Using HDRI on Indoor Scene

SandySims

I need someone to refresh my memory.  I want to use one of the many HDRI lighting presets on an indoor scene.  Say this one, Art Deco Hotel Interior.  I'm not getting the lighting or the background.  What am I missing?

 

 

SandySims

I need someone to refresh my memory.  I want to use one of the many HDRI lighting presets on an indoor scene.  Say this one, Art Deco Hotel Interior.  I'm not getting the lighting or the background.  What am I missing?

 

 

jbowler

SandySims said:

I need someone to refresh my memory.  I want to use one of the many HDRI lighting presets on an indoor scene.  Say this one, Art Deco Hotel Interior.  I'm not getting the lighting or the background.  What am I missing?

Turn on "Draw Dome"; create an Environment Options Nodule, got to Render Settings/Environment, turn on Draw Dome.  It's off by default on the "Load All!" scene:

Gordig

A fully enclosed scene won't let any of the HDRI's light through.

marble

Odd, I thought I read this question a minute ago but there was a different response.

Anyhow, that hotel scene looks unlikely to be HDRI friendly because you need to see all the walls and ceiling. What I usually do with indoor scenes is make the ceiling invisible and angle the camera so that it doesn't show where the ceiling would be. If I can leave a wall invisible as well, so much the better. Otherwise I use spotlights and emissive lights indoors.

Gordig

marble said:

Odd, I thought I read this question a minute ago but there was a different response.

Anyhow, that hotel scene looks unlikely to be HDRI friendly because you need to see all the walls and ceiling. What I usually do with indoor scenes is make the ceiling invisible and angle the camera so that it doesn't show where the ceiling would be. If I can leave a wall invisible as well, so much the better. Otherwise I use spotloghts and emmisive lights indoors.

Duplicate threads. I responded to the other one.

Richard Haseltine

Threads merged.

jbowler

The problem is maybe the ceiling domes, which seem to be set up to emulate outside illumination.  When I use the Iray exposure tool to measure the exposure required for the wall shown by Camera 12 (in the Camera presets, it's the third promo image) I get an EV of 11, which is way too high for an indoor scene given that it is a dark wall.  The scene does have "Blackout/Portals" in the "Base" bones.  There are four "Emitters" surfaces, they are all set to 10,000K (trying to match a blue sky) with luminance between 50 and 200 cd/cm^2 (from Iray Light Manager Pro).

I set the dome to san_giuseppe_bridge_16k from polyhaven.com, I set the EV to 13 (which is right for a bright outdoor scene) and got this:

That's clearly wrong; interior is pretty much never that bright!  I turned the emitters off but left the EV at 13 (so in this image the viewer is adapted to the outdoor illumination; the viewer has just entered the hotel lobby from outside):

We can see now that the ceiling domes are actually light portals, so for use with an HDRI it is necessary to turn off the emitter (this is done by setting the emitter color on the surfaces to "black"; easiest with Iray Light Manager Pro...)  I initially guesstimated this light level to be EV4, but the portals (the ceiling domes) really do add a lot of light, so I had to tweak it.  A useful trick to learn is to render to a window then pop open the pane at the left of the render window; modify the "tone mapping" EV value and, if necessary, hit Resume and the scene will show at the new light level pretty much instantaneously.  It doesn't have to be re-rendered (though if you turn on canvases it might start from scratch).  I ended up at EV9; this is what the person would see maybe a second after entering the lobby, still dark because of the bright domes and the window

:

It's not immediately obvious what the other emissive surfaces are meant to be; "Emitters_ring", "Emitters_square" and "Emitters_tube".  I set the emission colors to, respectively, blue, red, green to find out where they are as well as adjusting to EV8:

Blue - Emitters_ring, isn't visible here (it's behind the camera, and not very bright).  Red, "Emitters_square" is something on the RHS of the picture and Green, "Emitters_tube", seems to be some kind of hallway lighting which looks too bright.  I suspect they all need settings tweaked but I ended up turning off Emitters_ring, reducing Emitters_tube to 25cd/cm2 (from 200) and leaving "Emitters_square" unchanged.  I also changed the color temperature of everything to 1800K to approximate gas (mantle) illumination and rendered at EV8, reflecting complete adaptation to the interior conditions:

Notice that the hallway is now showing distinctly red-orange; that's correct for a viewer adapted to the outdoor lighting temperature (arround 6500K for midday)

It's actually a pretty bright interior scene, but the DAZ tone mapping implicitly assumes the much higher levels (32x) of bright outdoor lighting.  Normally I can sort-of fix this by tweaking the gamma in tone-mapping - the default gamma of 2.2 has a built-in viewing correction of about 1.1 for images of bright scenes viewed in mid-level environments.  This increases the contrast of the images when displayed which makes them seem brighter than the current viewing conditions.  The above picture is signifcantly too contrasty but tweaking the gamma does not seem to be affectiing the tone mapping as much as I expect.  I normally do this in PhotoShop.  In this case I set the EV back to 9 and upped the gamma to 3.0:

That's more like it!  I did render that one to a canvas as well, so I have an untonemapped version; I'll see if I can do anything better in PhotoShop.

jbowler

Here's what happens with PhotoShop "Local Adaptation" and +1Exposure (-1 on the EV - back to 8 but now with local adaptation).  I turned off everything else (details, saturation changes):

SandySims

Thanks Richard!  My bad!

 

Richard Haseltine said:

Threads merged.