Hi guys,
here´s a link to two samplescenes that I hope illustrate
problems with the current FG implemenation found in
XSI 6.0. (130kB, XSI6.0, FG enabled, watch _underscores)
http://www.hafenlola.com/downloads/Ley_samplescenes.zip
I´ve been mailing back and forth on these with Halfdan
and would now like to make sure what I´m experiencing
is reproduceable by others, leading to similar guesses for
a more userfriendly solution. ½ also supports this realitycheck.
*Scene "wrong_scaling_FGintensity_with_objectsize.scn"
has two materials available in the explorer, the one assigned
the FGray emitting grid is animated to have it´s intensity(color)
scale divided by the increasing object size, this is to create an
illustrative workaround for the way FG light should behave imho:
"A light with the intensity of 1 emits the same amount of light
into a scene regardless of it´s actual size, only an increase in
the lights intensity leads to an increase in the amount of light
and extends the lit area"
If you assign the other material provided you get default
behaviour, the intensity scales with the size of the object
and pushes the boundary of the lit area outward. This
leads to the second scene showing that something´s wrong
with the internal calculation of FG based on absolute world units.
*Scene litregion_not_expanding_with_intensity.scn*
Please render frames 1 and 100 and compare the intensity
of the emitting grid with the resulting lit area, you´ll notice that
even thought the intensity is increase by factor 100, the lit area
isn´t growing accordingly but clamos at roughly 10 softimage units.
Even with the lack of a user exponent for the calculation (which
at least Maya has) one would have to expect soemthing like:
lit area (e.g. default falloff max) = intensity/(exponent)=intensity/2(fixed factor?)
It seems due to whatever reason, the above formula is broken by
having been hardcoded to max intensity = 1, resulting in a fallof
clamped at a maximum 10 softimage units, cropping away any
FG effect in a farther distance, exept when you scale the emitting grid.
This proves there is something wrong with the implementation of the
internal mR unitsizes and worldsize, scaling the object scales the effect
internally, instead scaling the intensity should scale the max fallof distance
since any default clamping at (roughly) 10 xsi units is counterproductive.
I´d go further indepth but I guess this e-mail is getting too long allready,
while I´d really welcome any feedback as I hope this issue can get changed
to the better asap.
Kind Regards,
tim
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