VRay HDRI dilemma

[Stephen Thomas]

Is there any benefit in creating a VRay dome light with HDRI mapped to the image based lighting slot, over simply using the skylight environment override slot?

[Ricardo Eloy]

Besides not having to go to the rendering dialog everytime you want to change its intensity, using a dome gives you the oportunity to change the look of the lighting simply rotating the dome. It also produces photons (so you can have caustics!) and work with photon map (haven't used the last one recently, but I assume it works).

[Stephen Thomas]

OK Rick, thanks for the help.

 

Stef

[DavidR]

Besides not having to go to the rendering dialog everytime you want to change its intensity, using a dome gives you the oportunity to change the look of the lighting simply rotating the dome. It also produces photons (so you can have caustics!) and work with photon map (haven't used the last one recently, but I assume it works).

?!? You can change the intensity in the mat editor, and you can rotate it in the mat editor too. Our testing has shown faster, cleaner rendering by putting it in the environment slot, but you need to check that it doesn;t revert to 'screen' -it should normally be spherical, but crashes can make it flip back to screen, making renderings very blotchy. Haven't tried photon map.

[Christopher Nichols]

The biggest advantage of the Domelight is the way it adaptively shoots rays, allowing for sharp shadows from an HDR. It is in fact way superior than any other IBL system, and as far as I know, no single rendering engine can produce the quality/time of the domelight IBL system that vray has. By a long shot.

[Christopher Nichols]

Ok so this image shows the difference well. The best way to show it is with a very high quality HDR that has a very bright light source like the sun. The first image called dome light was easy. It was actually very hard to get any sort of result with the Environment slot, and the best I could was by turning up the IRmap and rQMC settign really high. Either way, it did not offer good enough results.

 

Keep in mind that there is no other light in these images. Just the HDR.

 

This posed a problem that Vlado came up with a creative solution with the dome light. As you can see, it is a no brainer.

[Stephen Thomas]

Ok so this image shows the difference well. The best way to show it is with a very high quality HDR that has a very bright light source like the sun.

 

Hi Chris, I appreciate your input greatly.

 

This is exactly what I am trying to achieve. At the moment I am getting very soft shadows, which is fine for dawn/dusk type shots, but not so realistic for obviously midday skies. I have been getting round this by combining with direct light using adv. ray traced shadows, but this involves trying to manually align with the sun on HDRI. If I increase the intensity too much, the whole sky looks 'blown'.

 

Is the problem down to the quality of the HDRI I am using or are there other settings I can use to solve this? I think I am right in assuming that the sharpness of the shadows is directly related to the number of f-stops in the original image. If so, can you (or anyone else) suggest a good source of HDRI files with the intensity range required? At the moment I am using Dosch Design's HDRI Skies.

[Christopher Nichols]

Is the problem down to the quality of the HDRI I am using or are there other settings I can use to solve this? I think I am right in assuming that the sharpness of the shadows is directly related to the number of f-stops in the original image. If so, can you (or anyone else) suggest a good source of HDRI files with the intensity range required? At the moment I am using Dosch Design's HDRI Skies.

 

You probably hit the nail on the head. It is probably the quality (color depth) of your HDR. Early HDRs and few since then have HDRs with a high enough color depth because most rendering engine can't handle them. As you can see in the image I sent you, it is nearly impossible to get a good result from the HDR with a bright source, using traditional methods of IBL. In that HDR, the sun has a value of around 36,000 (very high). The only place I have seen them higher is in Paul Debevec's which reach 1e7 (crazy high). But there are a few out there to consider. Consider any library made with a super high quality HDR collectors like the Sphereon or Panoscan, or someone that actually took the time to collect 15 to 25 stops of data. However, you will see that most of them are even scared to use bright sources because of that fear of bright sources. I think they should make some with sunlight in them, and only market them to Vray users ...

 

Some places you can try:

http://www.hyperfocaldesign.com/hyperfocal-sky-hdri-skies.html

http://www.doschdesign.com/products/hdri/Extreme_Hires_DVD.html

http://www.sachform.de/products/overviews/PANObase_Vol01_overview01_EN.html

[Christopher Nichols]

This is exactly what I am trying to achieve. At the moment I am getting very soft shadows, which is fine for dawn/dusk type shots, but not so realistic for obviously midday skies. I have been getting round this by combining with direct light using adv. ray traced shadows, but this involves trying to manually align with the sun on HDRI. If I increase the intensity too much, the whole sky looks 'blown'.

 

Also keep in mind that the method you describe is still perfectly valid, and I talk about a method very similar to this on my Exteriors DVD.

[padhia]

can .exr files work in vray?

[Stephen Thomas]

Also keep in mind that the method you describe is still perfectly valid, and I talk about a method very similar to this on my Exteriors DVD.

 

Is that a shameless plug Mr. Moderator??...lol

I've actually been meaning to treat myself to that for a while.

 

Not that I have any experience of this, but theoretically is it possible to create the higher intensity parts for the sun yourself and combine them with an existing HDRI using HDRIshop or similar?

[Christopher Nichols]

Not that I have any experience of this, but theoretically is it possible to create the higher intensity parts for the sun yourself and combine them with an existing HDRI using HDRIshop or similar?

 

I've tried to do that in Nuke and it simply never really looked right. Maybe I need to try other methods or do more research on it. Nothing really beats the real thing.

 

And yes you can use EXRs but they can't be read through the VrayHDR shader. You need to read them like a Bitmap using the standard max bitmap reader.

[Stephen Thomas]

Thanks for the info. The HDRs from Hyperfocal look amazing!

 

They also have a great tutorial on using HDRs in VRay which is a good starting point for anyone looking into this subject, which gives you a scene to texture and light yourself. Check it out at: http://hyperfocal.vismasters.com/catalog/viewproduct.aspx?product=3611&view_selection=Tutorials&pi=0

 

Anyway, for now I think I'll stick with what I'm doing as I'm getting quite good results. And I will check out your gnomon DVD Chris!

 

Thanks again, Stef