Can I Cut A Door Through One Prim?

I'm trying to figure out how to cut a door through a wall without having to use 3 prims.

Can I cut a rectangular path through it and off-center it to form a doorway?

Thanks!

- Lenny

You can create a central rectangular door with one prim easily enough.

1. Make a wall panel.
2. Cut path to halve the prim (0.125 and 0.625)
3. Hollow the remaining prim with a rectangle

You can then change the aspect ratio of the prim to change the door shape, but you might not get exactly the result you are looking for.

RO

Thanks for the suggestion. I just tried but you're right, not really what I'm shooting for as the hollow still maintains a squarish rather than rectangular pattern. I am presently learning to script a sliding door and was hoping to have a doorway that didn't have to consist of two sides and an overhang.

Thanks though.

- Lenny

I think the ability to position or stretch a hole within a prim, independent of the shape of that prim, would be a useful new feature for us builders.

I wholeheartedly agree.

A two prim solution would be to path cut a quarter of the panel away, then reshape it in the X direction to get the door shape you are looking for, and then add another wall prim at the side. more flexible, but again it still might not get the right result.

A one prim wall with an arbitrarily shaped and positioned door is a good example of what can be done with a "geometric" sculpty, if you care to expand your skills beyond traditional prims.

That is an interesting idea but something tells me that I would not want to use sculpties for building structures tho - in times of lag they will just appear as balls..... and if you use a lot of them together, the lag becomes immense.

It would be useful, yes, of course. However, there's a good reason we can't do that. It would be computationally expensive, and challenging to implement.

The "hole" in a prim isn't actually a hole at all. The way prims are made is by extruding 2D shapes (profiles) along perpendicularly oriented 2D paths in 3D space. A sphere, for example, is made by extruding an arc profile along a circular path. A torus comes from extruding a circular profile along a circular path. A cube comes from extruding a rectangular profile along a rectangular path. A prism is a rectangular profile on a triangular path. Etc., etc., etc.

This is why holes can only exist on the Z axis. The path runs along the XY plane, and is intersected by Z. When you "increase the hole size", what you're actually doing is decreasing the size of the profile shape, to expose the pre-existing empty space inside the path shape. In actuality, that hole is always there, but when the profile is at its full size, it's perfectly positioned to obscure the hole from view. Changing the profile size to expose the hole is a very simple, one-step calculation.

"Moving" the hole, on the other hand, would be far more complicated. To move the hole, you'd need the profile's size to be different at every point along the path. That's a lot of extra computational overhead. It's of course nothing a computer can't handle with just one prim, but when you've got thousands of prims in a scene, it could add up. And that's before you even get into the impact it might have on physics.

That said, I suspect it probably wouldn't add up to the point that it would significantly impact anyone's frame rate, and the physics probably could be dealt with without breaking too much. I think the real reason the feature doesn't exist is not because the calculations themselves would be too hard for computers to perform, but because implementing the formulas for them would probably be such a pain in the ass that no Linden has thus far volunteered to tackle it. I'm not a programmer though, and I'm certainly not privy to the inner workings of the Linden mind, so take this theory for what it is, just a guess.

In any case, it is important to understand what you're looking at when you see those prim holes. They're not additive properties, as the in-world editor might imply. They're pre-existing, inherent features of he geometric process, exposed by subtraction, not by addition. That makes all the difference in the world for what they can and can't easily do.

This is a valid concern. But the issue of sculpties and lag is more complex than it is often made out to be. Ones made from an 8x8 bitmap (this is all that is needed for the wall with door) could and should produce less lag than a two-prim solution. Unfortunately, the current implementation of sculpties in the client expands this compact representation into a full size one by creating a ton of degenerate faces. Later in the processing pipeline, some of these seem to get eliminated, (My understanding is fuzzy here). The end result is that they are less lag-inducing than a full-sized sculpty, but more than they should be.

Handling small sculpties efficiently is on the roadmap for sculpty development. (It's one aspect of http://wiki.secondlife.com/wiki/Sculpted_Prim#Roadmap, VWR-1336). I think the main determiner of whether it gets done is how much demand there is for it.

Would it be as hard to implement a more custom prim option, or would that actually be easier? To me it sounds like they might be essentially the same...

When I say custom prim I don't mean a sculpty, still basic shapes, but more what you need when you need it. Such as just a simple rectangle with two of the corners cut into with circles (Best way I can think to explain... the shape needed to fill the end of the asian roof style that is two opposing quarter pipes)

This would be extrmeley useful as well.. to be able to draw a shape and make it into a prim, as long as you only used say a certain amount of points to create the shape, and chose what path it was created along (as you mentioned... rectangle, circle, triangle etc).

