Combining HDRI lighting and closed space reflections in Octane Render

[Youndected1]

Hi, is there a way in Octane to have a car inside a tunnel still reflect the HDRI environment, while also receiving shadows and reflections from the tunnel itself? Maybe by using light linking, mixing shaders, or setting the tunnel to be invisible to reflections but still visible to rays?

[skientia]

The "best method" is subjective as it highly depends on 1. the level of simplicity, 2. expectations and 3. technical requirements.

Render layers and post-compositing are also two drastically different and viable paths.

One potential and relatively straightforward solution that wasn't cited (or may be implied at the end) is Ray Switch, here demonstrated at 0.5 [Reflection]:

[Youndected1]

The "best method" is subjective as it highly depends on 1. the level of simplicity, 2. expectations and 3. technical requirements.

Render layers and post-compositing are also two drastically different and viable paths.

One potential and relatively straightforward solution that wasn't cited (or may be implied at the end) is Ray Switchgunspin, here demonstrated at 0.5 [Reflection]:
ray-switch-env-tunnel-car-demo.jpg

I’m trying to keep the natural HDRI lighting for reflections on the car surface, but the tunnel geometry seems to override that. Has anyone managed a clean workaround without losing realism?

[skientia]

Has anyone managed a clean workaround without losing realism?

It's not plausible ("realistic") to begin with.
The tunnel, unless see-through (glass) is an obstruction to what's outside of it (street lights, sky, sun, moon reflection, and so forth).

The most control and likely most suited ("best") solution in such situation is compositing but requires the necessary competence.
Octane has its own built-in AOV compositor which should be sufficient.

Is the objective to simply obtain a plausible results similar to automotive ads or F1 clips or "cheating" (breaking rules) for "creative reasons"?
An explicit visual example is welcome.

[skientia]

I'm trying to keep the natural HDRI lighting for reflections on the car surface, but the tunnel geometry seems to override that.

The Ray Switch slider in question was set to .5, one could think of it as "50% opacity", if at maximum value (0-1) the result is either tunnel reflection or HDRI reflection, not a mix of the two as in the provided example.