[x3d-public] Shadows
GPU Group
gpugroup at gmail.com
Tue Oct 6 06:11:19 PDT 2020
Q1. would shadows look like SketchUp shadows?
Q2. does x3d have an appearance for the edge lines like SketchUp?
Q3. when does the SketchUp push/pull patent expire?
Doug Sanden
On Mon, Oct 5, 2020 at 5:08 PM Michalis Kamburelis <michalis.kambi at gmail.com>
wrote:
> As for the shadows color, I second what Andreas said: shadows are
> *not* black, shadows merely mean that light from a given light source
> doesn't reach there. The result of the shadows computation can be
> elegantly inserted in the middle of the existing light equations,
> light contribution is scaled by "(1-light.shadowIntensity *
> howMuchIsThisInShadow(geometryPoint,light))"
>
> As for shadows scope: for beginning, I would indeed leave it as-is,
> which means that
>
> - shadow caster == everything
> - shadow receiver == stuff that is affected by the light source
> (following the existing light source behaviour)
>
> In CGE I have a more flexible mechanism, to explicitly list shadow
> receivers, and control the shadow casters, but I feel that if we go
> this direction -> we go into complicating :) For reference, CGE stuff
> for shadow maps is on
> https://castle-engine.io/x3d_extensions_shadow_maps.php , in
> particular we have
>
> Appearance {
> ...
> MFNode [] receiveShadows [] # [X3DLightNode] list
> SFBool [in,out] shadowCaster TRUE
> }
>
> This allows to configure at Appearance of each shape whether it casts
> shadows, and from what light sources it receives shadows. It's very
> flexible, and frankly has very low usage in practice... Authors don't
> want to think about these details, they want to treat shadows as
> "simple property of the light source, and everything else should Just
> Work" :)
>
> For reference, I also looked at Unity shadows configuration:
>
> - https://docs.unity3d.com/ScriptReference/Light.html (search Ctrl+F
> for "shadows")
>
> - in particular the main property is "Light.shadows" ,
> https://docs.unity3d.com/ScriptReference/LightShadows.html with is an
> enum and can be None, Hard, Soft
>
> - there is also "Light.shadowStrength" ,
> https://docs.unity3d.com/ScriptReference/Light-shadowStrength.html so
> it matches Don's proposed name
>
> - each mesh also has settings to control whether it receives and/or
> casts shadows, https://docs.unity3d.com/Manual/class-MeshRenderer.html
>
> Regards,
> Michalis
>
>
> wt., 6 paź 2020 o 00:21 Andreas Plesch <andreasplesch at gmail.com>
> napisał(a):
> >
> > Michalis, Don,
> >
> > As a data point, I just checked and x_ite. Both allow and implement
> > [in] for shadowIntensity. x_ite probably generates the out event,
> > x3dom probably does not but that is not performance related.
> >
> > I feel that shadowIntensity works well as a name, and is self
> > explanatory. There is little risk of confusion with intensity.
> >
> > I do not think shadows would be expected to have a color. Shadows are
> > a deficit of light. The light itself is colored but shadows are not.
> >
> > Any thoughts on the scope of shapes which receive shadows ? All shapes
> > in the scene, eg. global, or just the ones in the scope of the light.
> > Scoped shadow would potentially perform better. Is there a situation
> > where there is scoped light, say a room in a building but the shadows
> > from the light should be shown outside the scope, eg. outside the room
> > ?
> > If there is a window in the room, shadows from window decorations
> > should be shown on the street outside. But this also requires that
> > light from the room gets out of the window, so would not be scoped to
> > the room anymore.
> > I think this example generalizes. So I think only shapes within the
> > scope of the light can receive shadows from obstructing the light.
> > Probably there is no need for spec. language on this scoping.
> >
> > -Andreas
> >
> > On Mon, Oct 5, 2020 at 5:54 PM Don Brutzman <brutzman at nps.edu> wrote:
> > >
> > > Understand what you're saying Michalis, hmmm. Authoring/performance
> tradeoff analysis:
> > >
> > > - If initializeOnly then no animation of shadowIntensity is possible.
> Seems like this is an important authoring option at run time to see if
> shadows are at proper intensity. Also a likely animation technique.
