Value set for the InstanceID() intrinsics

Hi,

I am probably missing something simple but is there a way to know what value unity passed to the system inside RayTracingAccelerationStructure.AddInstance for what becomes the InstanceID() shader code intrinsics value?

I understand InstanceID() to be a user defined id so I expected to be able to set it myself in AddInstance, or perhaps have AddInstance tell me what it set... it didn't seem to be the call order.

I need to know on the C# side so I can setup lookup tables indexable by InstanceID() in shader. As a temporary workaround I am doing a cumbersome id resolve pass that allows me to read those ids back for all the objects I have.

 

Hi,

Thanks for the confirmation. For the current version, in the context of quick testing if the id allocation algorithm currently used internally is simple enough and predictable, just being able to reproduce it in user code to mirror the id allocation sequence would still be quite helpful, even if temporary.

For making it configurable, what you said sounds good. Setting separately anytime sure sounds flexible but I don't know what the implications are for you... personally for now I don't plan to change the id I pass to a newly added instance...

By the way thanks a lot for the BuiltInRP sample you posted in another thread, it has been really helpful.