Purple tips of tress with HDR Skies

[Archvis]

Hi Prom,

What is the best workflow then?

I have been using the exposure tools in the realtime renderer, however by the time I get the HDRI background to be the right brightness the foreground scene is completely whited out.

So why I need to play with the exposure is to get the the ratio of background to foreground ratio correct.

Or do you suggest I just lower the sun brightness?

Could you share with me a starter file with recommended settings for exposure with a sun and hdr background?

Thanks.

[Archvis]

I honestly think you're making your life much more difficult by using Max's exposure control. Use the exposure in Corona VFB or render setup - it's interactive, so you can see your changes while rendering.

Regarding your alpha channel/cut out mask, then don't convert the colored image itself in PS, but use the alpha channel to make a black & white mask image.

NB - "Premultiplied Alpha" is part of Max standard, and therefore it has been present in mr for ages. Nothing related to Corona

Hope it helps

Thanks for that reply.

The thing is, How do I control the ratio of brightness to the foreground and the background, at the moment the VFB is awesome and great for setting mood etc, BUT...

The background needs to be balanced and to do this I need to adjust the exposure of the background HDRI image / or tiff.

I'll attach an example.

[PROH]

Hi. It really depends on the quality of your HDRI background. Personally I mostly use either Sky & Sun or HDRI. If I occasionally use HDRI + Sun, then the sun will typically be set rather low (like 0.01 i.e.)

To change the exposure/strength of the HDRI background without changing the overall EV there are several options:
1) Change the exposure during import
2) Put the HDRI into a ColorCorrection map
3) Change the settings in the bitmap "Output" rollout (i.e. change the output value - like in mr)

If you want the HDRI not to be affected by the overall exposure, then do like DeadClown suggested: put it in a CoronaOutput map and uncheck (default) "Affected by color mapping". My personal experience with this method is, that it can cause artifacts in opacity materials like the one you're having, if the mask isn't 100% black & white.

Hope it helps