[x3d-public] X3D working group meeting Friday on TextureProjector nodes: special light or texture-mapping technique?

[GPU Group]

Either / both - like MultiTexture a parameter could say if you want to (add
and clamp) or multiply or replace.
-Doug

On Tue, Oct 13, 2020 at 11:36 AM Don Brutzman <brutzman at nps.edu> wrote:

> We said about 10 days ago that we could look this Friday at how the
> Projective Texture Mapping nodes interact with lighting equations.
>
> [Doug can you join us please?  Anyone else?]
>
> Wondering if X3DOM or X_ITE have implemented these nodes.
>
> Dick and I took another pass at this topic today and uncovered a
> fundamental ambiguity: is each node a light, or simply a texture-mapping
> technique?
>
> =============
> Use case. Shape/Box in a scene with no lights (and headlight="false").
>
> 1. Shape/Box with Appearance/Texture applied is not rendered.
>
> 2. If a light, TextureProjectorPerspective applied to Shape/Box makes it
> visible.
>
> 3. If solely a texture, TextureProjectorPerspective applied to Shape/Box
> does not make it visible.
> =============
>
> We had quite a discussion about whether it was (case 2) or (case 3).
>
> Undoubtedly this kind of thing was behind your questions before, "how to
> apply these nodes in the lighting equations?"
>
> Summary of specification-editing points follow, these are checked into
> Github as well.
>
>
> EDITORS NOTES.
>
> a. (case 2) Is this node a white light modified by the texture? Does it
> need an ambientIntensity field in the abstract node? If so, then
> X3DTextureProjectorNode must implement X3DLightNode, rather than
> X3DChildNode.
>
> b. (case 3) Is this node simply a texture that is applied to geometry
> instead? If so, then how is that texture merged with any other texture that
> may already be present?
>
> c. If added in X3DTextureProjectorNode, textureTransform affects the
> texture prior to being projected.  Seems like a good idea.
>
> d. If (case 2) these nodes are light sources, are the similarly part of
> shadow definition? If not (case 3), then might need to state that this
> effect is not occluded by intervening geometry.
>
> We think that most intuitive (and likely most effective) approach is to
> treat the nodes as lights and go with (case 2)... hope we can reconcile
> this.
>
> all the best, Don
> --
> Don Brutzman  Naval Postgraduate School, Code USW/Br
> brutzman at nps.edu
> Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
> X3D graphics, virtual worlds, navy robotics
> http://faculty.nps.edu/brutzman
>
> _______________________________________________
> x3d-public mailing list
> x3d-public at web3d.org
> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://web3d.org/pipermail/x3d-public_web3d.org/attachments/20201013/efafbb37/attachment-0001.html>