[x3d-public] Shadows
Andreas Plesch
andreasplesch at gmail.com
Tue Oct 6 08:31:54 PDT 2020
Here is how sketchup does shadows
https://help.sketchup.com/en/sketchup/casting-real-world-shadows
Q1: yes, with the on Faces option, and the ability to use any light as
source for shadows. The Dark slider would correspond to the value
shadowIntensity
-Andreas
On Tue, Oct 6, 2020 at 9:11 AM GPU Group <gpugroup at gmail.com> wrote:
>
> 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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--
Andreas Plesch
Waltham, MA 02453
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