Okay, after playing around with the materials/render system I was using, I just could not get it to produce an image that looked like the Verdant sample picture, so I switched to a different system. I've done this with the PBR system (Physical Based Render) which has pre-calculated lights, materials and render engine. They're designed to more closely approximate the way real-world lights and shadows work, but the downside is they take longer to render because the 'rules' are more complex.
The other downside is non-PBR materials under PBR lighting look either too bright or flat; lacking contrast, so I have to create new PBR materials. I did that for the Verdant paint and silver wheel paint, but everything else is non-PBR.
I replaced the 4 ceiling lights with 4 PBR lights, and one of the things you'll notice is the difference in shadows.
Here's the reference photo of the planform in Verdant that I used to sample the color from,
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and here's what the paint color shader looks like that I created as a PBR shader based on samples from the Verdant planform photo.
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For reference, here's a snapshot of the car in the old Verdant shader with the non-PBR system for comparison.
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Here's the same shot with the PBR system. You can see the difference in shadow detail and accuracy, especially underneath the car (there are 4 overhead can lights).
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These new PBR renders are probably closer to the way the car is actually going to look in Dark Verdant, based on the photo of the planform. HOWEVER, one thing to remember is the planforms are only a few inches across, so the transitions from light to dark are very fast. There's a big difference in the transition from light to dark across a 4 inch curved surface, compared to a curved surface that's 4 feet long. Plus, these are just color shift surfaces. I haven't figured out yet how to get a metallic effect in a PBR material. I haven't worked with this system before because I didn't want the longer render times, but in this case it seems necessary to try and get closer to the way these metallics are going to look on the car.
Now to get busy creating new PBR materials to replace the old ones.