The glass reflection detail problem.

[LudvikKoutny]

Hi,

first of all sorry for making yet another "Corona this, Corona that..." thread.

For past few months, I've been running around this forum randomly shouting that V-Ray is not good at rendering nice looking detailed glass, but I never actually took the time to sit down and do some objective comparisons, to back it up with some proof.

Now, that I am making assets for both renderers, I make scenes with goal to make them identical and when I stumbled across scene with glass, I am indeed observing some substantial differences between how V-Ray handles refractions and reflections under similar conditions. By similar conditions, I mean that my V-Ray material has reflect on backside enabled, and I have global trace depth override enabled and set to 25.

Despite backside reflections being enabled and trace depth set to same number, V-Ray still seems to miss a lot of fine detail reflections, and that's probably the detail I am missing in my glass materials in V-Ray.

Here's a picture to demonstrate it. Top one is Corona, bottom one is V-Ray, and bottom row is always Corona on the left and V-Ray on the right.


I can of course provide scene if necessary.

Thanks

[vlado]

Did you also set the cut-off in your glass materials to 0.0?

Best regards,
Vlado

[LudvikKoutny]

Yep, I've tried it, and it had no effect so I returned the value back to 0.001.

I tried to do it again just now to make 100% sure, but it indeed doesn't make much (if any) difference:

[vlado]

Then you can post the scene if you like... it's very hard for me to a) notice the differences (they are quite subtle) and b) say what causes them, just from the images. It looks like some of the differences are just noise or slightly different bump.

Best regards,
Vlado

[LudvikKoutny]

Wow, you are right! It was just different bump all along I take it all back then. Once bump is removed, there is almost no difference.


I stand corrected

[vlado]

Aha, good That's remarkable parity between the outputs from the two engines though... I like that fact

Best regards,
Vlado

[LudvikKoutny]

Yep. So the glass quality myth can be put to rest finally.

I've made a few more tests in more synthetic conditions to verify the results, and while there are some differences, they are very minor. If anything, V-Ray seems to render noise free glass a bit faster.