> > >
> > > - Meanwhile authors can control whether this parameter is exposed to
> end users by interface (typically it is not) and so avoid any performance
> clobbers.
> > >
> > > - When putting parameters in X3D specification we try to design for
> long term, browser cleverness and Moore's Law both integrate nicely over
> time.
> > >
> > > Naming curiosity: shadowIntensity indicates degree of darkness
> applied, as opposed to more-common intensity field which is degree of
> lightness/brightness.
> > >
> > > - Just wondering, perhaps we should call it shadowStrength or somesuch?
> > >
> > > Also wondering, shouldn't we specify "All shadows are black" in the
> prose definition.
> > >
> > > Have fun thinking about X3D! 8)
> > >
> > > ---
> > >
> > > p.s. Double reverse, in case anyone isn't dizzy yet:
> > >
> > > * Peter Gabriel, 'White Shadow'
> > > https://en.wikipedia.org/wiki/Peter_Gabriel_(1978_album)
> > > https://petergabriel.com/video/white-shadow
> > >
> > >
> > >
> > > On 10/5/2020 2:15 PM, Michalis Kamburelis wrote:
> > > >
> > > > Yes, (almost) exactly.
> > > >
> > > > The only change I would do to what Don wrote is that I would start
> by making shadowIntensity initializeOnly, i.e. [] instead of [in,out].
> While changing it at runtime is possible (as with everything), it could
> have very big cost when changing from 0 to 1. I'm not strongly opposed to
> [in,out], just saying I would start with [] and see at adoption in browsers
> and think about "upgrading" to [in,out] in next version.
> > > >
> > > > Regards,
> > > > Michalis
> > >
> > >
> > > On 10/5/2020 2:09 PM, Andreas Plesch wrote:
> > > >
> > > >
> > > > Hi Don,
> > > >
> > > > I believe the specifics is what we are trying to determine. I would
> > > > say, yes, exactly, such a signature and the abstract node
> > > > (X3DLightNode) would be how the field is applied.
> > > >
> > > > It would be backward compatible, with a default of 0, eg. no shadows.
> > > >
> > > > Let me also bring up that as far as I have seen lighting and shadow
> > > > casting in other frameworks often works on a per Shape (equivalent)
> > > > basis. Each shape defines for itself how it is lighted, and if it
> > > > casts or receives shadows. For shadows this approach can make sense
> > > > since shadowing is expensive and benefits from this kind of fine
> > > > control. I do not really think there are implications for a simple
> > > > shadowIntensity field in X3D but I thought it would be useful to
> > > > mention.
> > > >
> > > > -Andreas
> > >
> > > > W dniu pon., 5.10.2020 o 21:50 Don Brutzman <brutzman at nps.edu
> <mailto:brutzman at nps.edu>> napisał(a):
> > > >
> > > > Specifics please: are you gentlemen talking about adding
> backwards-compatible field signature of
> > > >
> > > >
> > > >
> > > > SFFloat [in,out] shadowIntensity 0 [0,1]
> > > >
> > > >
> > > >
> > > > to X3DLightNode (and thus DirectionalLight, PointLight,
> SpotLight)?
> > > >
> > > >
> > > >
> > > >
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD2/Part01/components/lighting.html#X3DLightNode
> > > >
> > > >
> > > >
> > > > =============================================
> > > >
> > > > 17.3.1 X3DLightNode
> > > >
> > > >
> > > >
> > > > X3DLightNode : X3DChildNode {
> > > >
> > > > SFFloat [in,out] ambientIntensity 0 [0,1]
> > > >
> > > > SFColor [in,out] color 1 1 1 [0,1]
> > > >
> > > > SFBool [in,out] global FALSE
> > > >
> > > > SFFloat [in,out] intensity 1 [0,∞]
> > > >
> > > > SFNode [in,out] metadata NULL [X3DMetadataObject]
> > > >
> > > > SFBool [in,out] on TRUE
> > > >
> > > > }
> > > >
> > > > =============================================
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > On 10/5/2020 7:08 AM, Andreas Plesch wrote:
> > > >
> > > > >
> > > >
> > > > > I think the exact interpretation of intermediate values would
> be
> > > >
> > > > > implementation dependent in any case. It may be ok to just
> stay that.
