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X3D, IndexedFaceSet, "results are undefined" and profiles
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| Joerg Scheurich aka MUFTI 2005-11-09, 7:01 pm |
| Hi,
Can someone tell me the sense behind the following senses of ISO/IEC 19775:2005
(X3D):
The following criteria are required from each IndexedFaceSet
"otherwise the results are undefined" in ISO/IEC 19775:2005 13.3.6
- planar polygons
- 3 non-coincident vertices per polygon
- no self-intersection polygons
In ISO/IEC 19775:2005 table B3 (interchange profile) this criteria are
repeated as requirement for the interchange profile, but they are not
repeated in ISO/IEC 19775:2005 table E.3 (immersive profile) and
ISO/IEC 19775:2005 table F.3 (full profile).
Possible conclusion:
IndexedFaceSets in X3D files using the interchange profile may not
produce undefined results, while in the full or immersive profile
it may produce undefined results.
Do you see any sense in this ?
Standards are usually made to avoid undefined results. When you have
a multilevel standard, i can imagine the need to allow anything in the
full profile, but shouldn't it be avoided in a lower profile like the
immersive profile ?
so long
MUFTI
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| obviously if the three criterion are met the rendering engine can be
much simpler,
so what this says is that for the lower profiles this simpler approach
is all that is required, they are allowed to assume these criterion for
the data, and if the data does not comply then different rendering
engines are allowed to produce different results, hence undefined, it
is up to the data producer to obey these criterion. The higher
profiles are not and hence all compliant rendering engines have to
produce the same, defined, result.
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| Joerg Scheurich aka MUFTI 2005-11-09, 7:01 pm |
| > is all that is required, they are allowed to assume these criterion for
> the data, and if the data does not comply then different rendering
> engines are allowed to produce different results, hence undefined, it
> is up to the data producer to obey these criterion. The higher
> profiles are not
^
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Missing word here ? |
> and hence all compliant rendering engines have to
> produce the same, defined, result.
I have to admit, i do not understand this complicated sentence 8-(
Should i understand this in a way, that higher profiles are allowed to
produce different (undefined) results ?
so long
MUFTI
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The higher profiles are not ( allowed to assume these 3 criterion for
the data ) and so actually can't make any assumptions about the data
and so all have to produce the same result, hence 'defined'.
> Should i understand this in a way, that higher profiles are allowed to
> produce different (undefined) results ?
NO, this is what is allowed for the simpler profiles, if the data does
not comply to the 3 criterion.
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| sorry, re-reading my sentence i see it is a bit convoluted!
but here is the second sentence with the subjects included, if that
helps.
The higher profiles are not ( allowed to assume these 3 criterion for
the data ) and hence all compliant ( higher profile ) rendering engines
have to
produce the same, defined, result.
> Should i understand this in a way, that higher profiles are allowed to
> produce different (undefined) results ?
NO, this is what is allowed for the simpler profiles, if the data does
not comply to the 3 criterion.
| |
|
| sorry, re-reading my sentence i see it is a bit convoluted!
but here is the second sentence with the subjects included, if that
helps.
The higher profiles are not ( allowed to assume these 3 criterion for
the data ) and hence all compliant ( higher profile ) rendering engines
have to
produce the same, defined, result.
> Should i understand this in a way, that higher profiles are allowed to
> produce different (undefined) results ?
NO, this is what is allowed for the simpler profiles, if the data does
not comply to the 3 criterion.
heres the reasoning behind this.
~~~~~~~~~~~~~~~~~~~~~~
To support VRML on a small device, mobile phone etc., the standard does
not require a viewer, that only supports a lower profile, having to
deal with anything but the simplest surface arrangments. This then
means that its up to the 3d modeller to produce easily rendered data
for the lower profiles.
| |
|
| sorry, re-reading my sentence i see it is a bit convoluted!
but here is the second sentence with the subjects included, if that
helps.
The higher profiles are not ( allowed to assume these 3 criterion for
the data ) and hence all compliant ( higher profile ) rendering engines
have to
produce the same, defined, result.
> Should i understand this in a way, that higher profiles are allowed to
> produce different (undefined) results ?
NO, this is what is allowed for the simpler profiles, if the data does
not comply to the 3 criterion.
heres the reasoning behind this.
~~~~~~~~~~~~~~~~~~~~~~
To support VRML on a small device, mobile phone etc., the standard does
not require a viewer, that only supports a lower profile, having to
deal with anything but the simplest surface arrangments. This then
means that it is up to the 3d modeller to produce easily rendered data
for the lower profiles, and if they don't then the standard says you
can
not be sure what results you will get, ( undefined ) even on compliant
viewers.
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