Physics model issues - High poly model creates larger physics bounding box. [Solved Sort Of :D]

[Aquila Kytori]

What Drongle is describing only happens if the the Uploader is creating the “secret” additional materials and the origin of the mesh is outside the bounding box.

 

Edit after reading Drongles explanation:   OOOOps, 

 

Edited again:  From Drongles explanation, the offset physics would be less noticeable if you moved the origin to the center of the bounding box. Move it up a little in the Z axis. 

[Drongle McMahon]

Or ... if it's only the bottom that matters, and you can put up with some obstruction above, move the origin to exactly 0.5m above the bottom of the mesh. (Still, the best thing is to redfuce the triangle count.)

[Drongle McMahon]

OK. I found in the source code how this happens. Basically, when the uploader decides to start the new material, it creates a new face with default values for the "Extents" *(the min and max vertex positions in each dimension). These are the unit cube around the origin, for some reason I can't fathom. So for the new material, it behaves as if it had detected vertices at the corners of that cube although it didn't. Now as it reads in more vertices, one of the limits will never be changed if all the real vertices lie to one side. Thus we are left with the bounding box that includes these ghost vertices. Should be very easy to correct this with two lines of code, copying the extents from the face before the split into the new face. I will do a jira. I hope nobody has been using this as a feature!

* For the technically minded, this happens at line 551 in lldaeloader.cpp, in function load_face_from_dom_polylist, where the default constructor for LLVolumeFace is used. That is in llvolume.cpp, lines 4562-4586. (current source). The load_face_from_dom_triangles function does the same. So it would presumably have the same effect if yoiu did get a material split, although that is less common and needs many more triangles.

ETA: BUG-41232

[Chic Aeon]

Ah, OK I get it now.  

 

I remember all these discussions from when the splitting the mesh with more than 8 materials change happened but I guess in my mind it was about too many materials and not poly count per material.

 

I did things two ways this morning.

I split the cloth into two materials (I had tested that BEFORE on the beta grid and it wouldn't upload but perhaps the uploader was having issues) and I tested as a linkset. 

 

Both showed up correctly in the preview pane of the uploader and rezzed on the ground with no extra physics above (that would have been worse in my point of view ) .   So good to remember AND I WILL should I delve into high poly in the future. 

 

Thanks to you both.

[arton Rotaru]

It should be easy enough to get such a cloth down to a few thousand, if not just hundreds of polygons without sacrificing it's appearance in-game. ~30000 polys is very high poly for such a game asset.

Just saying...:matte-motes-smitten:

[Chic Aeon]

I did cut it way down and that worked fine if small but in a larger size it wasn't at all eye pleasing -- way too lumpy. I did a hand remodel and not a desimate. I agree it is high. Not something I often do. 

[Drongle McMahon]

For what it's worth, I have put in another jira (BUG-41239)suggesting that the 21844 triangle per material limit for <polylist> geometry should be avoided, so that they would behave just like triangles, making this sort of complication much rarer. Don't hold your breath!

[Chic Aeon]

LOL. Well thanks for that.

 

It WAS INDEED a learning experience -- one I hope to NOT recreate in the future.  That's what happens when you get inspired by tutorials .   Everything that was problematic is uploade. The land impact is fine of course and the physics (with some redoing) is also fine. 

 

EXCEPT for the dropped cloth. I tried decimating (don't like that) and taking out a lot of edge loops and oddly those models came in higher than my previous upload with the giant "bouding box" physics.

 

I have noted time and time again that the same files (I make extensive notes on uploading) change land impact -- sometimes between beta grid and agni which kinda makes sense and sometimes within the same grid. I have no clue, but I guess I uploaded that file "on a good day" as the uploader liked it as 3 land impact where the new ones were MORE . There may be a scientific explaination there but I am tired. 

I promise not to delve into higher poly for a long while -- indeed I worked several days in old mode and it was quite enjoyable.

Thanks again for making me smarter.

 

[Drongle McMahon]

Were you using any auto-LODs? The GLOD thing that does the automatic LOD generation can produce different results each time it is run on the same mesh, and that can sometimes result in substantially different LI.