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learning mesh upload. Question


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As a practice I uploaded a simple mesh item: A cube with 2 missing faces so I can walk in. I want the faces to be solid but to be able to walk in it. Right now the best I get is a phantom like object I can walk through. anyone know what I could do to achieve what I want instead?

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If you want the cube to look solid but have two faces you can walk through, you'll need to make a physics mesh for your cube.

Easiest way? Delete the two faces you want to be phantom, save the altered mesh as your physics shape. In the upload floater, select this as your physics shape and don't click analyze. That should do the trick for you.

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Brief introductory guide...
You need a phsyics shape other than the default convex hull. You can choose either of two types, triangle-based (3) or hull-based (4)....
1. Your simple opened cube. (Backface culling on to see invisibility of backfaces).
2. Select all and use Mesh->Faces->Solidify to make inner surfaces.
3. Remove narrow edges, for triangle-based phsyics mesh. DON'T "Analyze".
4. Matching mesh made with simple non-overlapping pieces for hull-based physics mesh. DO "Analyze".
5. Use 2 for visible meshes and 3 or 4 for physics mesh. Set physics shape typem to "Prim" inworld.


Notes - The physics mesh is added on the Physics tab of the uploader - the "Anaylze" button is there too - the physics shape type is set on the Features tab of the inworld edit dialog - Use Mesh->Vertices->Separate->Selection to make the cubes separate objects - select and export each using SL preset, with "Selection Only" checked.

ETA - there are a million threads in this forum about physics shapes, with whatever level of technical detail you like.

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Hi and thanks for your help


I'm still working on this and I must admit I didn't see much progress. I'm trying again with something even more simple: 6 cubes.



I also have another cube I use for my physic shape.


Once in the mesh upload window I do the following:

Under Level of Detail: I chose high.

Under Physics: At setp 1 I chose "From File" and I then chose my simple cube I want to use as physic.

                          At step 2 I chose solid and I analyze

                          At step 3 I chose "Retain%", I then chose the retain 100 for retain 1 and I click on simplify.


I then click on calculate weight & fee and I am given a LI of 3.5



I noticed if I skipt he physic step I get 3.5 LI as well. If under the level of detail I chose lowest instead of High, I still get a LI of 3.5. So does not look like I'm getting much improvements here.

Any thought about what I might be doing wrong?

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I'm guessing that your 6 cubes are 6 separate Objects in Blender which will give a LI if 3.0 ( 0.5 server weight x 6 ) and you have exported and uploaded that Physics cube aswell because ..............you didn't choose the option Selection Only in the Blender .dae exporter.

In Blender there is a big difference between adding mesh primatives in Object mode and adding them in Edit mode.

If you add 6 cubes in Object mode you will have 6 separate mesh Objects.

If you add your first cube in object mode then tab into Edit mode to add the other 5 you will have one mesh object consisting of 6 cube

The single mesh Object when exported and brought into SL will have a Server weight of 0.5 and a download weight of less than one. Physics cost will be less than 0.5 aswell so the LI will be somewhere between 0.5 and 1.

Your doing it right for the Physics cube in Step 1. In step 2, don't bother with setting it solid , just hit the Analyze button. And leave Step 3 alone  :)


just to note: You can join separate mesh Objects  ........... In Object mode Shift select the ones you want to join and use the shortcut key Ctrl + J .    Tab into Edit mode and you will see that they will now be one mesh Object.

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First, in the LOD tab, the only thing you can set to "High" is the selector underneath the preview. That just controls what you see in the preview. It has no effect on anything that gets uploaded.

Assuming Aquila is right, and that you have now joined the cubes into one mesh object, you still have some choices, and you might learn from looking at these...


If you load your single cube into the physics with "Load from File", then that will be used both for the default convex hull, which you use inworld when the physics shape type is set to "Convex Hull" (on features tab of edit dialog), and for the shape you generate when you click "Analyze", which you use when you set the physics shape type to "Prim".  The first two objects in the picture are made that way, with shape type set to "Convex Hull" on the left, followed by "Prim". The physics shape display below shows you the physics shapes in blue*. The numbers show the physics weights, which are very low for these. The problem with these is that there is physics where there is no visible object. So when I sit on it (rounded square) it looks like I am sitting in mid air.

In the next two, I have used the high LOD, with all six cubes, as the phsyics shape, then clicked "Analyze". Againg the left of the two is with physics shape type "Convex hull and the right with "Prim". The shaope of the convex hull is better, and still low weight, but I couldn't stand on the lower cubes. I would slide off the sloped part of the hull. When it's set to "Prim", there are flat tops to the physics shape of all the cubes. So I can stand on it realistically, but the cost is a higher physics weigh, 2.2, which gives me a LI of 2 after rounding.

The last model is using a new mesh for the physics shape, in which the layers with two or three cubes have each been replaced by a single cube stretched to the right size. Again, used "Analyze" to make the physics shape from this mesh. Now there are only three cubes in the "Prim" tyoe shaoe shown here.Although the gaps are filled in, I can stabd properly on the lower cubes. So the behaviour is acceptable as long as I don't want to go through the gaps. Reducing the complexity of the physics mesh has reduced the physics weight to 1.1, which gives a rounded LI of 1.

*You can see this by using Develop->Render Metadata->Physics Shapes from the Develop menu.



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Following on from Drongles post of the many choices ..............

 He could have gone on to mention custum Physics meshes and whether they should be Analyzed or not ...........

I just wanted to illustrate the "choices" I would have taken to get both low LI and accurate physics for your 6 cubes example :


The physics mesh is a copy of the visual mesh but to save a little on the Physics costs I deleted the underside face of each cube. In the Uploader this Physics mesh was not analyzed in Step 2 of the physics tab.

6 cubes phys not analyzed.png

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To see the physic shape helped a lot!

I tried to reproduce each of your examples, Drongle. To see the physic helped a lot and I could figure out a few things so that's great :). How you did the last one is unclear to me tho and I couldn't do that one.


How do you know the physic weight of each of them after upload?

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Its just three boxes on to of each other. I made them by delecting all except the left and right facing outer faces in each of the lower rows, then selecting the twp remainig squares on a level and doing Mesh->Edges->Bridge edge loops. There are plenty of simpler ways of getting the same thing. For example, delete all except one of the cubes on each layer and the select the left or right face and drag it (GX) to the right place.

In the edit dialog, click the More Info link. That will give the weights, rounded to 0.1. You can't see the Prim type physics weight until you have uploaded ot. The weight in the uploader is the default Convex Hull type weight.

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