Ambient Occlusion with shadows turned off and object invisible.

[3daltm]

Hello everyone. I use dirt on walls a lot. And sometimes I need to use invisible objects without shadows to create dirt. To solve part of this, I use Corona Distance, but unfortunately, the effect is almost never as expected because the dirt is projected upwards and downwards. I think the solution can be achieved with two options: 1 - Allow ambient occlusion to detect invisible objects without shadows, or 2 - Allow Corona Distance to project to one side, like +Z or -Z. Thank you.
In vray, Ambient Occlusion, it's possible with shadows turned off and object invisible.

[maru]

Sorry, but it's a bit too hard for me to imagine what exactly you are doing. Could you please add screenshots, renders?

[3daltm]

hi!
When I need to create dirt in a specific spot, ambient occlusion with an invisible object doesn't work. If I use Corona Distance with an invisible object, it works, but there's no option to create dirt only downwards; it does it on both sides.
thanks

[TomG]

You might be able to get something workable by applying the Distance Map version of the material to a Decal, and positioning it so that it takes effect where you want it. I tried somewhat ineffectively to soften the edges a bit too by reshaping the invisible object and using two other objects and an inverted distance map, much better results could be obtained with some actual care taken I wager :)

[maru]

Disabling the "visible to camera" option works, but the object still casts shadows. If it doesn't cast shadows, then it does not generate AO either. I am afraid this is impossible to do with Corona.

[3daltm]

thanks TomG.
This process is quite complex in large scenes. I just wanted it to work like in V-Ray, where you can turn off objects and shadows for objects used to create dirt. I hope it will be possible in the future. Thank you very much.

[3daltm]

i know Maru
but thanks.