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Door Entry

beli Lorefield

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I've read all the links I can find and followed this threads https://community.secondlife.com/t5/Mesh/Mesh-house-with-invisible-physical-walls/m-p/2961241/highlight/true#M32350 one of the threads advice to take the house and put it on a new layer and start deleting extra all the gemoatry  (SP) However it's still not letting me enter the door I can walk through any other part of and the other door just fine. I've changed to Prim etc uploaded the physics mesh etc.. nothing is working.








I can't figure out what I'm doing wrong.. LOL I've watched all the tutorals I could find and still can't figure it out


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The dae file accessed through your second link contains a single <mesh> with no less than 122 <polylist>s. These are the sections created for each material assigned to parts of a mesh object in Blender (you have more than 130 materials defined - presumably some are not used. The large number of materials is almost certainly the source of your problems...

In the good old days, a single mesh object was limited to a maximum of 8 materials. If you provided more, the geometry assigned to the ninth and thereafter was simply omitted from the uploaded data. More recently an ill-advised kludge was added which allowed the upload of dae files with objects with more than 8 materials per mesh. It didn't really drop the restriction. Instead, it splits the object into multiple objects, each of which had 8 or less materials. These objects are then uploaded as a linkset. You have no control over the splitting. So your mesh must get split into (at least) 16 separate objects.

You haven't given precise details about how you made the physics shapes. This makes it difficult to infer what would happen with the split objects. If you are providing (an) explicit physics mesh(es), then you need to be aware that you need one object for each of the (split) objects in the high LOD mesh. If you don't, then the physics becomes rather unpredictable. Otherwise, I haven't studied in detail how the uploader makes the physics after it has split the mesh into multiple objects, but I would guess this is where your p[roblem arises, whichever method yopu may have used. For example, if the split object are less than 0.5m in any dimension (a single wall) then the triangle-based physics  would always behave as convex hull, with no door openings, even if set to "Prim".

There's a lot of possibilities here, but here are some recommendations. First, don't use any object with more than 8 materials in any mesh. If you really can't make do with 8, then don't rely on the unpredictable splitting by the uploader. Instead, split the mesh into multiple objects yourself. Then you know exactly waht's happening and you can make the physics meshes to fit. Bear in mind that using large numbers of materials means using large numbers of textures (unless they are the same, in which case they can be the same material!), which all have to be downloaded by every viewer observing your building. This is a terrible drain on everyone's resources. Secondly, don't rely on any of the internal physics model generation in the uploader. You can always do better with a custom physics mesh file. There are many threads in this forum with the details of doing this for buildings while keeping the doorways unobstructed.


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From what Drongle said about the number of materials in your house, I am wondering if you made it originally from prims and then exported a copy with the viewer.   Those huge lists of materials show up then automatically when you import the file into Blender.


This is of course a VERY good reason not to do that - LOL.   If indeed it is that issue, you can make NEW materials for the faces (so exterior, interior, window moldings etc.) and AFTER reassigning the materials to what you actually need you can delete all the material-01-03 (or whatever but something that looks similar to that in the materials pane) by highlighting and using the minus sign over on the side of the materials list.


Note (just in case I guessed correctly and if not then of course completely disregard) that exporting prims to make a house is not the best idea. It was used often when mesh was new but not only is it very inefficient, it comes with some issues.  It is still a very good feature IMHO in order to get the general shape and size of something if fitting into an area is important. 


Good luck! I hope it works out for you. You will likely be much smarter by the time you get this working :D.  


Edit: Drongle has made many great threads on physics models and there are of course different ways, hopefully he knows  the URL to one of those threads. In the meantime, here is a photo from the other day of a physics model for a doorway. It is made up of three cubes (two became trapezoids but still cube shapes). It worked perfectly. Note that the edges of the physics model don't touch each other.



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Hi beli :)

If this is the same building as last time then you need to do the following:

1: The inner wall that is a separate mesh object you can join to the rest of the building.

2: Optimize the building to remove all the unnecessary vertices/triangles/quads.

3: UV unwrap.

4: Export building as .dae

5: Create a physics model for the building.

6: Export  the physics model as a .da file.

7: In the SL mesh Uploader, load up the visual mesh as usual then open the Physic tab of the uploader and in Step 1 Upload the physics .dae file. Don’t touch any of the other options in the Physics tab.

8: When rezzed in world, Edit the building and in the Features tab set the Physics Shape Type to Prim.

 To Optimize the building :

1: In Edit mode select everything and then Mesh menu > Clean Up > Limited Disolve.

2: With everything selected from the Tools panel Remove > Remove Doubles.

3: In face select mode remove all the faces at the top of all the walls. (these will never be seen).

4: Check all over you mesh and remove any faces that are inside the walls.

5: Edit mode: with everything selected Mesh > Faces > Triangulate Faces.

6: As much as possible Merge vertices that are not contributing to the shape of the mesh to vertices that are. See image below. Note: to do this you may find that you need to delete some of the triangles and rebuild the walls. (The more time you spend doing this the lower the final LI cost of the building will be.)