This could be a more accurate tool than sculpties in that it might possibly allow for more accurate movement into the object, as opposed to the bounding box of sculpties... disallow physical for the customs though as it would likely crash sims even faster than we can now.

Essentially an in-world tool for extremely simple sculpties, that actually allows the shape to be physically present, and not just shown (I mean the bounding box effect by that)

Hmm, if I'm reading you right, Okiphia, your idea is to enable the creation of custom profiles for extrusion along simple paths. That's an interesting idea. In theory, as long as the profiles are sufficiently simple (which you handled by saying "fixed number of points", the resulting objects would be pretty easy to handle, at least visually if not physically. Maybe physical behavior could be determined by the path shape. In other words, if it's a square path, the physics engine would treat it as a cube. If it's a round path, treat it as a cylinder or sphere.

As I said, I'm not a programmer, so I'm just making assumptions here. Maybe somebody more knowledgeable could think of more potential pitfalls. But in the absence of such information, I think it could work.

Cool idea. I think you should E-mail Qarl on this.

It seems like it should be very possible with simple profiles... but.. what's Qarl? =P

I'm still unsure on physicality though... giving it physical properties as just a square or something would probably also cause the same bounding box issues as normal sculpties have... which is something I'd hope to do away with on simple custom shapes if possible. Maybe not though.. I've no idea how it works either =P

Qarl's not a what; he's a who. Qarl Linden is the guy who created sculpties. He's usually a great one to talk to about new ideas like this, very responsive.


I'm not sure the physics problems can be dealt with very easily. For greatest efficiency, I'd assume the custom profiles would need to be a client side graphical effect, just like flexis and sculpties. And since physics happens on the server, there's no good way to get the physics to match the graphics. My understanding is that the server is too busy doing too many other things than to be concerned with customized shapes that it has no pre-programmed foreknowledge of.

Again, just to be clear though, I'm making assumptions here. I could certainly be wrong.

THankies ^^ I'll try contacting him ^^



The physics is one thing that I'm honestly worried about.. it's why I said make it not possible for the custom prims. If you have something too weird it might behave odd and crash the sim or something.. with custom shapes, disabling physics seems the best option..

But then still the bounding box..hmm...

Maybe an option to allow you to choose the shape at least of the bounding box, so that you don't just run into a box where there might be a curving piece.

Allow for some like.. pyramid, cube, sphere, half shpere, prism.. and whatnot.. maybe have the bounding box essentially prim-like itself, so that you can edit it some to match the shape at least a little. Running into bounding boxes where there is nothing is just annoying, and making it phantom as a whole can be bad, as maybe its a wall section or something.

hmm..so many variables to think about =P

once people started talking about 2d geometrical whosawatsits i phased out, it's cool you guys know that stuff tho.

if your door is on the bottom floor or there is wall below it, make a flat rectangle, cut the hole, sink it into the ground/wall bellow so the bottom part is hidden. it's simple and dosen't work in all situations but does the job

-Crunch

That's what the Torotoken (I think it's spelt like that) simple sculptie maker does. I made a 15 step staircase by setting the points in a diagonal zigzag at 45 degress, and leaving a flat back. I uploaded the texture and applied it to a stretched cube and extruded it out to about 1.5 m to give width to the staircase. Another prim was used to give a neater underside and, a non-phantom ramp (invisible face). Finished off with a side sloping side panel to conceal step ends and textured the stairs with planking stretched and positioned to emphasise the steppiness.
Quite good but it all looks a bit worn as sculpties are a bit irregular about the edges!

Yes.. it is what torotoken is used for.. but thats not what I was wondering is possible. I know it is possible with normal sculpties.. I've used torotoken as well as rokuro... but what I was wondering is if it is possible to implement a more basic version of it into SL itself to make 'pseudo-sculpted' prims. Simple outline (Maybe 12-15 points) extruded, maybe given an option of extrude or rotate, and have that be in-world.. would be invaluable, especially as no detail should be lost in the process (No upload.. not fine detail models anyway, but it won't be lumpy as non-lossless sculpties are...

But yes..that is the essential premise, torotoken simplified.. and shoved into SL I suppose lol.

I made a suggestion a few months back for an offset to the hollow. It is somewhere in the ether, but allowing hollow to be moved along the x or y planes would be nice. But if it is going to be this much trouble, it's just not worth it.

Okiphia, you could cut a hollow into a wall, and then use a second prim as a sliding door inside the hollow. Save one extra prim, but not two.