I find a new Vray shader recently, the “vraydirt”(it also known as a AO shader in Vray) shader. And I make a render test with share some tips here, hope it helps.
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This is the result before applying “vraydirt” shader, it looks shadow-less and weight-less.
This is the result after applying “vraydirt” shader, it looks more real form previous one and rendering very fast. It looks like a little “3S” effects, but I’m still hard to make a good 3S control from Vray.
The final results, I applying reflective materials and adjusting glossiness values. The rendering speed is slowing down however with a very well result, we can try more values between the speed and quality.