[x3d-public] X3DParticleEmitterNode mass and surfaceArea accessType initializeOnly rather than inputOutput?

[Don Brutzman]

Wondering why X3DParticleEmitterNode mass and surfaceArea have accessType initializeOnly rather than inputOutput?

Way back when first defined, there was likely concern about computational complexity if changed at run time.

However these values would still seem to be variables in direct use at run time.  So being able to modify them would seem to have no computational overhead and might provide interesting animation effects.

Applies to ConeEmitter, ExplosionEmitter, PointEmitter, PolylineEmitter, SurfaceEmitter, VolumeEmitter nodes.

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https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/particle_systems.html#X3DParticleEmitterNode

40.3.1 X3DParticleEmitterNode

X3DParticleEmitterNode : X3DNode {
   SFNode  [in,out] metadata    NULL [X3DMetadataObject]
   SFFloat [in,out] speed       0    [0,∞)
   SFFloat [in,out] variation   0.25 [0,∞)
   SFFloat []       mass        0    [0,∞)
   SFFloat []       surfaceArea 0    [0,∞)
}

The mass field specifies the basic mass of each particle in mass base units. Mass is needed if gravity or other force-related calculations are to be performed per-particle.

The surfaceArea field specifies the surface area of the particle in area base units. Surface area is used for calculations such as wind effects per particle. The surfaceArea field value represents an average frontal area that would be presented to the wind, assuming a spherical model for each particle (i.e., the surface area is the same regardless of direction).
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Entered as Mantis 1307, https://www.web3d.org/member-only/mantis/view.php?id=1307

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