[whatwg] <model/>: A 3D Equivalent to <img/>

[Simon Fraser]

On Nov 2, 2009, at 4:26 PM, Brian Blakely wrote:

> * Though it does not have properties for clipping, Webkit's proposed
> implementation of 3D CSS does have them for perspective.  Clipping,
> lighting, texture stretching and additional considerations could also
> be a part of that spec, but those are discussions for the CSS WG.
>
> Without a 3D media element, none of that work can be done.

Implementing your proposal would require that the model and surrounding
CSS-transformed content be implemented via the same 3D engine, sharing
a common coordinate system. That vastly increases the burden placed on
an implementor of 3D transforms: suddenly wafers in space are non longer
sufficient, and you need a new engine with support for all the features
required by your <model /> content (which also needs to be specified  
somewhere).
You can't just glue a 3D-rendered model into an environment with  
CSS-3D-transformed
HTML elements and expect them to share a common 3D space.

> * This proposal of a model  can be considered a direct 3D analog to a
> PNG, and its height and width could certainly be modified in the X-Y
> axes on which 2D elements live, affecting document flow in that
> fashion.

A 3D analog for <img /> is a fine goal, but the primary issue is that  
there is
no 3D file format which is accepted as a standard for this kind of  
use. Even
if there were, the analogy breaks down because 3D is structured data;  
the author
wants to be able to address certain objects in the 3D scene in order to
animate them, or do click handling on them, or whatever. There is much  
more
complexity here than there is with images. In this sense, <model> is  
as much
a black box for 3D as WebGL on a <canvas> is.

A further issue with this proposal is that it doesn't address another  
request,
which is to integrate HTML content into a true 3D scene (e.g. a <div>  
mapped
onto a sphere, with operational hit testing etc).

> * Webkit's implementation of CSS does not remove 3D-ified elements
> from the document flow, the perspective of that flow is merely changed
> only for the affected elements.  3D and 2D elements can exist
> side-by-side that way as well.

Simon