A small bug in the pbrtdemoapp.

https://github.com/jbikker/lighthouse2/blob/a046e58b7d281885977c5e096c409926ebda829c/apps/pbrtdemoapp/main.cpp#L189-L190

I think this should be:

float3 camPos = renderer->GetCamera()->transform.GetTranslation();
float3 camDir = renderer->GetCamera()->transform.GetForward();