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In preparation for a shooting, I'm trying to match a 3d scan to a photo found online. The environment is 4 statues made of stone and I'm trying to match the shading and material for a future VFX shot.

My issue is that in my render, indirect lighting look way stronger than in real life (in shadowy areas). I have no idea what I could do to "reduce bounced light" or something like that. I'll explain below the exact issue.

The real-life photo

enter image description here

The Blender setup

My setup is quite simple :

  • The 3D scan as a mesh, with a generic stone texture found online
  • The wall behind and below it with the same stone texture and set to Indirect only
  • An HDRI for the world, that matches more or less the real-life photo
  • Render engine : Cycles
  • Color managment : AgX

Sadly, the most basic version of my scene is 300+MB. Too big for blend-exchange. Here is a version without packed resources.

enter image description here

My current result and the issue

For now, I have this result :

enter image description here

Which isn't too bad for a preview, but unsatisfactory. Here is the issue I'm facing.

enter image description here

In the photo, the surroundings of the shadows don't look to give much indirect light to shadows. It looks like the light in shadows mainly comes from the environment (e.g. sky). It is almost uniform, like a version of the shader of the stone just darkened a bit.

In my render, the shadows are heavily brightened up by the indirect light. We clearly see the indirect light coming from below. In addition to that, the indirect light seems more colored than in the photo (it may be just because of indirect light being brighter).

Note that my issue isn't about changing the exposure of the shadow areas. The issue isn't about the intensity of indirect light, rather it is about the distribution of indirect light in these areas. Indirect light from surrounding stone being too strong compared to the global indirect light in the scene.

Current solution

For now, the only thing I've found that helps is to reduce the saturation in dark areas with the following nodes :

enter image description here

It does improve a bit the situation, but still the indirect light from near the shadows looks way stronger. So it's not really solving my issue.

enter image description here

My question

What could be the reasons for such difference between real-life and my render ? What way should I go to improve the matchiness of my render ? Is there something obvious that would improve the situation ? Like change HDRI, change material, change exposure+lights, ...

My final goal is only to match the photo, anything else can be subject to change if needed.

Many thanks for your time !

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  • $\begingroup$ maybe your material is too reflective / too smooth? or maybe your sun light is not powerful enough. $\endgroup$
    – Luciano
    Commented Apr 24 at 14:37
  • $\begingroup$ @Luciano Thank you. The roughness is already set to 1, and I can't really just turn up the sun lights otherwise I have to darken the stone texture to compensate. The result would be identical. $\endgroup$
    – Lutzi
    Commented Apr 24 at 15:19
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    $\begingroup$ Real life light and shadows can't be replicated 100% in 3D by one light source only, in order to get more realistic light, you need to add some elements to make you get the result. To replicate one light bulb real life light, you probably going to need more than two or three light sources to get the same light in 3D, there are other elements that could also help, like Ambient Occlusion. When you do 3D Light and HDRI is a good starting point, but not enough $\endgroup$
    – Emir
    Commented Apr 24 at 18:11
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    $\begingroup$ Actually the opposite, even If you have the HDRI from the exact location, doesn't meant that only that should be you light, to match the 3D object with the real life one. The HDRI from the same location is a good start and from there tweak your light with other thing, as mentioned, Ambient occlusion is one of those, a light source placed in some specific areas and so, lastly, try to color correct your scene $\endgroup$
    – Emir
    Commented Apr 24 at 20:40
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    $\begingroup$ @Lutzi Actually Luciano is not totally wrong, the Sun at noon has a strength around 1000 W/m² (the unit Blender's sun lamp uses as well), so to get "realistic" lighting you could set the Strength to 1000. The thing is that our eyes can adapt to this and real cameras adjust aperture, shutter speed and ISO to not have everything blown out. So maybe when you adjust your scene to get the stone exposed correctly with that sun, the shadows might be more correct, too. But the render engine does not work exactly like real cameras, a render has no shutter speed, ISO or aperture to adjust exposure. $\endgroup$ Commented Apr 25 at 14:34

1 Answer 1

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In general - the issue you mentioned is problem of indirect distribution, you already know that. Shadow under crossed hands if fine, so problem come from bottom indirect rays (or HDRi side) ... you could try to eliminate it in shader. Also highlights in your render are darker (thanks to color management that is trying keep color range wider, some Look-Contrast could help). Anyway, instead of playing with all the color profiles and high dynamic ranges to restore non-existing light condition ... it seems to me straight forward for this purpose to just fake it :)

Cycles

At the end the setup is simple as hell ... there is not much to share ...

Here I used:

  • Sun - Strength 3,5
  • World - grey color 0.3
  • Color Management - sRGB - Standard
  • Material - is just image texture (sRGB) pluged into Diffuse shader

All the light adjustment is happening between World grey value and Sun strength (alternatively you can also use RGB Curve node behind image Texture node).

enter image description here

To better control indirect floor light I deleted all back wall floor faces and set solo material to back plate catching shadow of 3Dscan on the wall, but can be shadow catcher as well.

enter image description here

Sidenotes

I dont know what is your shooting story, but make it better integrated next to the statue figures, consider generate depth map (even as image sequence) used for displace rather than 3D model, because statue is kind of bass-relief so shape characteristics and light behaviour works a bit differently.

enter image description here

enter image description here

For more advanced integration I would take 360 equirectangular image at shooting location, that can be used as environment and source of light and like shadow catcher like in this video ... under the video is a link to BA for more info or here Shader for HDRi envi ... currently part of addon Photographer

Or reconstruct scene from 360 HDRi

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  • $\begingroup$ Thank you ! It's super interesting seeing another setup. I have a hard time appreciating Eevee but I reckon your answer is already better than mine. $\endgroup$
    – Lutzi
    Commented Apr 27 at 11:43
  • $\begingroup$ @Lutzi ... Just if you noticed the update to Cycles version ... Did it solve your issue? $\endgroup$
    – vklidu
    Commented Apr 30 at 21:09

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