[sldev] 3D mesh support, vs lossless compressed sculpts

[Dale Mahalko]

It occurred to me recently that LL's reasoning for not supporting raw 3D
meshes as a prim type is basically invalid, what with how SL functions right
now.

The whole premise behind sculpted primitives was the idea that wavelet/JPEG
lossy compression could be used to store "organic" shapes that don't have a
very definite shape or form. The lossy wavelet compression of the RGB map
allows the data size to stay very small on the asset server, and that this
could not work if applied to storing and rendering mesh data.

However, that whole argument was thrown out the window after people kept
demanding precision in sculpted shapes, and some time ago someone at LL said
"Okay, FINE, we will allow the option of lossless compression for RGB
sculpt-map uploads" and support for this lossless uploading has been added
into the viewer.



So, uh, if lossless compression of sculpted primitives is permitted, doesn't
that mean that there could equally be support for lossless compressed 3D
mesh uploads, like traditional 3D editors use?

There apparently isn't really any reason to prevent mesh uploads anymore, at
least as long as the meshes are very small and simple, and the largest
uploaded mesh byte size is equal to or smaller than the most randomized,
incompressible compressed sculpt-map.



Allowing use of small meshes would be more efficient for the 3D renderer
anyway. Since sculpts have a fixed number of triangles, if your model does
not need the triangles for detail then they need to be "bunched up" into a
pile to get them out of the way, possibly tucked inside the model so they
don't show. But these unnecessary bunched up triangles are still being
processed by the 3D renderer whether or not they are needed.

LL's own sample sculpt maps demonstrate this problem, like with the S-shaped
sculpt that has a ton of prims scrunched up on it, and which could drop 50%
or more of the triangle faces on it and still look good.

 So sculpted prims actually add to 3D scene rendering lag and contribute to
a lower framerate and poor performance because they do not and cannot "turn
off" unneeded triangle faces, vs a mesh which just simply would not include
any more detail triangles than the mesh actually requires.



But there seems to be major LL heel-dragging against implementing actual 3D
mesh support and making models a heck of a lot easier to build in external
editors, vs the arcanary of sculpts that very few people understand or can
use effectively to reduce prim usage.

So, I am not expecting this post will change anything. But oh well, I
thought I would bring up this small detail for discussion. The sldev list
has been pretty quiet lately anyway.. ;-)

- Scalar Tardis / Dale Mahalko
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.secondlife.com/pipermail/sldev/attachments/20090319/000da8a1/attachment.htm