> > > >
> > > > >
> > > >
> > > > > "
> > > >
> > > > > shadowIntensity ranges from 0 to 1.0 [could be omitted
> because the
> > > >
> > > > > range is defined in the signature]. A value of 0, the
> default, has no
> > > >
> > > > > effect. A value of 1.0 has the effect that no light emitted
> by the
> > > >
> > > > > node reaches the areas where shadows are cast by shapes in
> the scope
> > > >
> > > > > of the light. A value between 0 and 1.0 has the effect that an
> > > >
> > > > > intermediate amount of light reaches shadowed areas. Support
> for
> > > >
> > > > > intermediate values is browser dependent.
> > > >
> > > > > "
> > > >
> > > > >
> > > >
> > > > > Only shapes in the scope of a light can cast shadows since
> only those
> > > >
> > > > > shapes are lit by the light. One general question then is
> which shapes
> > > >
> > > > > should be able to receive shadowing. Potentially all shapes
> in the
> > > >
> > > > > scene but perhaps it makes sense to restrict receiving shapes
> also to
> > > >
> > > > > the scope of the light ? The wording above does not offer
> further
> > > >
> > > > > detail which would mean that the browser is given room to
> answer that
> > > >
> > > > > question.
> > > >
> > > > >
> > > >
> > > > > -Andreas
> > > >
> > > > >
> > > >
> > > > >
> > > >
> > > > > On Mon, Oct 5, 2020 at 6:56 AM Michalis Kamburelis
> > > >
> > > > > <michalis.kambi at gmail.com <mailto:michalis.kambi at gmail.com>>
> wrote:
> > > >
> > > > >>
> > > >
> > > > >> From Castle Game Engine / view3dscene side, I can go for
> "SFfloat
> > > >
> > > > >> shadowIntensity" with this interpretation too :)
> > > >
> > > > >>
> > > >
> > > > >> Compared to my earlier proposal "SFBool shadows", the
> > > >
> > > > >> "shadowIntensity" is obviously more flexible, I can see the
> > > >
> > > > >> advantages. And with shadow maps, it is easy to support any
> > > >
> > > > >> intermediate value, e.g. allow 0.5 of the light to reach the
> surface.
> > > >
> > > > >>
> > > >
> > > > >> With shadow volumes it's not possible (at least not easily)
> but then
> > > >
> > > > >> the implementation can always go with simple Andreas'
> wording """0
> > > >
> > > > >> means no shadows, 1 means full shadow.""". We would need to
> say what
> > > >
> > > > >> happens for intermediate values in this case, e.g. "if
> implementation
> > > >
> > > > >> only supports 0.0 and 1.0, then any value >= 0.5 behaves
> like 1.0,
> > > >
> > > > >> otherwise (value < 0.5) behaves like 0.0".
> > > >
> > > > >>
> > > >
> > > > >> Regards,
> > > >
> > > > >> Michalis
> > > >
> > > > >>
> > > >
> > > > >> pon., 5 paź 2020 o 04:49 Andreas Plesch <
> andreasplesch at gmail.com <mailto:andreasplesch at gmail.com>> napisał(a):
> > > >
> > > > >>>
> > > >
> > > > >>> As motivation to make Shadows a high priority for the next
> version let
> > > >
> > > > >>> me share Holger's cool idea to use Sponza for shadows:
> > > >
> > > > >>>
> > > >
> > > > >>>
> https://create3000.github.io/media/examples/Navigation/NavigationInfo/example.html
> > > >
> > > > >>>
> > > >
> > > > >>> I could adopt it pretty much as is for x3dom:
> > > >
> > > > >>>
> > > >
> > > > >>>
> https://raw.githack.com/andreasplesch/x3dom/scopedLights/test/functional/scopedLights/inline.html
> > > >
> > > > >>>
> > > >
> > > > >>> (without the nice ParticleSystem, and with slightly changed
> > > >
> > > > >>> intensities and locations).
> > > >
> > > > >>>
> > > >
> > > > >>> The main required field for both x3dom and x_ite to enable
> shadows is
> > > >
> > > > >>> shadowIntensity. 0 means no shadows, 1 means full shadow.
> > > >
> > > > >>>
> > > >
> > > > >>> -Andreas
> > >
> > >
> > > 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
> >
> >
> >
> > --
> > Andreas Plesch
> > Waltham, MA 02453
>
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