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Light producing darker shadows on floor and background

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Xavier Bonet
Light producing darker shadows on floor and background
on Jun 3, 2019 at 4:09:40 pm

I have a scene illuminated by an Infinite Light with no Shadows because I want it to be a sort of flat, studio-like environment (it's not meant to look realistic, at any rate) but at one point a lamp turns on, using a basic Light that's placed inside the lampshade. Now, I want it to look like the light is coming from inside the lampshade, which would of course produce a cone of light that would cast down a circular light, leaving anything that's not in that circle of light un-touched.

Of course, in order for objects around it to stop the light (i.e. the lampshade, especially) I need to apply Shadow Maps (Soft), otherwise it just illuminates everything 360º around it, as if it were a naked bulb. The weird thing, however, is that instead of just adding to the light wherever it falls, in the case of the floor and the background it actually adds to the shadow! I.e, the parts of the floor and background that fall within the light remain the same, but the rest of the scene dims down, as if the light source that had just turned on actually "sucked out" the light of the rest of the scene...

LAMP LIGHT OFF:


LAMP LIGHT ON:


Perhaps it's a little difficult to notice te difference in shadows of grey between the two images... here's a split image that shows it more clearly:



Note how on the left the top of the cube is darker because the Infinite Light doesn't cast too much on it, as it's rather toward the horizontal plane; and the shadow underneath is caused by Ambient Occlusion. And on the right, note how the top of the cube is now lighter, as the light casts directly down onto it. Note also how the front of the cube is virtually unaffected, as the Infinite Light still casts on it as strong as usual and in the real world the fact that the lamp were turned on wouldn't cast a shadow on that face of the cube. However, note how the surrounding scene, i.e. the floor and the background, has darkened to be able to show that circle of light cast by the lamp... Notice how the circle of light is the same intensity as that part of the scene was with only the Infinite Light on it. So the only thing that's changed is that the surrounding has been darkened...

Now, I can "solve" this by excluding the shadows on the floor and the background in the Light's parameters but the issue is that the light itself doesn't affect them at all, so it pops out like the floor and background aren't really there when the light turns on because there's no longer any difference between what's inside the light circle and out... What I want is there to be a natural circle of floor and background that is more strongly lit than whatever is outside of that circle or under certain objects within the circle that are blocking the light, which should automatically be happening but, for some reason, it isn't.

I've never had this issue before...

Thank you in advance for any input!


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Brian Jones
Re: Light producing darker shadows on floor and background
on Jun 3, 2019 at 5:48:55 pm

post the scene file


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Xavier Bonet
Re: Light producing darker shadows on floor and background
on Jun 3, 2019 at 6:34:11 pm

Yup, you're right! Perhaps posting the scene will be the easiest way to go about it! ☺️

Here's the basic scene:
13398_lightissue.c4d.zip

The floor lamp should "turn on" starting on frame 15 (it's intensity goes from 0-100% in 3 frames).

Thanks in advance for your input!


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Brian Jones
Re: Light producing darker shadows on floor and background
on Jun 3, 2019 at 9:30:55 pm

you have a Compositing tag on the Floor with Compositing Background checked. "This option will cause the object to be self-illuminated yet still receive shadows." says the help. Fine for an object on a blank white floor like the example image in the help but here everything is bright white until you introduce a shadow and it has to darken for the shadow.


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Xavier Bonet
Re: Light producing darker shadows on floor and background
on Jun 3, 2019 at 10:24:57 pm

Hum! You're absolutely right. Having got rid of the Compositing Tag the "natural" state of the becomes as dark as the shadows.
I can see an obligatory workaround coming!
I guess I could get rid of the bg and turn the floor into a transparent shadow receiver (to receive the Ambient Occlusion shadows, really). Then in AE I can throw a solid of the color I want behind everything. And to replicate the bright circle on the floor (which is now a bg solid in AE) I can export a still of the light doing it's thing and casting all other objets's shadows on a plain white floor (all of the objects hidden from the camera)... that way, the I have a matte layer that I can then composite in AE through add, thereby adding brightness to the solid where the light would hit on the floor.
Does it sound too convoluted? Is there an easier way of working around what you've found?
Thanks for the input!


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