Problem with dome light

[tsponti]

Hi,
I need yu guys because I reaaly don't understand one thing with a HDR file.
I buy the 1103 HdR file of Peter Guthrie.
When I load it in my dome light texture I have different render while I only change the HDR orientation.
Here are my settings, quite basic I think.
Can someone could help me with that?
thansk a lot!
thomas

[Micha]

Best you make a test and turn you camera so that you see the HDRI as background (use a wide angle). So, you could see what happens.

-Micha

[tsponti]

Hi Micha,
do you want I send you the 3DM file and the HDR so you can test?

[tsponti]

here ares some new tests with a different view.

[Micha]

Interesting - yes, you could send me your scene and HDRI.

[Micha]

I got your file and test it. The problem seems to be that we have a small strong light source, the sun. The light dome is using a smaller resolution of the HDRI for lighting. Per default there is set texture resolution 512. If you turn the HDRI around, than some times the sun is particular lost by the internal resolution conversation. I tried texture resolution 2000 and it works much better, the brightness is constant. I don't know what will be the disadvantage of a higher resolution, maybe the chaosgroup team can tell more.

Here you find a little info about the texture resolution only:
https://docs.chaosgroup.com/display/...Ray+Dome+Light

[tsponti]

Thanks Micha.
it's a little bit strange because those HDR (from Peter Guthrie) are supposed to be very good quality.
do you think they are not good? where do you find good ones?

If ChaosGroup Team can tell me more about the HDR texture resolution and how to do good with?
thanks in advance.

[Micha]

No, the HDR is great. The light dome has a special texture resolution parameter that cause, that for lighting the HDR texture is down sampled. I suppose so the calculation is faster, if the HDR is internal down sampled.

[tsponti]

Ok, so in general you recommend to put the texture resolution at 2000 for Dome Light using HDR ?
the default is 512, we need to increase it everytime?

[Micha]

I don' know how to best use this parameter. I never used it. I hope the Chaosgroup team can help you. I did some quick tests here and it looks like the RAM usage will be increased, but not dramatically. So, I would go with 2000.

[Peter.Chaushev]

My colleagues from the Support team have advised me the issue discussed here is due to the overall high pixel values of that particular HDRI. The difference should be less noticeable in V-Ray 3.6 for Rhino.
Regarding the Texture Resolution parameter - it controls the size of the HDRI texture used for presampling calculations. This mainly affects objects illuminated by the Dome light and its appearance in their reflections.

Kind regards,
Peter