[x3d-public] TextureCoordinate point range…should be reduced?

[John Carlson]

Since I’m the one specifying ImageTexture, it’s good to know that if
repeating is turned off, negative values will be clamped to 0, as I
struggle to read the standards.

So I’m not turning off repeating anytime soon.

John

On Wed, Nov 29, 2023 at 10:46 PM Brutzman, Donald (Don) (CIV) via
x3d-public <x3d-public at web3d.org> wrote:

> Thanks for additional insights.
>
> Please note current URL is the "IS proof" version, not CD Committee Draft
> (which is pretty old and no longer in use).  We've kept old versions online
> in case any sleuthing is needed, but they will go away at some point.
>
> *
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-IS.proof/Part01/components/texturing.html#TextureCoordinates
>
> 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
> https://faculty.nps.edu/brutzman
>
> -----Original Message-----
> From: x3d-public <x3d-public-bounces at web3d.org> On Behalf Of Michalis
> Kamburelis via x3d-public
> Sent: Tuesday, November 28, 2023 9:06 AM
> To: Extensible 3D (X3D) Graphics public discussion <x3d-public at web3d.org>
> Cc: Michalis Kamburelis <michalis.kambi at gmail.com>
> Subject: Re: [x3d-public] TextureCoordinate point range…should be reduced?
>
> Any texture coordinate value is valid, even negative, even -9999, and you
> can find 3D models indeed using them. That's true for any 3D software,
> format and API (Blender, X3D, glTF, OpenGL..).
>
> The interpretation of values outside of 0..1 range indeed depends on the
> "repeatS" / "repeatT" / "repeatR" (for 3D textures) values. The
> specification already explains this, see
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD/Part01/components/texturing.html#TextureCoordinates
> , "18.2.3 Texture coordinates".
>
> Note that TextureProperties node, if present, overrides the "repeat..."
> fields, with a bit more capable "boundaryMode...", see
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD/Part01/components/texturing.html#TextureProperties
> . See also CGE / view3dscene docs,
>
> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcastle-engine.io%2Fx3d_implementation_texturing.php&data=05%7C01%7Cbrutzman%40nps.edu%7C8248f9179ea24684111408dbf0348f64%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638367882107278434%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000%7C%7C%7C&sdata=DXTLzUWwYjF4Jr04Q4ZA3Go%2FW568712rK5cl6rw1oA8%3D&reserved=0
> , where we explain what we support (and why we do not plan to support
> "clamp to border", but we support all else).
>
> Regards,
> Michalis
>
> sob., 25 lis 2023 o 06:15 John Carlson via x3d-public <
> x3d-public at web3d.org> napisał(a):
> >
> > Can someone explain what a negative point value in a TextCoordinate
> means when the texture is an ImageTexture?  Does it have something to do
> with repeatS and repeatT?
> >
> > A section in the spec is ok.
> >
> > Thanks,
> >
> > John
> >
> > On Fri, Nov 24, 2023 at 10:32 PM John Carlson <yottzumm at gmail.com>
> wrote:
> >>
> >> 18.4.7 TextureCoordinate
> >>
> >> TextureCoordinate : X3DSingleTextureCoordinateNode {
> >>   SFString [in,out] mapping  ""
> >>   SFNode   [in,out] metadata NULL [X3DMetadataObject]
> >>   MFVec2f  [in,out] point    []   (-∞,∞)
> >> }
> >>
> >>
> >> I ran into a case where I was expecting texture coordinate point values
> from [0,1] in a texture mapping file, and I got values like -99999 an other
> negative values, which cause me to ignore the triangles and totally foul up
> the texture.  At this point, I don’t know what negative values mean in a
> texture coordinate point value and what I should accept for an IFS.  It
> seems like -99999 is dreadfully wrong, but per the spec above, any float
> value is acceptable.  I will check the IFS spec, but if no one has a use
> case, I recommend reducing the range of the texture coordinate point values.
> >
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