[mahoosive]

Is there a simple way of using a modo style shadow catcher without the need for post compositing?

In Modo I have 2 environments, 1 visible to camera that provides my background image and a separate environment that contains an HDRI providing the lighting. My object sits on a shadow catcher and in the render it looks nicely in place on the background photo.

Trying to render this with maxwell doesn't seem to work. I've tried to work out the maxwell alternatives but am not having much luck. If I apply the 'matte' and 'shadow' properties to the ground plane material then I don't get anything on the shadow pass. If I only apply the 'shadow' option and try to re-comp them all together in photoshop then the shadow layer is so noisy it looks terrible, even though the beauty pass looks great.

Can anyone give me a hand?

[Marton Day8]

Hello mahoosive,

If you want the 2 different environment effect in Maxwell, use IBL environment. For the background image use your background picture and for the other channels (Reflection, Refraction, Illumination) use you HDR image to light your scene.


Shadow catcher:
Do you need a matte object? The matte material "cuts" your object, so if your object sits perfectly on the shadow catcher plane for example, it doesn't worth to use it.

A) Let suppose your object sits perfectly on the shadow catcher plane.
Just turn on the shadow check box for the shadow catcher material, select the shadow catcher object, go to Object Parameters and check the Hide from Camera check box. (So the shadow catcher object is not visible in the beauty pass, but the shadow will appear in the shadow pass)

B) In case you have to use matte material because your object continues behind the shadow catcher object.
I suggest for you to clone the shadow catcher object. You can use one of the shadow catcher objects to cut your visible object (set the matte material for this, without shadow), and the other one to produce the shadow pass (use shadow material without matte, and set the hidden from camera flag). It is important to move the second (the real) shadow catcher just a little bit to cover the matte object, otherwise the matte object will try to cut through the shadow object, and it won't look good.

Tip: use the new 2.1 version of Maxwell, because it produces nicer shadows.

I hope it helps!

Márton

[mahoosive]

Hi,

Thanks for your help Marton. I can't get IBL to work at the moment. Despite me putting the HDRI map in the Background, reflection, refraction and Illumination slots it says there is no light source when I try to render.

I'll play a little more this week and hopefully I can get it working but it's not behaving as I would expect at the moment.

[Marton Day8]

Please make sure you use a high quality HDR map. There are many HDR images on the net without real HDR data. From these images it is not possible to take out adequate light information.

Or if you want, you can send me your scene and I will check it for you.


Márton

[mahoosive]

Hi Marton,

It turns out that you must have the Environment map turned on in Modo, even if you are not using it and have assigned maps in the IBL global settings. If this map was turned off then maxwell thought there was no lights.

Does the background map have to be an HDRI? I was hoping to have a screen mapped JPEG in the background and use the HDRI for reflection, refraction and illumination.

Thanks

[Marton Day8]

Hello,

You have to use HDR,EXR or MXI on all the IBL channels. But for the background you can try to convert your jpeg file to HDR (it is a fake HDR in this case) and use that, because the real light information comes from the other (reflect/refract and illumination) channels. (But it is a very silent and non-official advice, I don't have any idea how good or bad the result will be....)

In modo you can force the plug-in to use the IBL background and don't care about the modo environment settings if you switch from automatic environment to IBL environment.

Márton

[Marton Day8]

And you are right, if you don't have environment material or the environment material is not visible in modo, the exporter exports the scene with "None" environment. Have you intentionally turned off the env. mat in modo? Is there a benefit? (In that case I should solve it for the exporter....)

Márton