control how much an object casts shadow?

[andrewjohn81]

I have an opaque object and want it to basically cast shadows at say 27% instead of 100.

Is that possible?

I can't think of a way of doing it other than compositing.

[Da_elf]

cant think of a way to do it on object basis but you can do it in the lights shadow peramiters. although im not sure why you would want an opaque object to cast a transparent shadow

[andrewjohn81]

a few objects are seeming to collect much darker shadows than other. We just wanted to think of a way to lessen them without making a bunch of extra lights.

I know i could create one light to illuminate the objects, then create one light for most of the shadows excluding the other objects, then create yet another light for the object we want to have less of a shadow and have it exclude the other objects.

That's kinda drawn out for what we want though, especially if you just want to control of it on a per object basis. you'll end up creating 2 lights for nearly every object to get exactly what you want and that would be rediculous.

Hopefully we'll get a shadow controlling map like mental ray has (although I don't know if MR has it for max at the moment. it works in maya great though). That'll at least control the shadows per material.

[visions]

I read a post by Valdo that if you use a standard light with Vray shadow and uncheck Transparent Shadows, then you can control the color / darkness of the shadow like in a normal ray traced light.

Hope this helps
Vivek

[Morbid Angel]

well the method discribed above will affect all objects, or a per object light will need to be created.
If you think physicly, this is not correct. As infact all objects in the physical world cast the same shadows. The difference in shadows are defined by objects properties i.e. transparency or gi luminance transmitted though the object.
So direct answer would be no its not possible to make some shadows less opaque. Only by method of cheat or comp.

[Clifton Santiago]

What I would do is clone the desired object on top of itself, then exclude one from casting shadows and exclude the other from being visible to camera. Then make the shadow-casting object 27% opaque.

[paulison]

I also find vray shadows too dark at times. In terms of pysically correct, vray isnt...

you could have a scene perfectly set up with currect lighting values and materials and there will still be many places where shadows are much darker than they would appear in the real room. Its like there isnt as much light getting to these areas as there is in reality. You could argue that this is because the wrong colourmapping was used or to adjust something, but in the end you are simulating that space and all we can go by is how the image looks and if it is going to be appealing. This isnt so much of a problem with interiors using LC (because they always seem to look great!), more so with exteriors using IR+QMC I've found. So basically I think it isnt pyhsically correct and you have to end up faking things anyway which is why being able to adjust shadow transparency in the vray lights would be a nice option rather than having to render out to seperate layers and adjust manually in photoshop. Good to know you can do it with standard lights using vray shadows though

PS a good example was that mercedes interior animation someone did last year. he ended up using a vray dome light or something and no GI at all because the vray lights were not lighting up the interior enough to look marketable. It may have been correct to have really dark areas, but it didnt look as good. if the vray lights could have had their shadows reduced im sure he would have used this method + GI instead. The lighting was totally faked but this animation was awesome.

Maybee a global vray shadow transparency would be nice? lighting could be precalculated and be able to rerender with a diffrent transparency value using the saved map. Or how about a contrast value because in the bright areas you would want the shadows to stay the same, but the black shadow areas you may want them to be less intense.

[mike.edel]

sounds to me like a problem of perception rather than rendering

our eyes usually adopt to the lighting situation (like when you point a video camera with automatic exposure metering from bright areas into the shadows)
the dynamic range of display devices is too limited to allow for such effects

so physically the rendered scene might be correct, but the image and therefore the perception is different from what you'd expect

the best solution is to cheat
exclude the offending shadow-casting objects from the respective (shadow-casting) light sources, clone those lights, include only those objects and lower the shadow values (was it called density?)

shouldnt be much slower than before (but it should be faster than using stand-in non-opaque objects to lower shadow density)

cu mike

[chicoone]

G buffers and elements offer many advantages= control, flexibility and wide-open options:

http://www.3drender.com/light/compositing/index.html

http://www.chaosgroup.com/forum/phpB...r=asc&start=75

Blevins and Nichols teach these thing for a very very good reason!

Ismael

[Sushidelic]

There was a material by blur called "RaytraceShadowTransparencyOverride" which used to work with Vrayshadows, but I dunno if it still does. There you can set the shadow tranparency on a per material basis.

Might help,
Michael

Edit:
link http://www.blur.com/Tech/zip/rayshadoverride.zip

When using raytraced shadows, this material allows you to map the apparent transparency of the object differently than the default shadow color/density. This gives you a lot more control of shadows than regular materials do by default

[andrewjohn81]

that's pretty much exactly what I am looking for.

In mental ray there is a shadow shader, which basically tells every light in the scene how to react to any object it hits which has that material applied.

If I had created some clever falloff maps to create a sss like object it would still be completely opaque according to the light. This would force me to create another light that only casts shadows. that's annoying and isn't as efficient.

A good example of this is green tupperware. You know that old tupperware that you couldn't see through, but light passed through it fairly well? Anyway, it casts a greenish shadow because of it's material, but there's no way I would waste an actual raytraced sss shader on some simple prop in my scene.

A shadow shader to apply to any material would be super anyway. Look at the way mental ray creates theres. it's really a nice method. It can be more difficult to learn, but it's powerful as hell.

We should be able to manually override any section in the shaders.