preventing certain objects from casting shadows

sriesch

For a given light source, is there any way to prevent selected objects from casting shadows, while still allowing the other objects in the scene to have shadows?

I'm not desperate to find a way and I'm sure I could fake it if I really had to, I'm mostly just curious if there's a simple way I'm overlooking because it would come in handy on occasion.

SimonJM

Yes, there is ... but as I have a render going full-tilt atm I cannot guarantee the answer! There are two things you can do (depending, I think, on the shader in use on the relevant surfaces) with shadows - cast/not cast and be visible or not in render. One of those will only work with Deep Shadow Maps. In the properties you will see in the Surfaces tab there will be (amidst all else) two buttons, one named Fantom, the other to do with Shadow casting. Fantom, I think, makes the surface invisible in the render, but still shadow casting, and the (relevant) button will stop the surface from casting a shadow.
Having said there are two things, I believe there is a third: 'catching' shadows or not.

I did this a while back - one render, two figures, one shadow :)

Richard Haseltine

If you want to stop a whole item from casting shadows, just click off the Cast shadows property in the Parameters pane.

sriesch

thanks!

Marshian

Hi Forum!
I've created a prop that has three material settings, two of which are ubersurface. Each material relates to a separate prop and the props are positioned inside each other like Russian nesting dolls. The challenge is that I'd like for only one of those surfaces to cast shadows and the Parameters Tab/Display/Cast Shadows affects all three surfaces (either all off or on).

Is there a way to have only one of the surfaces cast shadows?
Initially this was three separate objects and I could control this but I combined them to make this a more user friendly prop.

thanks in advance for any help!

Richard Haseltine

Are all three items listed in the Scene pane or have you turned them into a single item? If they are all listed you should be able to select one and set it separately, if not then You will be somewhat stuck.

Marshian

Thanks for the confirmation, I thought this was the case. They are all one item in the scene tab but I have a back-version as separate items, I'll go back to this one. To solve this I'll parent the smaller items inside the larger- that way when it's clicked on the larger item can be repositioned /scaled and the others will follow.

Ultimately this is good news, it will save a lot of time to keep these separate.
Thanks Richard!

Skelch

I hope no one minds me necro posting, but this thread was so helpful to me I had to add my thanks, after all this time I have never needed to turn a shadow off of an object until now. I kept looking in the surface tab and not the parameters. Thanks so much!

Ptrope

Richard Haseltine said:

If you want to stop a whole item from casting shadows, just click off the Cast shadows property in the Parameters pane.

Is that something specific to a type of object? I don't have that in my Parameters tab at all.

EDIT: further Googling found me the note in another thread that changing IRay rendering from Photoreal to Interactive returns this parameter item.

 

kitakoredaz

nowdays I do not play with 3delight ,but remember those property as visible when you use 3delight render. 

if you use iray your render engine, the property not work. (though you can set it as visible, in parameter setting)

you may need to use canvas (render Advanced tab) , then need to compsit I think. 

kitakoredaz

unftortunately ,with iray photo real, and (daz canvas setting), I can not find simple correct way to remove only  one node shadow  from render image.

if I hide obj with iray canvas (not include the obj, then use canvas), it still generate shadow, and reflection  of the obj.

if I hide obj from scene, then render, it remove shadow, and remove reflection from the obj too.

Actually I serch google, if there is LPE, but I just see, there seems no LPE which can remove shadw of one obj, I think.

 

I can use Material ID, then can make mask about each obj too.  and could composit,  but can not make mask for the shadow only which generated by one obj I think.  then if I remove shadow of the obj by composit,, which can not cast reflection from the obj anymore. 

Mage 13X13

I want one of the objects in certain renders to not accept shadows from existing lights. The object is supposed to be an effect that has a glow of its own. I made it translucent, so that objects and backdrops can be seen through it. It alread does not cast shadows, but I need the shadows of other objects that intersect the effect object to not show on the effect object. I know about shadow catchers that will catch shadows on an invisible surface, but I need the opposite. Please help.

Richard Haseltine

Mage 13X13 said:

I want one of the objects in certain renders to not accept shadows from existing lights. The object is supposed to be an effect that has a glow of its own. I made it translucent, so that objects and backdrops can be seen through it. It alread does not cast shadows, but I need the shadows of other objects that intersect the effect object to not show on the effect object. I know about shadow catchers that will catch shadows on an invisible surface, but I need the opposite. Please help.

That isn't possible - if the object takes light from a source then it will be affected by shadows, even if it is also a light source, and iray is literal-minded in its emulation of light.