the old scene, tested vray settings - that's now the corona.
most problem was the glass, resulting in:
is a single-layer ground,
material twosided,
refraction color light grey (180)
object properties - uncheck cast shadows.
on rendering speed, there is no difference, is there glass or not.
but the glass can be seen in the picture.
1) corona clear render without photoshop
2) v-ray with photoshop
3) corona with photoshop - corrected color and sharp
