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paulselhi
11-27-2005, 01:03 PM
In C4D's AR if i render and save a solution for a final image at say 460 x 320 can i use that saved solution to say render at 800 x 600 ? OK i know i can but will there be any loss of GI accuracy ?

And while i am here does C4D's GI depend on scene size ? I see many mentions in other renders that their GI calcs are dependant of having real world scene scales, is this also the case for AR ?

Srek
11-27-2005, 01:33 PM
If you reuse samples from a low res rendering for a high res rendering the precision will go down and it becomes more likely that you can see artifacts or simply less precise lighting.
As for the second part, yes GI is scene size dependent, however the units used are irrelevant, only relative size is important. For example having a hughe sphere around the scene will lead to a rather inaccurate sampling of the main parts of the scene, since the distribution of the samples will be made depending on the whole size.

Cheers
Björn

paulselhi
11-27-2005, 01:39 PM
Thanks for clearing that up. Another question..when doing outside renders should you encompass the whole scene in a non visible sphere to bounce stray rays back into the scene ?

Srek
11-27-2005, 02:42 PM
I wouldn't do this, it would require exactly that kind of hughe sphere that would mess up your samples.
Cheers
Björn

paulselhi
11-27-2005, 03:13 PM
How does that affect hdri rad renders that use spheres ? If the sphere{s} are just slightly bigger than the scene will that be OK or is this an inevitable problem with HDRI and rad ?

Srek
11-27-2005, 03:23 PM
All GI renderings using a sourounding objects are influenced by this, the smaller the object the lower the number of samples can be.
Cheers
Björn

FantaBurky
11-27-2005, 03:41 PM
Wow, you two are having quite a nice chat here by yourselves... anyway that was all I wanted to add. cya

AdamT
11-27-2005, 04:18 PM
How does that affect hdri rad renders that use spheres ? If the sphere{s} are just slightly bigger than the scene will that be OK or is this an inevitable problem with HDRI and rad ?
Probably makes sense to put a compositing tag on the sphere with "receive GI" unchecked--but I haven't tried it to see what difference it makes.

STRAT
11-27-2005, 06:41 PM
In C4D's AR if i render and save a solution for a final image at say 460 x 320 can i use that saved solution to say render at 800 x 600 ? OK i know i can but will there be any loss of GI accuracy ?

as stated, you really must render a fresh solution at the same particular size you got in mind.

if you render a 640x480 solution and use it with a higher or lower res render, other than artifacts showing (as mentioned) the render tends to slow right down too.

and to simply answer your second part, Srek is spot on. it's all reletive. scaling your whole model up or down by 1000% for example wont effect render times.

Simon Wicker
11-27-2005, 07:22 PM
How does that affect hdri rad renders that use spheres?

the answer here is to apply your HDRI image to a sky object - the sky object has no polygons and no scale and therefore doesn't affect the distribution of sampling points in a scene.

i've read a few threads were people have decided this doesn't give as good a result as a polygon sphere but i haven't come across this myself.

cheers, simon w.

STRAT
11-27-2005, 07:31 PM
a polygonal sphere also needs allot more samples and takes allot longer to render than a sky object. how it compairesto overall visual accuracy and quality compaired to a sky object isn't a mass to write home about either imo. i'll usually use a skyobject for my hdr and ibl rendering, but sometimes i'll use a polygonal hemi-sphere, depending on the job in hand.

paulselhi
11-28-2005, 12:52 AM
thanks for your ideas everyone


I am rendering out a test archviz scene which i would be pleased if you could all have a monkey around with. I will start a new thread tommorrow on it, but basically i would be interested to see how everyone would go about lighting it...sorry i will post the file and a render later

edit..well it's only 1.00 am now so give me 1/2 hour and i will get some thing together

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