Mesh turns Phantom in-world.

[SabbaSerenity]

Hi all,I'm just learning to build mesh using Sketch Up. (Not one of the best to use,I know)...But my problem is,I'm not sure what settings to use to import into SL.I can import stuff ok,but when it rezzes up,it is always phantom and I can never use the stairs.There's like an invisible wall stopping me.Is it LOD settings? Physics? I have no clue.And I can't seem to get to the Aditi site to try out a temp version before importing.

Any help is much appreciated.

Many thanks

Sabba.

[Rolig Loon]

If there's an invisible wall stopping you, then your mesh is non-phantom there.You need to do two things.  First, create and import a physics model that defines exactly where the non-phantom portions of your model should be --- the walking surface of your stairs, for example.  Then, having imported the model and the accompanying physics model, set the physics type (in yourBuild/Edit tool's Features tab) to Prim rather than the default Convex Hull.  If you've done it properly, you should find that the right parts of the model are non-phantom while the rest is phantom.  Take a look at some of the video tutorials on the Machinimatrix site.

[Aquila Kytori]

hi

As Rolig has already said you need to make a seperate mesh for your stairs Physics and upload that along with your actual stairs mesh. Have a look at this thread : http://community.secondlife.com/t5/Mesh/Problem-with-home-mesh/td-p/1786891

its for steps but may be helpfull with stairs aswell lol .

 

[SabbaSerenity]

Hi Rolig,I really didn't make myself clear..I can either walk thru my entire build   (Phantom) or.Walk around the building but not get thru doors and walk up stairs and stuff. (Non Phantom).

I'm thinking you are right!.Sketch up is just what is sez!.For sketching.I can draw amazing Architecture!.Hope I can get to grips with Blender easy enuff.lol.Thanks again for all your advice. it's much appreciated hun.Love and Kudos.

[SabbaSerenity]

Hi Aquila.I'm thinking I need to study more,and believe friends less when it come to building.

You were helpfull with your link.I really appreciated it.

ty.I'll look for your advice in future.

Love and respect.

Sabba.

 

[Rolig Loon]

Oh, that's not a mesh problem.  If you link a phantom prim to anything, the entire link set becomes phantom.  It's all or nothing.  If you have designed your mesh doorways and stairs correctly, though, they don't need to be phantom.  The mesh physics you have assigned to them should define which surfaces you are going to collide with and which ones are not collision surfaces.

[Zann Canto]

I have just started to learn Blender the last couple of weeks. I have the same problem described in this thread. My brick house is partly solid and partly phantom. Some things, such as windows, that should be open act solid; and some things that should be solid, such as walls, behave in a phantom fashion. I checked the "Features" tab to make sure the "Physics Shape Type" is prim, and it is. The structure is not linked to any phantom item -- and anyhow, that would not account for open spaces acting solid.

I'm wondering if my structure is improperly built. But perhaps I don't understand how to build and import a physics model of the item. Or is there something else I'm missing?

[Rolig Loon]

When you created your physics model, did you remember to leave openings in it for windows and doors?

[Zann Canto]

Yes, I decided to only leave openings for doors on my second try. But I must be doing something wrong in the physics setting or something else, because the results are the same. I can walk through the doors with only minor resistance, but I can also walk through the area beside the doors. Most of the walls seem fairly sound.

[Drongle McMahon]

Is the bounding box of your physics shape mesh the same as that of the high LOD mesh? If not, it gets stretched (or squashed) until it is, in each direction, xyz..

[Zann Canto]

Thanks! I double checked that and it was OK. I got to wondering if my physical model had become corrupted or just had bad settings due to my experimenting, so I created a new phyics model, and the doors worked better. However, I discovered that, although I could not walk *in* throught the walls, I could walk *out* through them. So I added a solidify modifier to my physics model, and it seems to work fine now. Does that make any sense?

