Object Subtraction

I wish we could intersect prims and then use one to "subtract" the volume from the other one.

Even if it were only implemented as an alpha subtraction (i.e. it would look like the prim is cutting the other one, though it is actually just invisible and phantom), that would be cool.

But really, full physical subtraction would be awesome.

Alpha subtraction won't work... or rather, it doesn't work, because you can already do this. When you cut a piece of a prim out, you create surfaces that can't be mimicked with a texture.

And while I'd love to see prims we could carve, I don't think we are ready for it tech-wise. The more corners you have on a prim, the heavier the burden id places on the engine. So maybe in time, but I wouldn't hold my breath.

Oh god, I would love this, even if the negative prims still had to be "counted" against prim limit restrictions for parcels, vehicles, etc.

Something like this can be done with two prims, now... if you're willing to work at it. Message me in game and I can take a swing at how.

However, true boolean operations are, well... nonexistant.

ah, yeah, I guess I can see how you could do with with two prims. I think that might be somewhat limited... but still... yer a clever guy.

This probably won't happen for a long time, if ever. It would AT LEAST require an upgrade to Havok 2, and even then it probably won't happen. The reason? LL's server code has physics code pre-programmed to handle certain shapes, and certain shapes only. Allowing object subtraction would result in non-standard physical shapes.

That isn't totaly true. Ever wonder how hollow is calculated? They subtract out the the center part. And when the hollow parts mass is greater then the shapes mass it doesn't subtract it out. Thats how they fixed negitive mass shapes.

Folks -

This has been brought up too many times for me to count; and I've only been on SL for a month!

For the record, I'm a long-time Level-Designer for games like Quake & Half-Life. Been doing it for over 10 years; so I know all about "Subtraction" and CSG techniques and vertex-editing and all of that. I worked at Sierra & WON.net for 3+ years, as well.

I would love to see these features in SL; but its not going to happen.

The problem is, we're playing an online game with objects that have to be transmitted in real-time. Sending every object's vertex over the 'net is time-consuming and bandwidth-consuming.

The compromise LL ended up with, is Prims. By having "pre-formatted" objects that we can modify in specific ways, ONLY those modification numbers need to be transmitted. This results in less data being transferred. It may not be a lot less - but when you're talking about having upwards of 100 to 1,000 people in an area at the same time, every little bit of optimization is important!

Yes they're imperfect, yes they can be a pain in the ass - however, they're better and more powerful than any other MMO's system!

Take care,

--Noel "HB" Wade
(Tread Whiplash)

P.S. The other thing about prims, is that they don't really have to do much "error-checking" to make sure someone hasn't created an impossible-to-render object with invalid vertices or other issues... Its also easier to control the overall graphic complexity of any given area with prims vs. arbitrary shapes - as prims have defined limits to the amount of vertices & level-of-detail they contain; whereas a given 3d Mesh imported into the game could have no limit to its size or complexity. So its more than just a bandwidth-issue.