Matte Shadow

[Rhodesy]

Firstly im using the C4D version so maybe this is just a current limitation in the implementation....

With vray I have the option of Matte shadow in the multipass options. When in photoshop I can switch it to normal blending mode, invert it and then switch to multiply and I have a nice clean shadow pass overlay that I can use to either paint in stronger areas of shadow or have shadows over comped objects.

The shadow pass in the corona file has all sorts of colour information in it and when I do the same thing it looks strange and adding odd colour hues to objects. In the Max version is there the option for a matte shadow pass or is there only the shadow pass which includes these saturated colours?

Thanks

[maru]

I think there might be still some limitations regarding this in the C4D version, but maybe I could help you. What exactly do you need? What do you mean by "shadow pass" - is it a pass you can overlay on an image to get black/dark shadows?

[Rhodesy]

Hi Maru, sorry for the late reply. Yes essentially thats it. A pass/layer that can be used to enhance the shadows of a scene in photoshop or be stacked on top of a comped layer for example a grass image that needs a buildings shadow cast on it.

The current offering doesn't give exactly what I want as it includes coloured shadows for the whole scene rather than just that coming from the sun. Best shown in the attached examples...

If you invert the vray one and set it to multiply it gives a nice shadow catcher effect for the whole scene which can be masked and painted in where required.

[Rhodesy]

Just wondering if anyone can confirm the shadow pass is the same in the MAX version - i.e. coloured and also more of a GI shadow rather than just direct light? Or is there another pass which does this? Thanks

[TomG]

Works the same in Max as shown here - I think though the purpose of the element is different than the uses you describe (which sound more like a shadow catcher, e.g. adding the shadow of a building onto a backplate of the environment?).

The element description is "Shows the shadows (energy subtracted from the image due to shadow ray occlusion). This is the complement to the beauty pass, showing white where there are black shadows. If this pass is linearly added to the beauty pass, it negates the visible shadows. Note that currently the shadows from environment lighting are always shown, resulting in a washed-out pass in typical interior renders." (from https://corona-renderer.com/wiki/render_elements)

So rather than strengthen shadows as noted in your uses, it removes them if you add it on top of the beauty pass, and for that it would need the colour component in it. In some quick and simple tests, using it in Subtract mode does give the effect of enhancing shadows (and again for that it would need the colour component, I believe).

[Rhodesy]

Thanks Tom. Is there / will there be an equivalent pass as the vray one in corona as its really handy to have a scene wide shadow catcher one click option? I have tried the direct pass as well be that's not quite right either.

[TomG]

Thoughts, from 3ds Max haven't tested in C4D yet

- The "GI effects in the shadow pass" when I tested was only because I had an Environment active (so, it was casting its own shadows). If I turn that off, then I get shadows from light sources only with no "GI effects" in the shadows from light bounces. So to get the effect like the one I believe you are looking for would take a separate render pass with any HDRI / Environment turned off. The CShading_Shadow doesn't discriminate in what is causing the shadow.

- Could either desaturate after rendering, or do a separate pass with a material override, in order to remove colour information (but see below)

- Handling objects with transparency (or opacity <1) would require thought, for instance you couldn't use a material override if you wanted to preserve that, and adjusting Exposure and / or Contrast may be necessary to see different strengths of shadows (depends on whether you need different strengths, or just "all or nothing")

Sample image where I adjusted Contrast to 10 so that the shadow for the semi-transparent sphere was less strong than the solid cubes, then desaturated in post, which looks much like target look that you posted. Does need the separate pass without Environ though, unless you want the shadows from that included (and that would depend on intended use of the layer).

EDIT - and inverted the image in post too.

[Rhodesy]

Thanks for the reply and investigation Tom. I would have thought it would be easy to separate the direct lighting from the GI and create a shadow pass, particularly with the new 'multilight' implementation so perhaps it might come in with that? I wonder what others do in this situation as its surely a common requirement for comping stuff in post. Could you pass this request on to the devs to see what they say? Thanks

[bastille]

Hello,
I'm looking exactly for the same thing. I have a lot of packaging to render and it's very usefull for me to have each shadows from each lights isolated. For now, I'm creating a new scene , switch to vray and used rendermask :)
Pierre