Closing Meshes

Benton

Hey guys,

Why do people demand that meshes are closed. For a community game project I modelled a toilet and the bottom of the toilet was not closed, because it would add on about 15 tris, and nobody would see that because the bottom of the toilet would be resting on the floor. But the other artists told me to close the mesh. Why is that?

SkyWay

Because...I can't think of a reason. Maybe they want to use the toilet as a physical object that could fly around the place...

Sorry, you'd be better off asking the other artists for a reason, see if they can provide a plausible explanation instead of a
"cause we say so"

Ace-Angel

Some engines don't like 'open' meshes since they add to vert count considerably more then a closed mesh.

There is also the issue of lightmap baking with closed mesh = more optimized and less mitigation to other surfaces, and etc...

Benton

Thanks guys. We are not using any light mapping, and the toilet is static, so I was thinking leaving meshes open was just frowned on. I will have to ask our art lead. Thanks

DeadlyFreeze

Why would it add more verts on a open edge?

I mean a box with an open face is 8 verts, a box completely closed is still 8 verts.

Jay Evans

if you don't close it the poop will fall out the bottom.

cryrid

I recall some engines/shadowing (stencil?) requiring closed volumes to get the best effect.

Moosey_G

It really depends, it could be for any number of reasons not the least of which is "just because." The best course of action would be to ask the people demanding why.

SkyWay

Ace-Angel wrote: »

Some engines don't like 'open' meshes since they add to vert count considerably more then a closed mesh.

There is also the issue of lightmap baking with closed mesh = more optimized and less mitigation to other surfaces, and etc...

I understand the lightmapping part...but open meshes add to the vertex count more than closed? I really thought it would be closed meshes that would have more vertices due to vertex-splitting when handling faces/smoothing groups O__o

I'll go with the poop falling out...yeah...that sounds just fine.

Eric Chadwick

Some older shadow-rendering systems required closed meshes. Also called watertight. 3d printers require closed meshes too.

Computron

Jay Evans wrote: »

if you don't close it the poop will fall out the bottom.

The only correct answer.

Benton

haha thanks guys

passerby

SkyWay wrote: »

I understand the lightmapping part...but open meshes add to the vertex count more than closed? I really thought it would be closed meshes that would have more vertices due to vertex-splitting when handling faces/smoothing groups O__o

I'll go with the poop falling out...yeah...that sounds just fine.

deleting faces wouldn't cause verts to be split due to smoothing groups.

if a face was set on a new SG it would since all the verts around that face would need 2 vertex normals to display the split in shading, but in the case of a face not being there, the border verts would only need 1 vertex normal each so wouldn't be split.

@Benton if they really demand you keep the mesh closed, i would map the faces that would always be hidden like the bottom of the toilet to something with a similar material on the toilet, or scale it;s uv island down. no sense wasting precious texture space on something that will never be seen.

sprunghunt

what if a level builder wants to put the toilet in upside down? perhaps you have a bathroom with several toilets with one of them broken.

Meshes should almost always be closed. It's just more useful to the Level designer/level builder that way.