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I really want to use an hdr for reflections in my rendering, but prefer to light with physical sky or sky dome. I realize that this can technically be achieved using Image Based environment, then only using the hdr in the reflection channel. However, it doesn't actually work for me. I can only get the hdr to be in my reflections if I also use as the Illumination channel, which I don;t want to do since it is super dark and washes out my render.

Anyone have any advice?

Changing the exposure of your camera and/or the intensity of the IBL will help alleviate the "super dark" quality... about soloing it for reflections, are you sure it isn't already doing it properly and it's just too dark to be seen?

Best,
Jason.

Here is a test image rendered with HDR Illumination:


Note the reflected sky in the mirror material on the ground, and in the window of the building. Slight reflection in the water.

With super high ISO that burns out the background:



Here is the image with all same settings (not ISO though), with no Illumination channel:


No reflection this time.

It's really hard to say without having access to the HDR and scene, it could be that it is just a poor quality HDR.

Also it is somewhat difficult to judge partially because you have the main light source coming from 2 different places in the renders -- in the first is coming from the direct right, while in the second it is slightly behind us and left...

But if I had to guess I'd just say the HDR is not very good.

I'm also abit confused are using a couple of HDR images for different channels or attempting to mix the physical sky into only some channels?


Best,
Jason.

Here is the image using a different hdr (RADSKY_017):


Basically the same results (still ISO of 3000)

SU settings:

btw. why are you using iso 3000?

Yeah, those HDR samples from Dosch are not really the best -- try the free sample from here: http://www.hyperfocaldesign.com/

Best,
Jason.

It works just fine for me over here with a quality HDR/EXR... and the EV was a reasonable 14 (to match the physical sky/sun illumination).
Best,
Jason.

here too... with sky dome

numerobis wrote:btw. why are you using iso 3000?

Because if I use the HDR as the Illumination channel, my render becomes super dark.

I already said it (and showed it), but it's worth repeating -- boost the IBL intensity... and for those Doosch samples it has to be boosted by quite a bit.

Best,
Jason.

Here is the image with HDR for all channels except illumination:



Here is the same image with everything the same except HDR Illumination turned on:



Notice the sky being reflected in the mirror on the ground, and the water. This is using the free HDR you suggested Half Life.

Also, what is IBL?

Half Life, I just noticed you were using a much higher intensity for these channels than I was. Here is the result when I bump them up to 20 like yours (with Illumination off):



Much improved. Is that what you meant by IBL?

Yep, you are on the right track now... all you have to do is find the right combination of Intensity and exposure values to achieve your desired effect.

IBL= Image Based Lighting

Best,
Jason.