Shadow Catcher doesn't work with Spot Light - see attached examples

Steve P.

- The Shadow Catcher plane does not work when I use Spot Light and Iray.

- Same issue if I use the built-in ground ("Draw Ground" ON)

 

Please see the attached image, or read my findings below.

 

TEST RESULTS:

Shadow Catcher OR “Draw Ground” together with.. 

    Distant Light

        Result: shadows are OK

 

    Mesh Light

        Result: shadows are OK, but it needs extra steps.

        Step 1) I need to select the Mesh Light and then run the “Create Advanced Iray Node Properties” script.

        Step 2) tI need to enable “Iray Matte” for the Mesh Light in Properties.

 

    HDRI Dome only:

        Result: shadows are OK

 

    Sun-Sky only:

        Result: shadows are OK

 

    Spot Light

        Result: shadows do NOT work (no shadow at all), no matter what I do. I read many forum posts, but I didn’t find the answer.

 

Can someone please help? Thank you!

I am using Daz Studio 4.16 on cylinder MacPro with Mojave.

 

Richard Haseltine

I think the issue is Tone Mapping - if you have only the spot light it is probably fairly weak with the default values, and so there is little difference between shadowed and lit areas of the catcher. if you ramp the ISO up, or otherwise increase exposure, the shadow will start to appear.

Steve P.

Hi Richard, thanks for the quick response. I tried, but it's not that, I can turn the ISO or the spot light’s power to even 1 trillion, there is no ground shadow. But I read that people had the same issue.

 

Just to clarify, this is the test scenario:

    - there is only one spotlight, no other light (no HDRI or anything)

    - there is only a character and a shadow catcher (or "draw ground" ON)

    -  using IRAY in photoreal mode.

 

Have you, or anyone, successfully rendered shadows with the above mentioned simple setup? If yes, can someone (if time allows) show the Spot Light and Shadow Catcher's setting with a super quick 1 minute video / or screenshots?

Since other people reported this in earlier conversations, I am convinced that this is probably a bug.

Thank you for anyone's help!

Richard Haseltine

It fades out quickly, because of falloff, but this has a default spotlight, a sphere, and a plane with Iray Matte - it seems to have shadow and bounce light (the light is on the side away from the camera):

Steve P.

Yes, but your scene only works becaue the "Base Color" of the shadow catcher is set to white, am I correct?

I also have shadows if the "Base Color" is white, but that's not the solution and it's wrong. The base color of a shadow catcher must be black, otherwise we'll have issues when compositing the render with a photo --> we'll get a washed out shadow area. However, if the base color is black, then everything is perfect when compositing the render into a photo. 

Now, the problem is: all other lights cast proper shadows when the "Base Color" of the shadow catcher is set to black, except the Spot Light, that only works if it's set to white. So it's a bug, unless I am missing something.

 

TEST:

1. Try to set the base color of the shadow cacther to black, I am almost certain you won't have shadows with a spotlight, but you will have shadows eg. with distant light.

2. Instead of a plane, use "draw ground" ON, and leave the ground reflectivity as pure black (as it should be). You won't have shadow with a spotlight

Richard Haseltine

Yes, I see that with Base Colour set to black - though i'd think it was the other lights that were then wrong, black shouldn't catch shadows since it is already wholly dark.

cgidesign

Shadow catcher in DS 4.16.1.21 beta.

Matte object with black surface does not show shadow from spot light. Bug ?

Steve P.

I made countless experiments, and I really think the base color MUST be black (at least for most use-cases)

EXPERIMENT (A)

1) If the Shadow Catcher's color is set to white, then we have a massive issue when compositing the render into a real photo. Basically, we end up with a large muddy / whitish area, and the render is basically unusable.

2) But if the Shadow Catcher's base color is black, then the render is 100% perfect for compositing, the shadows looks 100% realistic

So I don't think it should be white at all..

 

EXPERIMENT (B)

- Please also test with the built-in ground. The one which is inside the Render Tab --> Environment settings --> draw ground: ON

- This ground works as a Shadow Cather

- But it does not work with Spot Light either, unless you change the "ground reflectivity" to a light gray color, or white. Again, very similar black vs. white issue, just like with (A)

- But there is a reason why the default ground reflectivity is black, that's the best general setting, which is OK for most cases. And it works with every other light, except the Spot Light.

I am 99% certain that it's a Spot Light bug, and I am also 99% certain that the Shadow Catcher's base color must be black. I can help your developers to demonstrate why compositing requires black shadow cacther, just let me know if they need further insight.

Thanks

 

 

 

  

cgidesign

I opened a bug ticket about it. Maybe you can do so as well? The devs then know its not an issue with only one DAZ Studio installation.