[Drongle McMahon]

Depends to some extent on whether you are using triangle-based (no Analyze) or hull-based (Analyze) shapes. In fact both can be penetrated occasionally, more easily the higher the speed you collide with them. If you use thick shapes, then for hulls (Analyzed) you are unlikely to get through and the physics engine pushes you back out. For triangle-based shapes, if you penetrate the first surface you can get stuck between them! Also, you need to remove the edges of thickened triangle-based shapes because the narrow triangles escalate physics weight horribly. Often triangle-based walls are the cheaper option for physics weight, although their weights are very unpredictable (depend on triangle and vertex order in the dae file). However, hull-based shapes may perform better. To get the best control of the hull-based shapes, and lowest weights, make the shape up entirely of separate non-overlapping convex shapes - so the result is exactly what you provide, with no changes to eliminate concavities. Make the distaces between the parts very small to avoid leaky joints. Of course this is more work than letting the Analyze function do it for you. So if you get acceptable weights that way, there's no need to worry.

ETA - For some reason, triangle-based shapes seem to be more easily prnrtrated from the "back" - i.e. the side opposite where the normal sticks out, that doesn't get textured. I was never able to analyze that effect in detail, but it might explain some of the inside/outside differences (if you are using triangle-based shapes).

[Zann Canto]

Since I've been learning Blender for just 2 weeks, I know so little about what I'm doing that it is difficult for me to reply intelligently. However, I can tell you that my structure is made out of a cube, with the interior formed out of flipped duplicates of the walls. The windows and doors are cut out by subdividing and removing parts of the walls. I did not analyze this last upload, and the view in the virtual world I'm working in (3rd Rock Grid) looks like a bunch of triangles, so I'm guessing it's triangle based. 

The physics model of the structure is very simple with only 2 spaces for doors removed from floor to ceiling. I made separate pieces for the second story gables. It sounds like it  would be better to make flipped duplicates of the walls than to "solidify" them. I will try that.

Right now I'm building on my own islands (I can afford that on this grid), and upload is free, so I can experiment a lot. Although wasn't thinking much about the physics weight initially, I want to learn to do this right if I'm learning it at all. Thank you very much for your advice!

[Aquila Kytori]

hi

A couple of images to illustrate some of  what Drongle has already explained

A simple way to create a physics shape is to make a copy of the mesh on a separate layer in Blender and work on that to create either a Triangle based or a Box (Hull) based mesh.

The box method is very much like using prims in SL, replace all walls and floors etc with, ideally  rectangular box shapes. (the roof in this example is a solid triangle) . This  mesh  will need to be Analyzed in the uploader. Analyzed means that the uploader will try to divide your Physics mesh into a number of Hulls (box shapes) that will act as collision shapes once rezzed inworld. So if you have already used clearly defined box shapes in your Physics mesh  the uploader will recognize them as such and you will have a physics shape exactly as you have designed it .

 

Once you have rezzed your building inworld you can see the actual physics shape by going to the Develop menu

Develop > Render Metadata > Physics Shapes . The physics shapes will show (should show) in blue. Enabling  Show Physics is a good way of seeing an problem areas in your Physics shape.

Note : In the image below the Physics Type of the little house has been set to Physics type : Prim in the SL edit panel.

If left at the default Convex Hull you will see that there is no opening for the door.

 

If your mesh is a single Object in Blender then your physics mesh should also be a single Object before exporting.

I have uploade the .blend file to here :

http://www.pasteall.org/blend/26201

The Simple House mesh is on layer 1 and the different Physics meshes on the layers below .

[Drongle McMahon]

Ah! If you aren't on a Linden grid, then everything I said about physics could be wrong. The physics is done entirely on the server, and the server code of the LL servers is not open source. So there are certain to be differences with other grids. In fact they may even use different (versions of) physics engines.

[ObviousAltIsObvious]

http://lists.berlios.de/pipermail/opensim-users/2013-February/011702.html

 

[Zann Canto]

Thank you! I haven't seen many references to Open Sim grids and mesh, so I had assumed meshes in 3rd Rock Grid functioned much like they do in SL. It's good to know they may not always do so.

My building is working perfectly now, so I think the SL-based info has still proven useful. Zann

[Zann Canto]

Thank you immensely! Your post certainly proves the adage that a picture is worth a thousand words. Zann