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Shadows on backlit objects - big problem (or - it's just me)


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So, in earlier versions of VW, I could create a cyclorama texture, backlight it just as I do in my day job and then throw a gobo or image onto it from behind. It seems to me this is actually no longer quite possible. The "backlit" shader allows a projector (aka spotlight fixture) to cast a beam of light onto the Cyc from behind, but, when the fixture has a gobo in it, only the full beam of light is projected, no gobo.


I prefer verisimilitude, and that's why I create renderings in the first place, so as to show clients something tangible, something I can say -"This I can do for you".

If I've missed something, I'd be grateful for the pointer/s.

I've attached links to two renders showing the difference between front projecting onto cyc and the same fixture, same gobo, etc from the rear and one img showing the shader settings...




Edited by mjm
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  • Vectorworks, Inc Employee

Hi mjm:

I am seeing the same thing now, it looks like the gobo texture is working on the backside but that the backlit shader is not using the masked shadow on the front side. I will ask Maxon about it, there might be some adjustment we need to do or the backlit shader may be limited here.

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Thanks for continuing to look into this Dave. Of course, what's somewhat ironic about this is my need for verisimilitude in creating a fake shadow. I hope there's an adjustment which can be made. This (patterns on a cyc from the rear) is a standard tool in the LD's arsenal and I use it regularly.

Edited by mjm
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I explored your File with C4D, and the good news are:

Yes they can!

But it has to be done by Nemetschek, there is a Option in the Backlight Shader

called Shadow Intensity that on default is on 60%.

If we get this Option also inside of VW, we can set it 100% and the result

is as extpected. In the current Version this Option is not available.

See C4D Screenshots attached. (Sorry for the German :-))

Besides That:

I like the Way Goboes are Exported from VW to C4D.

Nice little Gobo-Plate in Front of the Lightsource. Like in life. wunderbar simple!

Horst M.

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Hallo Dave,

Coming to monadnoc's question:

If you change the Shadow intensity (or make it available ;-), it would eventually be good to give us Control over the intensity of the Backlight effect by setting the brightness to control the brightness inside the shader. The one on top seems to have no effect.

This makes sense, if we use the Backlight-shader to illuminate the Scene by using Global Illumination aka VW Indirect Lighting.

The Value seems to be kind of multiplied with the brightness of the Light source.

Attached on image from a Test-file for a texture of satianted Plexi backlit from

a Circle Fluorescent Light.

Horst M.

Edited by Horst M.
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