Big, smooth and round

[Kaluura Boa]

How to do that?

So, I'm making dirigibles (blimps, whatever, like the Hindenburg minus the fire hazards) and my problem is the land impact. I can do super-smooth round small objects but at the scale I need, all I get is big, smooth... and octogonal, or else the land impact turns into an extinction level event. (Land impact, crater, meteor, sorry...)

Hence the question: Is there a trick to make a huge spheroid (like 50x20x20m) which looks as smooth as a real prim but without the insane land impact? I'm talking only about the building part because I use a simple cube as physical shape and that's already more than I need.

 (Excuse me if I am not super clear but my blood pressure is hitting the roof and I am super close from the giga-rant about land impact.)

[Luc Starsider]

Either you are going to have to make the mesh very low poly and 'fake' detail with textures, or you could try to breake the mesh up into smaller pieces where the LOD kicks in at a closer distance. I think that should have an impact on LI. I'm no expert, so I could be wrong.

Either way, you are going to want to make your own LOD meshes.

- Luc -

[Rival Destiny]

Mega Mesh??

[Min Barzane]

when uploading input 0 on med,low and lowest LOD boxes and pick lowest on physiscs tab

[Thinkerer Melville]

You can make a single prim sphere of size up to 64m.  It may look octagonal with graphics set to low, but wil lbe a sphere in better quality graphics..  You can texture it as you please.

TKR 

 

[Kaluura Boa]

@Luc Starsider: Multiple meshes...That is something I have not tried yet. Starting Blender!

@Rival Destiny: Mega-meshes... Well, it is all relative since now prims can be up to 64x64x64.

@Min Barzane: I was about to say "No can do" but I will check the LOD formulas first. I already go without a real lowest LOD, maybe I can remove more.

@Thinkerer Melville: Thank you. You made me laugh. :smileyhappy: I really wish it was the problem... but my graphics are set beyond ultra, with shadows and everything.

 

[Drongle McMahon]

At that size (radius=28.5) the low and lowest LOD meshes have no effect at all on download weight. The effect of the medium is still appreciable, but less than you might expect. Using the same LOD meshes as the prim sphere, I got download weight (and LI) of 10.8 at that size. Using the high LOD mesh at all LODs gives 16, while using the lowest at all except high LOD gives 7.

This is probably one of those cases where a sculpty is difficult to beat (texturing and physics issues apart !!). There is no waste of triangles in a smooth shape like this. The simple sculpty sphere has more vertices and therefore has a smoother perimeter than the prim sphere. It has a download weight of 27, but its LI stays at 1.  Using the sculpty geometry as a mesh gives a download weight of 29. (Of course you can't link the sculpty or the prim sphere to any mesh without getting the LI increased to the download weight!).

If it's just a smooth spheroid, you could use the prim sphere. The sculpty will allow much more detailed shaping.

[Fluffy Sharkfin]

If you're looking for ways to optimize smooth, rounded objects then this info on Sphere Topology may be of interest to you.

[Chosen Few]

A few things to consider:

 

1.  Roundness

You may want to weigh the fact that real blimps are NOT round.  They are always faceted.  They're made by stretching a canvas material tightly over a rigid airframe scaffold.  Take a look at any photo of a real blimp, and you can clearly see the facets.  With that in mind, I'd forget all about "super-smooth", for this, if I were you (unless your goal is to be cartoony). 

You mentioned the Hindenburg, for example.  That ship was distinctly angular, not a single smooth curve on its entire body.  From photographs, it appears to have had about 24 sections around its circumference, and somewhere around 48 sections along its length.  There were probably more subsections in the airframe than that, but that's what was visible from the outside.

Whatever the actual number of facets was on the real thing, a convincing model can be made with relatively few.  Take a look at this rendering, for example:  http://www.cgmagic.de/getgalleryitem.asp-Dateien/Hindenburg.jpg   It appears to be only 24x20 facets, and it looks quite real (aside from the artist's strange choice of coloring it white instead of silver).

 

2.  Believability

If the real Hindenburg, which was 245M long, was structurally sound with only 24x48 visible facets, then a relatively minature 50M version would certainly be plausible with far fewer sections. In fact, it's likely it would NEED fewer sections, in order to keep the weight down.  The less volume there is for its lighter-than-air gasses, the less skeletal structure any airship can afford to have.

For a plausible model, you only need enough facets to suggest that the structure would be rigid enough to hold together against RL physical forces.

 

3.  Proportion

You said you wanted a length of 50M.  But you also said you wanted a diameter of 20. That's not in keeping with the proportions of real airships. Again, if the goal is to be cartoony, then go for it.  But if you want to be realistic, you'll need to slim it down.

The Hindenburg, at 245M long, had a diameter of about 41M.  Shrink it to a length of 50M, and you end up with a diameter of less than 10M.  That proportionality alone cuts your land impact considerably. 

Even a fatter ship like the Goodyear Blimp still isn't as fat as your suggested numbers.  If it were 50M long, its diameter would be only 14.5M.

 

 

I went ahead and replicated the main body of the Hindenburg model in that linked picture, just now.  I went with 24x20 sections for the high LOD, and 12x12 sections for the medium.  It looks more than smooth enough for believability.  At a length of 50M, I get a land impact of 17 (coming from the download weight).  Is 17 what you'd consider "extinction level"?.

If you absolutely must have the lowest land impact possible, then use a sculpty.  If you'd rather be more render-efficient, more realistic, and have better physics, I'd say 17 is hardly the end of the world.

 

[Cathy Foil]

Just a slight technical correction.

A "Blimp" has no solid inner structure to keep its shape.  It keeps it shape by gas pressure like a helium balloon.  Blimps are smooth and don't have facets.  What you may be interpreting as facets are seams of the material that covers the helium filled part of the ship so it is smooth.  The name "Blimp" comes from the sound the ship makes when you thump the side gas filled part with your finger which sounds like blimp. LOL

The Hindenburg was a "Dirigible" and has an inner framework construction which material is stretched over giving it the facets that Chosen talked about.

Chosen is right about everything else.  

I just happen to be a big airship fan. LOL 

[Chosen Few]

Thanks for the correction, Cathy.

I gladly bow to your superior knowledge of airships. I had no idea blimps are non-rigid.  I thought all airshops had frames.  I guess not.  After your post, I'm reading a little bit about the subject now, and it's quite interesting.

I'm delighted that word "blimp" is actually onomatopoeia.  I'm picturing what it must have been like for whoever discovered that sound first, and somehow it makes me smile.  I don't know why; I just really think it's cool.

[Karl Reisman]

it's impossible to get big smooth and round at the same time in Sl currently. pic two.  right now any.. any mesh over 20m in any direction, will cause a huge LI increase if the  mesh is "walkable" inside. there is currently a JIRA issue out there on this.  But basically nothing over 20M in any direction. right now, I know only of two makers on Sl making full scale zeppellins,  one of them is Cody007 Skytower, and he has a nice vicillian Zeppellin, that is walkable.|

Scott 

[Kaluura Boa]

@Fluffy Sharkfin: Thank you! The control freak in me is happy. :heart: Now, I spend hours arranging every triangle... but I like the result, especially when I play with some shine.

@Chosen Few: Realism... Hmmm... We're in SL and I'm building steampunk dirigibles. I think I threw realism out the window a few years ago. :smileywink: