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

[Dahlia Trimble]

There must be some support for skeleton or morph animation of meshes in the
viewer as the avatars use those techniques. I have no idea if they could be
applied to other meshes.

On Thu, Mar 19, 2009 at 5:54 PM, SignpostMarv Martin
<me at signpostmarv.name>wrote:

> Didn't I read something about the possibility for sculpties to be
> animated/manipulated with shader language code ?
>
> How would arbitrary meshes be animated/manipulated ?
>
>
> ~ Marv.
>
> Dahlia Trimble wrote:
>
>> One advantage sculpts have is they require little or no modifications to
>> the SL asset storage/distribution model. I'm not sure how other mesh storage
>> methods would fit into this model, but I suspect some modifications would be
>> required.
>>
>> One problem I have with sculpties is the lack of precision for the vertex
>> elements as a result of quantifying them to 8 bit integers to convert them
>> to a color. Another is the need for square or rectangular arrays of vertices
>> which makes some techniques of free form mesh modeling difficult or
>> impossible as arbitrary polygons cannot be added or deleted.
>>
>> Still, I am impressed with the cleverness of sculpted prims and although I
>> do share your desire for more flexible means of designing meshes for SL, I
>> am grateful that sculpties exist and are being improved upon.
>>
>> On Thu, Mar 19, 2009 at 4:53 PM, Dale Mahalko <dmahalko at gmail.com<mailto:
>> dmahalko at gmail.com>> wrote:
>>
>>    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
>>
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