The Slice must flow

So cubes have these parameters called Slice Begin and Slice End. They allow you to reduce the height (z scale) of the prim without actually altering the value. This can be very handy since it does not affect other parameters like taper, top shear, twist or even texture scale/repeats.

But wouldn't it be even better of we would have this same functionality for the other dimensions of the prim? This could open up a lot of new possible shapes when combined with the hollow and path cut parameters. I searched through the JIRA and didn't immediately find anything referencing this... do you guys feel this has merit enough to make a feature suggestion?

LOL.... I'm still getting used to having slice at all. It is a way cool function, I agree. I guess I can always imagine a boatload of things that I could do .... if only SL offered yet another function. For right now, I wouldn't kick if they decided to make more of them happen, but I'm not going to worry if it takes a while.

Great thread title!

What ever happened to Slice, anyway? Is it still on the market? I don't think I've seen a can or bottle of it in years. Did the Spacing Guild drink it all?


Anyway, regarding the actual topic at hand, while I'm sure there's no one who would disagree that it would be useful to be able to slice a prim on any axis, the reality is that that sort of thing is much easier talked about than implemented. Just as with hollows, cuts, etc., it's not a simple request to be able to do all things on all axes. This is because of the way in which prims are constructed.

You see, prims are not quite the mundane geometric forms they appear to be at first glance. Each one is actually a revolve. They're created by extruding or "sweeping" a 2D shape, called a profile, along or around another, perpendicular, 2D shape, called a path.

The cube is made from a rectangular profile, extruded along a straight path. The cylinder is likewise created by extruding a circular profile along a straight path. A prism (non-tapered) is simply a triangular profile, again extruded along a straight path. The sphere is where we start getting into a slightly more complex arrangement, a circular path instead of a straight one. The sphere is created by sweeping an arc-shaped profile around a circle-shaped path. To complete the list, a torus is a circular profile swept around a circular path, a tube is a rectangular profile swept around a circular path, and a ring is a triangular profile swept around a circular path.

All of the edits we make to prim shapes, including slicing, involve making simple alterations to either the profile shape or the path shape. In order to make a slice or a hollow happen on any axis besides the ones they're already fixed to, the profile would have to change dynamically at each point along the path, and in some rather extreme ways at certain points. Either that, or make the path axis movable. Neither is impossible, of course, but either would add several more layers of complexity to the existing mathematics behind prims. It's a tall order, in terms of labor. Given the choice, I'd much rather the LL graphics team focus their limited manpower on frying MUCH bigger fish, like mesh support, better lighting, a proper material/shader system, etc., than spend any time at all trying to radically improve prims. If there's time to rewrite the prim system when all that other stuff is done, great. But if not, I won't be too broken up about it.

there is a jira on the topic somewhere... I do remember it

personally I think the physics engine would choke and die the first time you hollowed a cylinder and sliced it on the y axis to .49/.51 producing 2 separate rectangular prims.

interesting footnote:
we've always had the ability to slice cubes, it was only via script originally, and now it's only via edit.

Actually, it always could be done via edit, just a little less directly than how we can do it now. Slice on a cube or cylinder is the same parameter as Dimple on a sphere. So previously, the way to do a slice was to start by dimpling a sphere, and then convert it to a cube.

good point, I should've said directly, but really I guess it doesn't matter. I'm still very annoyed it's no longer accessible by script.

If you think about how prims are made, you'd have to create a new profile. The problem is that wouldn't produce the effect you want from the texture map.

By the way, slice *is* path cut for cubes, but the same parameter does a profile cut for spheres.

I would like to get some additional features for parametric prims, too, if they're not going to provide in-world mesh editing. In-world editing is a valuable feature of SL, and it's becoming increasingly sidelined.

Ah, I understand now. Before this thread, I had no real idea how prims were constructed at an atomic level. I now see what you guys mean and agree, it would be a monumental effort and probably not a good allocation of manpower when there are much bigger fish to fry presently.

Thanks for the cool explanations!
(and I'm glad the pun was appreciated! I just recently watched the movie)

We've had this discussion before, and as you know, I strongly disagree.

Yes, in-world editing is a valuable feature of SL. On that, we do agree, wholeheartedly. The ability to edit what has always been editable will never go away. So that value will always remain. It's not being sidelined in any way. SL is simply gaining new abilities to import other types of content, in addition to, not instead of, the kind it's always been able to use all along.

For every person who boo-hoo's over the fact that they'll actually have to LEARN something if they want to be able to make some of these new types of content, there's someone else who rejoices over the very same fact that they won't have to learn anything new at all, since they'll be able to keep right on using tools that they already know.

As with anything else, when meshes arrive, those who are not already skilled with any external modeling program will need to learn to use one if they want to be able to make meshes, while those who already have that skill won't have much new learning to do at all, beyond the specific rules and quirks that SL will impose, just like every platform does. I fail to see why that's such a big deal.

Want to know what would happen if there were an in-world mesh editor? The same exact thing. Those who are predisposed to be good at modeling, whether it be through experience or just plain instinct, would do well with it in a relatively short time, while those who don't have a natural affinity would be faced with a steeper learning curve, and would have to put in more active brain power in the beginning. But at the end of the day, anyone and everyone who wants to do it would be just as capable as everyone else. That's just the nature of a skill, every skill.

It's worth keeping in mind that we've never ever had the in-world ability to edit textures, sounds, or animations, and nobody seems to complain about that. Sculpties and meshes are no different. Advanced content demands advanced tools.

