Continuous Geometry: necessary or not?

[skogzort]

Hello,

I am working on my first Architectural rendering and I have a few basic questions about wall/floor geometry. I don’t want to go back and have to attach/weld stuff after I’m finished because of rendering artifacts, but I don’t want to do a lot of time consuming work ahead of time if it’s not necessary. So I would like to ask the people who have been using Vray: Does it work well with non-continuous geometry, or is it necessary to make everything one continuous mesh in order to get correct lighting/shadows with no artifacts?

More specifically:

1) Is it ok to “push-through” walls/roofs/floors so that the seams between them are not one continuous mesh?

2) If you can push through geometry, does it matter how far through you go? – In other words if you push one wall too far inside of another will it make it so that the shadows don’t line up correctly and the corner looks weird?

3) I know co-planner faces are not ok, but what about co-planar edges? Like if your using a single plane for a window and it’s borders end exactly where the frame begins?

4) This is more of a general geometry question: When using Vray is it ever necessary to “subdivide” the walls and floors to get accurate shadows and lighting? – so that there are more vertices per geometry for the rendering to work with – or is this not applicable when using Vray?

5) Finally – Does anyone know how MR in Max8/9 works with regard to these same questions?

Thanks very much for your time and info

[RErender]

While it always a good idea to model cleanly you should be all right with most of the above scenarios. Vray is way more adaptable than say Lightscape. Sometimes subdividing can help in the rare situation but mostly it is not necessary..

[joconnell]

Re: Continuous Geometry: necessary or not?

1) Is it ok to “push-through” walls/roofs/floors so that the seams between them are not one continuous mesh?


Yep.

2) If you can push through geometry, does it matter how far through you go? – In other words if you push one wall too far inside of another will it make it so that the shadows don’t line up correctly and the corner looks weird?


Nope.

3) I know co-planner faces are not ok, but what about co-planar edges? Like if your using a single plane for a window and it’s borders end exactly where the frame begins?


No problem with them at all - it's only co planar faces that causes problems for the raytracers. Edges dont take up any area.

4) This is more of a general geometry question: When using Vray is it ever necessary to “subdivide” the walls and floors to get accurate shadows and lighting? – so that there are more vertices per geometry for the rendering to work with – or is this not applicable when using Vray?

Nope - that's all to do with your sampling and nothing to do with your mesh density.

5) Finally – Does anyone know how MR in Max8/9 works with regard to these same questions?

Pretty much the exact same way - lightscape used to bake the lighting data into the mesh so its accuracy was based on mesh density and thus was way more snotty about the mesh you gave it. Vray and mr aren't.

[jujubee]

Sometimes there are issues where geometry intersects or overlaps. It's good practice to keep your:

\Global Switches\Raytracing\Secondary Bias\

set to 0.001

If you can't type in this value, set your Max preferences spinners precision decimal value to 5.

[priad]

did you speak about light leak juju?

[DaForce]

only problem with keeping it at 0.001 all the time is it can introduce rendering problems.. artifacts..etc..

IMO best to keep it at 0.0 unless you need to change it.
I would always recommend fixing the geometry above all tho.

[Pixelab]

Is it a problem to have hidden coplanar faces ? (& a 0.0 secondary ray biais)

Not hidden objects with coplanar faces, but for example, visible columns on a floor, with the under face (wich will never be seen) of the colum coplanar with the floor face.

[percydaman]

coplanar faces are fine IF, and thats a big IF, they aren't visible to the camera. Its better frankly to have hidden coplanar faces overlap, to be safe.

[Pixelab]

coplanar faces are fine IF, and thats a big IF, they aren't visible to the camera. Its better frankly to have hidden coplanar faces overlap, to be safe.

That's what I do, in a preventive way...

Now I know the truth

[skogzort]

Percydaman,

Does the distance of the overlap/push-through matter? I mean how far under the floor does the bottom of the pillar have to be before Vray no longer considers it coplanar?

[ene.xis]

Vray no longer considers it coplanar?

?
coplanar..means only one way?does it not?it either is in the same plane or ain t...or is it any diferent to vray?

[marco]

I think skogzort is asking: until what distance between 2 paralell planes VRay is considering them to be coplanar.....
Of course in reality its coplanar or not coplanar and nothing else, but since each software has a certain accuracy there will be a sort of "grey area".

does it happen to be system unit dependent ?

Marco

[DaForce]

Im pretty sure its either they are coplanar or they arnt.

2 faces take up the exact same space. If one face is down a mm they are no longer taking up the same space.