HDRi lighting with backplate rendering way too dark

[Terri Brown]

Hi guys,

 

I've been struggling for this one for ages, primarily because I usually just use an HDRi background as my backplate. Unfortunately there's always that ugly black horizon, which makes comping afterwards (especially when there are fine transculent details like leaves involved) a real mission.

 

Also in the imperfect world of commercial arch viz there is almost always a request for a contextual backplate - be it of the city skyline or whatever.

 

Up until now I have used a plane with an image mapped on (receive caustics and lighting switched off) as I can NEVER get Vray's environment background rendering correctly. Now I'm fed up and know this is possible, but can't figure out what I'm doing wrong. I followed this tutorial: http://www.hdri-hub.com/tips-and-tutorials/item/405-perspective-plate-match-in-3ds-max-2014-vray. It always renders either too dark or too grey.

 

Here's an example of the sky I have plugged into my Environment slot:

And here's how dark it renders out (sorry for the rubbish render but no time). Glass switched off:

 

Reinhard Color Mapping:

Gamma 2.2

Mult 1.0

Burn Val: 0.8

Affect background ticked (makes no diff ticked or not)

 

GI on, Brute Force and Light Cache

 

 

I even bumped the output settings of the sky bitmap up way higher than it should be but still not nearly bright/light enough.

 

Surely the bitmap should render as is? Why is it so dark?

 

Please help!

 

Thanks

Edited June 8, 2017 by terribrown

[James Vella]

because you have GI on

 

In the material settings set the material to self illuminated

[CliveG]

If that's just a standard image in your environment slot then of course it's going to be lacking the power of a HDRI or the Vraysky..... so just comp it together with something that has that lighting power: Either the long way in Photoshop - add in your own high dynamic range "sun" manually or cut and shut one from a donor HDRI if that's better / easier for you. Alternatively (and easier yet) just drop a composite in the environment slot with a base layer Vraysky overlaid with your preferred standard low dynamic range image, choose your blending mode to suit your taste, that will then give you the sun-angle control too.

[Terri Brown]

OK great thank you so much Clive. I will try that.

 

James it's just a bitmap applied to the environment slot, so there's no option to make it self-illuminated.

 

Thanks

[Terri Brown]

Clive I'm getting some very strange results here. Which blending mode would you suggest I use with the sky bitmap and the vraysky map? They all render such different results.

 

And in the VraySky parameters, I have enabled 'specify sun node' and for 'sun light' I have selected my Vray Dome Light with the HDRi map applied.

 

Is that right?

[Terri Brown]

Ok I think I got it. I put the VraySky map at an opacity of 50%, and added the sky bitmap over it with an Addition blending mode.

 

Seems better

[CliveG]

It differs slightly every time I do it Terri, depending on the bitmap and the scene. I often end up layering multiple instances of one or other of the layers to achieve the desired effect. Multiply and Addition are my usual blending modes and from experience I seldom end up with less than 3 or 4 layers (or more - I'll often slap a gradient in if I'm feeling arty).

 

Try layering a good sky map (I've removed the sun from a fluffy cloudy HDRI) with the Vray sky and you've basically got a fully controllable animate-able cloudy sky from morning to evening.... this does hit on loading times a bit though.

 

I think it's a great tool to add to the toolbox and I'm sure it'll become an easier workflow for you after a few goes and a bit of trial and error.

[James Vella]

In the bitmap settings you have a Tab at the bottom called Output. Set the Output Amount to 10 (default is 1). Adjust this up/down as you need