The Nissan looks pretty good but I think the texture of the glass ridges is doing a lot of work to sell it. The 190E looks only OK though. Compare it to the real thing (yes its not the exact same model, but the only difference should be the yellow bulb on the interior lamp)
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There's just so much more depth and subtley of material. In the Forza model its like a single surface behind the lens making the whole thing look rather flat. I'm not saying its terrible, but it's not quite right either. There's still something off about how the engine renders chrome too. It's like too perfect of a mirror. Because many headlights have chrome housings, I think this might be a big part of the problem, there is no amount of light diffusion, its either full highlight or full shadow. The chrome weirdness may also be a result of the cube map reflections being not quite geometrically correct, though I'm still not clear on what is being ray traced and what is not. But getting back to the images above, the grill in the picture of the real 190e has some softness in the reflections, whereas the Forza chrome is
extremely sharp which often on Forza surfaces tends to look artificial.
Anyways, it seems like they've definitely made some strides in paint rendering, but it seems like the FM23 engine carries over a lot from previous titles.