Vray rendering polygons smooth, different closed mesh types

The design of my jewellery is heavily faceted but in some cases the vray render smooths the edges even though both elements are closed mesh and clearly faceted. i cant seem to find an answer for this anywhere.
As seen on the image below there are 2 shapes both faceted the left one renders as modeled but the right one renders with no edges… it’s in the same view with same materials. the only difference is i dont know where the left side element was originally modelled in.
basically if i have a mesh and reduce to show more polygons why would these not show in a render?

i think i found by chance the unweld feature, but if anyone can confirm thats also great

The mesh with control points enabled on the right looks like it has been welded completely. You can see that because the shading over the faces changes smoothly. Compare to the faces of the gems on the left.

The unweld feature is indeedwhat you need.

Thanks, any idea why using the union it adds extra vertices?

That is what a union does. Search for intersecting faces and add vertices, edges and faces where necessary to maintain the outer shell of the union. Likewise any parts that ended up inside have been removed.

thanks, guess this isn’t essential for me so i’ll just join

Note that if you use a glass/diamond type material you may get unwanted effects when internal geometry exists. You’ll be the best judge on what works for you, of course (:

yep, as yet i’m just on solids
I’ve been using HDRI for the lighting/env which is great for most shapes… but i have now one which is impossible to get right… also a slight angle change on camera completely alters the look which to me doesn’t make sense as i have to make more adjustments…