The viewer cannot and should not be expected to do everything 3D, any more than a Web browser can or should be expected to create every last kind of Internet content. There's a reason it's called "viewer", as opposed to "modeler" or "animator" or "painter".

But again, we've been around this carousel a hundred times. Bottom line, it is what it is.

Path cut is a Profile Cut on prisms, blocks, and cylinders (the linear prims). The path of the cube is the straight line that the triangular, square, or round profile takes along the Z axis. Think about it.

It's a Path Cut. It shortens the length of the path the profile takes as it follows the Z axis.

OK, but please try and pay attention to what my argument is instead of trivializing it as "it's too hard". It's not that *creating* stuff is too hard, it's that once it's created, it's effectively no-mod. It's a one-way trip.

You say it's not, but the difference between modding something made of prims and sculpts is huge. You can't just move parts around, you have to start from scratch (or use a ripping tool to illegally clone the sculpt map, but that's not cricket). Oh, it's easy enough to replicate simple sculpts, but anything done with any precision is near enough to impossible.

Also, the viewer is not just a web browser. It's an editor as well.

::raises hand::
I've complained about the lack of abilty to edit animations, specifically loop and priority, repeatedly. some trivial resize code for images wouldn't hurt either, and the ability to trim sounds be nice..... =)

I do agree that mesh editing is probably a bit complex to ask for in SL.

I never said anything about anything being "too hard". I get your point about the modifications, but again, the same has always been true of textures, animations, and sounds. Not everything can be modifiable.




Again, anyone who wants to learn to make sculpts can. There are literally dozens of tools available, many of which are free.

Modding existing sculpts is a different story, sure. But where is it written that being able to mod everything is a necessity for a good virtual world? Some might argue that it is, but just as many would argue just as passionately that it isn't. It makes for worthwhile debate, certainly. But again, at the end of the day, it is what it is.




A browser likewise does more than just browse. Simple content can be edited with a browser, which is why we're able to communicate through this forum. But rich content must be created with more powerful tools, as we've discussed many times before.

OK, somebody's complained.

I am not finding that animation useful in understanding how prims work.

Anyone know of any other animations designed to explain how prims work?

There's a lot of content creation systems, such as Aviary, that work in browsers, and the role of the web browser seems to be growing.

The one thing to keep in mind when doing a slice, is that the overall size of the object will still show on the map and the centerpoint is still based on the true center of the original whole. Not sure how much that may or many not impact things, but it can look odd on a mini map that ends up showing your object way out on someone else's land.

I'm deleting this post, because it contained information that was most likely incorrect.

Only for spheres, rings, tubes, and toruses. For the linear prims the path is a straight line along the Z axis. The block is not a solid of revolution. The prism isn't a solid of revolution, it can't be. The cylinder COULD be a solid of revolution, but it isn't.

The linear prims are the ones you can make flexy. The flex works by modifying the path, before the prim is actually generated from it... the path flexes, and the profile is carried side to side with it.

You need to actually go in world and play with the different kinds of prims and see how they work. Try it.

Your animation is wrong. The base is the profile, the path is the vertical axis. Here's how they really work:



From: http://www.realityprime.com/articles/how-sl-primitives-really-work

The parameters are simply MISNAMED in the editor. That's all.

After a massive edit:

I read the article mentioned above and i went to SL and played a bit ...
Let me introduce SL-path , SL-slice and SL-profile to describe what i see in the SL-viewer, while i use path and profile when i refer to the article above. I hope that makes sense.

for Box, Cylinder and Prism:

The SL-path seems to lay in the xy-plane and have rectangular shape. The slicing goes along the z-axis. But according to the article above it should be opposite: The path should go along the z-axis and the profile should lay in the xy-plane. So the translation is:

SL-path == profile
SL-Slice == path


For Sphere:

I have no idea what the cause is, but the Sphere poles are on the sides not at bottom and top. I rotate the sphere along the y-axis by 90 degree for better comparison (i am not sure if this is correct as i do not know why the sphere is rezzed in that way): So after rotating the prim the SL-path lies in the XY-plane and has circular shape. The SL-dimple runs along the z-axis. Again the comparison with the mentioned article above gives:

SL-Path == profile
SL-Dimple == ?

For me dimple does something different than i expect from a pathcut so what is it at the end ?


For Torus, Tube, Ring:

The rotation issue is like with the Sphere. So again i rotate the object along the y-axis by 90 degrees and then: The SL-Path now is in the xy-plane

SL-PATH == path
SL-Profile == profile

Is this a correct analysis of what is going on ?

Upon further reflection, I'm now inclined to believe that Argent's explanation is correct. The "Path Cut" parameter, for cubes and cylinders is indeed mislabeled. It's actually a profile cut. My thanks to those who offered polite corrections to my misinformation, and my apologies if my earlier comments caused anyone any undue confusion.

I've edited my posts throughout this thread to omit any incorrect facts.

The reason the sphere, torus, ring, and tube lie "on their side" when you set rotation to <0,0,0>, is because they internally the "profile" is always "xy" and the "path" always starts in "Z". For the torus, ring, and tube what you have is basically a cylinder, prism, and block with the path bent around into a circle. For the sphere, the profile is a semicircle and the path is a degenerate circle wrapped into a point.

This isn't the only "oops" in the prim parameters. There's a worse one for rotation of child prims.