[x3d-public] Nurbs patch coloring

[Michail Vidiassov]

Dear All,

On Fri, Jan 26, 2018 at 4:36 AM Andreas Plesch <andreasplesch at gmail.com> wrote:
>
> If 2x2 textures would work, it.may be possible to use PixelTextures which could be constructed from the control point color information perhaps pretty directly. Actually, such a PixelTexture may be more appropriate  than a hypothetical controlColor MFColor field since the non control vertices would have to be colorized by some interpolation in a texture mapping like process anyways. But there may be an upper limit to the number of textures.
> Combining the textures into a single image gives the browser and player a chance to cache the image which would be beneficial for loading it for each surface. In theory, a single texture could be shared on the openGL level by all surfaces. But it would depend on the x3d player's ability to optimize.
> I thought I would mention that currently neither x3dom nor x-cite implement the NURBS component. So webgl limitations may be not be an immediate concern unless the goal is actually to target the web.

Since X3D v4 is being codified, maybe the idea of coloring NURBS
patches with "hypothetical controlColor MFColor field" instead of 2x2
texture is worth revisiting, even if only to be rejected.
The reasoning is the same: if a scene is built upon a mesh of NURBS
(say bezier) patches, the author may have the same reasons to wish to
assign colors to "vertices" of that mesh and have them interpolated
within "faces" as in the common case of a triangle mesh.
And having to always use textures instead of vertex colors has the
same drawbacks.
For example even the venerable OBJ format (that has that limitation)
is being "de facto" extended to allow for vertex colors, their great
usefulness (vis baking textures out of them) outweighing breaking
compatibility with the long established standard.

Sincerely, Michail



On the positive side since 2018 NURBS got implemented in WebGL X3D libraries