Fix ray tracing with XR and camera relative rendering

[fabien-unity]

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Purpose of this PR

Fix XR multi-pass and single-pass modes with ray tracing and camera relative rendering
Fix for https://fogbugz.unity3d.com/f/cases/1336608

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Testing status

Tested locally using template scene + ray-traced reflections and AO

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Comments to reviewers

I also tested the repro project from the ticket with 2020.3 to confirm it works, but the shaders have changed a bit and it will not be a straight backport.

[anisunity]

looks fine to me except for some indentation issues

[m0nsky]

Hi, sorry to bother. I've tested this locally and can confirm this fixes the issue, but you've forgotten to apply the same changes to RaytracingShadow.raytrace, after that it should be perfect. (Just did it manually and can confirm it will fix the RT shadows in XR)

Thanks for fixing my bugreport so quick, I appreciate it.

[fabien-unity]

@m0nsky ah good point! Thanks for reporting and following up. I'll add the code to the shadows tomorrow after some more testing.

[sebastienlagarde]

@anisunity / @fabien-unity by doing call like this we will always make mistake with copy/paste

As far as I can see the code is always the same. We should do a function and call it.

RayDesc rayDescriptor;
InitRayDesc(rayDescriptor, posInput.positionWS, normalData.normalWS, direction);

with

InitRayDesc(RayDesc rayDescriptor, ...)
{
rayDescriptor.Origin = ApplyCameraRelativeXR(posInput.positionWS + normalData.normalWS * _RaytracingRayBias);
rayDescriptor.Direction = direction.xyz;
rayDescriptor.TMin = 0.0;
rayDescriptor.TMax = _RaytracingRayMaxLength;
}

Thought?

[fabien-unity]

Yes that'll be ideal. I can refactor the code, unless @anisunity wants to do it :)

[anisunity]

i'll Do it. Does it have to be in this PR?

[anisunity]

@fabien-unity

[fabien-unity]

I'm ok with the refactor being done after this PR lands.

[sebastienlagarde]

alright, landing this PR then :)