rerender but testing with such settings is not really fair.

Here are my tests:




Imo, using dome light with store with ir map is useless, because that is exactly what normal skylight is... That is also 'stored' with the ir map. In the dome light you have to set the subdivs, even when using store=ON. So you need to control ir map hsph AND dome light subdivs = more work. Plus it renders longer. You also loose the advantage of the raytraced shadows.

Dome lights can be usefull in situations where the GI takes ages to render because you need fine GI detail. In that case, using a domelight can help alot. Instead of using ir map with skylight to compute shadows, now the domelight creates these. The first bounce will then be computed with ir map (this first bounce was the second bounce when using skylight!).

A good use imo would be a dome light with store=off, and first bounce IR map, and dimmed second bounces. This would be very similar to a normal skylight rendering with first and secondary GI, but with very fine (fake) GI detail coming from the dome light area shadows. Because the main part of lighting is already taken care of by the dome light, you don't need very high ir map settings (like you usually don't use very high secondoray bounce settings when using skylight+irmap+qmc).

like this:
skylight(1.0)+irmap(1.0)+qmcGI(0.8 )



Dome light(1.0)+irmap(1.0)+qmcGI(0.35)


Rendertimes are of course much higher, but if you would want this detail with only skylight, you would need very high GI settings, resulting in even higher rendertimes.


edit: seems I was making my post while vlado already replied...

[instinct]

@cpnichols :

Ambient Occlusion works basically like this :

From the point of the geometry you are processing you are shooting rays in random directions (within a defined cone). When you hit any other geometry within a defined range in one ray the point is darkened. if a lot of rays hit other geometry it´s further darken till it gets black in extreme cases. The result is NOT identical with GI or Domelight rendering..AND you got Total control over the distribution of shadowed parts as you can define a min and max radius, bias etc. Another big advantage is that you dont have to trace 128 shadowed lights, but it´s rather similar to a glossy reflection (computation wise).

Refer to this thread : as we had a long discussion about why not to confuse true AO with GI or Domelight rendering :

http://www.chaosgroup.com/forum/phpB...ient+occlusion

Dieter also posted a comparison of an AO pass and a GI pass on our b-class interior renderings.

Greetings,
Thorsten

[priad]

The real advantage of the dome light will be obvious when you can use a HDR image to map it - in this case, it will produce much cleaner results that GI, because it will put more samples in the brighter parts of the map, instead of doing uniform sampling.

Can you explain how put a HDR in the dome light?
Or it's just an hdr in the environment or reflexion slot?

regards

[TishoChaos]

Currently, you can't.

[priad]

ok

[RErender]

Wouter, what irradiance map settings were you using? obviously as the imap settings are higher the dome light is less relevent and even becomes a burden as in your tests. The dome light has been successful in our real world exterior scenes in reducing artifacts with little time hit, believe it or not

[cpnichols]

@cpnichols :

Ambient Occlusion works basically like this :

From the point of the geometry you are processing you are shooting rays in random directions (within a defined cone). When you hit any other geometry within a defined range in one ray the point is darkened. if a lot of rays hit other geometry it´s further darken till it gets black in extreme cases. The result is NOT identical with GI or Domelight rendering..AND you got Total control over the distribution of shadowed parts as you can define a min and max radius, bias etc. Another big advantage is that you dont have to trace 128 shadowed lights, but it´s rather similar to a glossy reflection (computation wise).

Refer to this thread : as we had a long discussion about why not to confuse true AO with GI or Domelight rendering :

http://www.chaosgroup.com/forum/phpB...ient+occlusion

Dieter also posted a comparison of an AO pass and a GI pass on our b-class interior renderings.

Greetings,
Thorsten

I am very clear about what Ambient Occlusion is, having been a lead lighter at Digital Domain and having worked on and with ambient occlusion shaders on some major feature films such as I, Robot and Day After Tomorrow and others. I think you are confusing method with definition. A shadow is a method of occlusion, and until the method that you are describing was invented, was the only way to do Ambient Occlusion. No the results are not the same because the method is different. BTW Dieter shader is a pretty cool shader, but not a true Ambient Occlusion shader by definition, as the geometry of the interior of the car would occlude the seats, rendering them black. Those type of shaders, while very similar in principle to the AO shader, are actually refered to as "dirt" shaders. Nonetheless, they can be made to get a similar "effect" of what people have come to think of as Ambient Occlusion.

[analogueWay]

I feel like a small fish in a big pond compared with some of the guys and girls in these forums. I-Robot was beautiful, as was the B-Class animation.

So, if the dome light gives us what is basically ambient occlusion, then would the requests for ambient occlusion - that were made after everyone saw the B-Class animation - be better classified as requests for a dirt shader (similar to frDirt - available for a GI renderer of a different name)?

I am glad that so many people are weighing in with answers and ideas. It is sounding like the dome light with lower GI settings is an answer to lower frame times and/or higher quality for exterior animations.

-Jeremy

[instinct]

I would definately say it is ambient occlusion, but be it AO or a dirtshader it is VERY different from GI or a domelight and that was the point i was making...as a maximum radius should be part of every AO shader, and when set small enough the roof isnt taken into account, hence the occlusion is ignored on purpose...and that´s what´s so great about as you dont get shadows all over in interior shots. And not having a max radius would mean the renderer would have to trace every ray to the scene-bounding box wich wouldnt be really efficient, no ?

Thorsten

[Da_elf]

i find usually the most straight forward definition of the name should be the only definition. ambient occlution should thus be the occlusion of ambient light. not a dirt map. and certainly not something thats fairly much used on indoor scenes unless most of the lighting indoors comes from external ambeint light from large windows.

[cpnichols]

Thank you Da_elf for making my point... the moment you add a radius, you are no longer dealing with a AO shader.

[RErender]

I hereby declare all said and as of yet unfathomed in this presupposed genre to be just "occlusion shaders" plain and simple! :P

[percydaman]

i wanna dirt shader...