Now that the building has been optimized it is easier to create a physics mesh for it. The Physics mesh should be made from as few triangles/quads as possible. And you should avoid having small or thin polygons in this mesh. The uploader likes to see big polys in the Physics mesh and will reward you by with a low Physics cost. If it finds small or thin polys it will punish you by charging a higher Physics cost.

1: Make a copy of the optimized mesh and move it to a different layer.

2: Use this copy as a guide for creating the Physics mesh. For the the Physics mesh the walls don’t need window openings. Any faces that join outer to inner walls around door openings should be deleted. See image below, when you have something like that as your physics mesh then you are ready to export it as a .dae file and use in in the Physics tab of the mesh uploader.


Some notes :

As Drongle has already said, If your visual mesh is a single mesh object then your Physics mesh must also be a single mesh object. Each visual mesh object has to have its own Physics mesh.

The overall size (bounding box) of the Physics mesh must be the same as the visual mesh. If it isn't then the uploader will squish or stretch to fit the Visual mesh's bounding box. That would result in the collision surfaces not being exactly where you wanted them to be .

I will send you the .blend file of the optimized and Physics mesh inworld so that you can take a closer look at it.

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Thanks Aquila. I was just beginning to do a similar optimisation and physics mesh from the dae file. Now I don't have to. Phew.  I will say a few things about the file though. It has some disconnected edges in that appear in the collada as <lines>. I think these are probably ignored by the uploader, but should be removed. It has tons of completely hidden faces and a huge amount of other redundant geometry. If it's used as the physics shape unanalyzed, it produces an error "degenerate triangles" which means triangles with zero area. I'm not sure where these come from. I guess all these problems could be from conversion from prims. So all that needs correcting as well as the excessive materials.

ETA: In fact, I think it would be much easier to make a completely new model, using the imported mesh as a plan, than to do all the necessary decimation. I expect it's the UV mapping that would give the most trouble for someone not familiar with it.

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 Aquila, Yes it is the same house, I redid it in blender as you suggested to try and learn a bit more about it.  I will take a closer look at it when I get home tonight from work.  Thanks for all your help. 


Drongle nope not built in world at all it was completely done in blender. Well at first it was done in sketch up but then Aquila  convinced me to give blender another try.. so been working in there.

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I didn't look at the .blend file you posted in this thread ....... i had presumed it was exactly the same as the one from a couple of weeks ago.

Your on the right track with the Physics mesh beli.

When i first tried to Upload the building with the Physics mesh , the Physics mesh wasn't showing up in the preview window but the uploader was still calculating the Physics cost as approx 10. And when rezzed there was no Prim option in the Physics Shape Type drop down.

First i tried was: in Blender delete ALL those materials from the Visual mesh. result was the same , no Prim option.

Second; I deleted ALL those materials from the Physics mesh object. This time i could see the (yellow) Physics model in the Uploader preview window BUT the uploader gave an error because it found triangles with too little or no area:

Next I went back into Blender and using the "thick black lines" shown in the preview window as a guide i found and removed from the physics mesh those troublesome triangles/quads.

as a side note: you can clean up your physics mesh some by using the Mesh  Clean Up tool



After removing the tris/vertices that the preview window had indicated , the building uploaded ok  :)  and I was able to change the Physics Shape Type to Prim and walk around inside the buildiing ( after scaling it up to make it big enough to do so )


Some notes:

When you have finished with your mesh in Blender but before exporting, in Object mode select each mesh in turn then open the Object menu > Apply > Rotaion ans Scale.

Physics mesh:   Make the walls two sided , sometimes its possible to walk through walls that only have one side. In Blender, open the Properties panel (N) and scroll down to the Shading menu and then enable Backface culling. In mesh a polygon/face only has one side. The other side does not exist. With Back face culling enabled you can see the real face and see that the other side of the face is not there.

For Physics/Collision surfaces the fact that the "other side" doesn't exist matters. It means that sometimes, especially if you are moving quite quickly you can move through the wall from the side that "doesn't exist" . so where ever possible a wall's Physics should have two sides;  Quads/tris for collision surfaces on both the outside and inside of the walls.

Also, with Backface Culling enabled you will see that most of your wals have the face on the outside ( thats called having the Normals pointing outwards) but a few are pointing inwards .......

To reducde the physics cost a little you could remove those remaining few faces at the tops of a couple of the walls ( for example, those 2 wall sections that were giving errors in the preview window have those unnecessary faces )

you are almost there :)


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Was that the file you meant to post ?

I ask because it hasn't been optimized and there is no Physics mesh in that file ?


beli wrote :  "Okay I'm about to give up and just redo it (again) ............" .   I think that would be a good idea :)


The best advice you have recieved in this thread was from Drongle when he said "ETA: In fact, I think it would be much easier to make a completely new model, using the imported mesh as a plan, than to do all the necessary decimation. I expect it's the UV mapping that would give the most trouble for someone not familiar with it."

I would suggest you put asside the luxury Beach House project for a while and start with a simpler Beach Hut :)

In the images below I have tried to show the workflow for creating a basic hut. I deliberately left the roof of so that you  see inside. (note: there are many ways to create such a model, this is just one of them )

It may take a while even to get this done but you will learn alot of what you need to know and become more confident with using Blender before tackling more complicated models.

Also you will find that sorting out problems along the way will me simpler and less frustationg for you :)

















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