[mjcherry]

So, I'm working on a new interior scene, a Parisian atelier at golden hour, and I w have some big beautiful windows and a skylight (I will share basic render later). Outside the windows, I have a plane with an image of Parisian rooftops as an emitter. Right now I also have a physical sun and sky so that light will really stream in through the windows. I would like to add an HDRI environment map to the scene to help light the interior. Is this possible? If not, what would your recommendations be?

Thank you so much for the help!

Best,

Matthew

[Mihai]

I'd try by saving your current Phy Sky to an HDR map (you can do this from the Save menu in the Sky settings), and then add it to your existing HDR in PS using linear mode. This should keep the strong sun from the Physical Sky while also giving you lighting from the "original" HDR.

[mjcherry]

Sweet, I'll give that a shot

[LadleSky10]

Ah, well this is surprising. I've been using the Physical Sun & Sky with an object plane in front of the window (camera visibility off) and attaching an emitter material set to area light. The emitter uses a HDRI as its light source. Seems to work just fine. So, I'm assuming the HDRI export method above is more accurate but what are the pros and cons of the two methods? (And too, perhaps I'm not understanding the question. )

[Mihai]

That works if it gives you what you want I was replying more to what Matthew mentioned about wanting to also add an HDRI environment map mixed with Phy Sky, because he said he's already using an emitter by the windows, besides the Sky/HDRI combo he'd like to use.

I'd just mention though to take care when using LDR images as emitters because it might not work very well, especially if the original image is of a scene which should have a large exposure range, for example a photo of buildings and sky. In reality almost of the light coming from that "emitter" would be from the sky part. If using an LDR photo of that scene as an emitter it may not look right because all the pixels in it will emit at almost equal strength.

As an example here is an image emitter using an HDR I took of a shop window at night, illuminated by spots and a very strong neon sign. Difference in emission strength/color between using the HDR version as an emitter and an LDR photo from the same sequence, and with different exposure settings of the render:

[Forum Moderator]

Ah, well this is surprising. I've been using the Physical Sun & Sky with an object plane in front of the window (camera visibility off) and attaching an emitter material set to area light. The emitter uses a HDRI as its light source. Seems to work just fine. So, I'm assuming the HDRI export method above is more accurate but what are the pros and cons of the two methods? (And too, perhaps I'm not understanding the question. )

I just read your reply and thought that probably your plane is occluding physical sky and sun, as setting it as hidden to camera makes it invisible to the camera, but it still casts shadows. If you want both things (the plane and the sky) to combine you should add a "ghost" BSDF to the emitting material of the plane, so it doesn't cast any shadow and occlude the physical sky light.

A ghost BSDF is one that has fully white Transmittance and Nd=1. That renders as vacuum, so when the light is turned off, it shows nothing instead of black.

In the case brought up by Mathew, he could add a sphere around the scene (with normals pointing in) and assign an emitter with the HDR plus a ghost BSDF. With this method, you can mix both illuminations or get two different illuminations by using Multilight.

Cheers!
Fernando

[mjcherry]

This is so awesome

[LadleSky10]

Ah, yes, I am doing exactly that! Thanks for reminding me of it --and sorry that I neglected to include that bit of information. (In fact, I can't remember at the moment but I believe that I learned about this method either from one of Mihai's tutorials or the Maxwell on-line documents --which is likely why I haven't encountered any problems!)

I've been experimenting with the second method Mihai mentions above (combining hdri's). Seems interesting (although, I encountered total blow-out results saving the physical sky at first --decided that I probably needed to disable the physical sun ). Next, I'm going to start some tests to compare the results of the two methods!

[LadleSky10]

Oh, okay, just noticed your tweaks regarding the 2nd method. I'll start experimenting with that instead. Thanks Fernando!

[mjcherry]

Fernando,

I just want to add that having you active in the user forums is extremely helpful.

[mjcherry]

As promised, here is the image that I'm working on. I'm currently in the process of creating textures for the objects and some are still just my base lamberts. The Parisian rooftops is a plane with an HDRI emitter assigned to it. I have a physical sun and sky providing most of the light. I have completely walled off the set and on the two walls you can't see, I've assigned a interior HDRI emitters (because I didn't know how to do what Fernando suggested, but I'll try that soon).

Any critique that you can offer as to the lighting or the materials, please let me know. As always, I'm going for a photorealistic result and, while I feel I get close, I'm not sure if I really achieve it.

Thank you everyone!

[LadleSky10]

Here's how I've been setting up the hdri emitter (ghost emitter). Hopefully I've set all the parameters correctly!

[LadleSky10]

And here's how I've setup the sphere with the normal flipped --loaded in a sphere from the library, scaled it up and flipped the normal, then added the ghost emitter material to it. Is that correct? BTW, thank all of you guys for the great information I'm getting from this thread!!

[seghier]

As promised, here is the image that I'm working on. I'm currently in the process of creating textures for the objects and some are still just my base lamberts. The Parisian rooftops is a plane with an HDRI emitter assigned to it. I have a physical sun and sky providing most of the light. I have completely walled off the set and on the two walls you can't see, I've assigned a interior HDRI emitters (because I didn't know how to do what Fernando suggested, but I'll try that soon).

Any critique that you can offer as to the lighting or the materials, please let me know. As always, I'm going for a photorealistic result and, while I feel I get close, I'm not sure if I really achieve it.

Thank you everyone!

beautiful render ; the texture of the wall look it have repetitive element ?

[Forum Moderator]

Fernando,

I just want to add that having you active in the user forums is extremely helpful.

Thank you Mathew! I'm happy to help.

Regarding your setup, LadleSky, everything looks correct.

I made a small screencapture gif showing how this can be done, but I think you got it right:

https://drive.google.com/file/d/16vtAOJ ... sp=sharing

Cheers!