My technique is to start with the blender script that removes doubles, and cleans up illegal geometry. That is always my first and last step. Almost will load after that, except an object with no triangles. I have not found a way to find those except to hide each object. and anything left, that are just a dot I delete. There has to be at least one triangle for all 4 LODS, and since there are none it will abort and you will never figure it out. Luna's problem is very common when you use the viewer to make LODs. It can reduce a part below one triangle. One other loader issue if 8 materials max. Thats easy to fix in Blender, select the object and click Ctrl V (Vertex) and separate by Materials. The viewer will struggle with high counts of linked objects, so many meshes is better then one big bunch of mesh. It will rez much quicker too.
Please don't use the analyze button. it makes bad physics mesh where you cannot walk through doors. This has been known and cautioned by developers for many years. You get convex hull and you cannot make it physics type None or physics type Prim. Then you probably make it phantom and then use prims (ugh, they are always 96 triangles) to fix it.
I prefer to make a custom physics model. I start with a plane for a house floor, which is 2 triangles. That one sided mesh becomes my floors and walls (when I want walls). I extrude it to make ramps too, so stair steps are walkable. It is one object, and very low poly.
I rarely use the physics model settings in the viewer. I would say except for avatars, which only use two LODs, it is 99% cubes for me.
I rarely load anything except cubes as the physics model in the physics tab. It was intended to load a physics model directly. That is very difficult to do as the viewer requires a minimum of one triangle at the min/max X, Y, and Z of the model. That's why you always see cube models the same X,YZ size in preview. That really is painful, and really obsolete. If you can't get it just right, your physics gets enlarged or shrunken. And I don't want physical things hanging out there to trip over or fly into.
I load the model using the many cubes technique. One way is to load 100 cubes into blender and export that and then load it as a physics Object in the physics tab. But now the Latest Firestorm has this built-in. Assuming all your mesh objects have less then 21,000 triangles it should load in a few seconds.
Now up load the custom physics model on high physics and it will be in in a second. It's a simple set of planes.
Set that in place and walk on it. Select all of the main model, and make it physics type = None. Now link it to the physics model so the physics is last. It will remain type - prim. Now you have a very low poly physics model, that uses up the least amount of RAM and the least amount of precious CPU. And unlike prim shims on bad mesh, your house is one obect. You can take with you without leaving the invisible physics model behind.
One other trick to bring in very large models is use the cube at 0,0,0, in blender. Brink in chunks of your mesh along with the cube. That way you can zero in on the problem mesh and get it fixed. Use the arrows in the viewer x,y,and z coordinates to position each chunk you upload correctly by aligning cubes. It will be accurate to .01 meters
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