View Full Version : GI question
05 May 2002, 03:19 AM
If I create a big shere with a constans material in XSI and put for example a plane with a shere inside this spere, turn on GI for the light and the objects, then how come I dont see one of those soft round shadows GI usually causes? If I do the same in for example Lightwave it creates a nice shadow under the sphere. is this because LW has radiosity and not GI as XSI? Whats it the difference between GI and radiosity?
05 May 2002, 12:42 PM
Try Final Gathering instead of GI
Here's some explanations
Hope this helps
05 May 2002, 07:31 PM
Sure that helped a lot.
It sais Arnold is about three times the speed of MR, but I guess thats for MR 2 and not MR3, does anyone know how MR3 compared to Arnold and other renderer on GI and FG?
Lightwave has both GI (Global Illumination) and Radiosity. GI is basically the global luminosity of a scene, while Radiosity is the calculation of diffused reflections of lights in the scene.
05 May 2002, 10:22 AM
MR3's GI and FG is much faster than MR2.x's,
Have u ever see the benchmark result,sometime it's... really fast!
05 May 2002, 01:45 PM
I think that this is the page you are talking about.... http://users.pandora.be/geert.deleu/benchmark.html
05 May 2002, 05:33 PM
@@Lightwave has both GI (Global Illumination) and Radiosity. GI is basically the global luminosity of a scene, while Radiosity is the calculation of diffused reflections of lights in the scene.@@
Maybe i'm wrong but GI i think is the general term that includes all these indirect lighting effects whenever u call it radiosity or photon mapping.
GI is illumination that takes into account light transmitted from other objects, so i can't understand what u mean by saying that LW has both of them.. XSI supports GI, and photon mapping can compute the radiosity effects from diffused reflections such as "color bleeding".
Also XSI can compute specular reflections too (caustics) something that some traditional radiosity renderers (Lightscape) can't.(i don't know about LW).
Anyway i think that mr EdHarriss can explain better than me since he's the rendering guru here.:thumbsup:
05 May 2002, 09:41 PM
Global Illumination does not mean Radiosity. You can see it like this.
Global Illumination is created directly by the scene! Means all materials "create" or rather reflect the rays that will illuminate the whole scene (thats why it is called indirect lighting).
Radiosity "throws" the rays into the scene (diffusion). When looking at the Radiosity algorithm you will see the difference! I am not Softimage user but I know Lightwave and Cinema 4D for example and thatīs the way it works for them too. Shouldnīt be otherwise in any other applications (is almost impossible cuz it is a constant algorithm, like gravity etc.).
Photons have usually no relation to Radiosity or GI. It belongs to Caustics calculation (but almost anything is possible nowadays :). Donīt know SoftImage. So if it is, what is it good for? Canīt figure out what for? Thanks.
05 May 2002, 10:28 PM
@@Photon Mapping has no relation to Radiosity or GI. It belongs to Caustics calculation. @@
i think u r wrong.. here is a part from what the manuals in XSI write..
"In SOFTIMAGE|XSI, real-life lighting is simulated with global illumination. Global illumination includes both direct and indirect lighting caused by diffuse reflections. Photon (or light) rays emanate from the light source in all directions and bombard the scene. When these photons hit an object, some stick and others are reflected and refracted. These reflected and refracted rays go on to illuminate other surfaces. "
so as u see photon mapping is another solution to the classic radiosity algorithm and it's not only caustics..photons r emmited from a light like in radiosity renderers and calculate both diffuse and specular reflections.
i didn't say that GI is radiosity..i said it's illumination that takes into account light transmitted from other objects, for me it's a generic term for both solutions..
Anyway i don't know LW..in 3DVIZ for example it says "use radiosity" in XSI "GI" but the result is the same..(i hope u know what i mean)..
05 May 2002, 10:50 PM
@@Photon (or light) rays...@@
I am myself programmer, so I know it is almost impossible to write a new algorithm for Radiosity (why should anybody anyway?). As you can see, the description defines photons as light rayz. Just good written! ;) And as I said, I am not a SoftImage User, but this is too obvious. Radiosity and Photons... Canīt imagine what this can be good for (could please anybody tell me?) I guess they just use it to describe the same.
And SoftImage talks Global Illumination and not Radiosity!!
It is definitely not the same. Not at all. And GI CANīT be a global term for both of them. (nice try ;) But I know what you mean.
Thatīs the hard life we gotta live with every day. Everything in 3D Art must be defined and exact.
Sticking rayz...nice words! gotta remember these ones.
To 3DVIZ, I donīt know this app too but for XSI: I canīt imagine that an app like XSI only has the option to set GI and thatīs it! So either there are other options in other places (material manager of something like that?) or XSI includes the Radiosity within the GI. But that would be a shame.
The best and fastest Radiosity and GI Renderer I have seen until now and that seeks for enemies in this category (but wonīt probably find some in the near future) has got Cinema 4D. You canīt imagine how nice it works. Pretty cool.
I am still waiting for my Softimage demo cd. :)
P.S.: I like this forum.
05 May 2002, 11:50 PM
@@Radiosity and Photons... I guess they just use it to describe the same. @@
this is the classic "name game"..the result is the same
@@Radiosity and Photons... Canīt imagine what this can be good for (could please anybody tell me?)@@
is your question about radiosity, photons or both?!! for me "color bleeding" is the most important thing they offer..u can always set up a scene with a lot's of lights and simulate "radiosity":)
@@I canīt imagine that an app like XSI only has the option to set GI and thatīs it! So either there are other options in other places (material manager of something like that?) or XSI includes the Radiosity within the GI. But that would be a shame. @@
there r options within the lights the materials and the object itself (if u want it or not to take place in the sollution).
Can u really tell me something radiosity can do that photon mapping can't?:)
i don't know Cinema4D (this is our problem..we know different applications:) ) but can it calculate caustics?..
one difference i can tell u between e.g Lightscape and XSI is that the first has radiosity solution which is geometry dependent in calculations and the second not (it depends on the number of emmited photons), for me this a plus for the XSI.
anyway, when u'll have your XSI demo cd and have a look at it let me know your opinion..
05 May 2002, 12:15 AM
@@is your question about radiosity, photons or both?!! for me "color bleeding" is the most important thing they offer@@
my question was how photons and Radiosity can play together. What do you mean by color bleeding? Sorry, I am german.
@@Can u really tell me something radiosity can do that photon mapping can't?@@
Photon Mapping seems to be Radiosity!! And by telling me that in XSI it is only GI BUT you can also modify the different channels (in lights etc.) then I know Radiosity and GI are taken together in XSI! Da.. shame! Because the options in the channels are GI options! And your photon mapping seems to be Radiosity. And the Photons are only normal Rayz, thatīs for sure.
But you asked if Radiosity can do something your photon mapping canīt. Do you know the Arnold Renderer? Is this possible with photon mapping?
@@i don't know Cinema4D but can it calculate caustics?..@@
Yes, of course it can. Pretty good.
@@it depends on the number of emmited photons@@
That now clears any doubt I had! Emmited Photons. Radiosity emmits light rayz and you can normaly set the amount of rayz that will be emmited. Means the so-called Photons are the usual rayz, just named otherwise. Nice trick! :applause:
The same in Cinema 4D.
I will write my impressions down here when I get the cd.
All the Best
05 May 2002, 12:54 AM
well here i'm again!!
my english r not good too(i'm from greece). anyway in very simple english color bleeding is when one object influences another's color..e.g a red sphere near a white wall..
@@Do you know the Arnold Renderer? Is this possible with photon mapping? @@
i've seen images from this renderer and yes of course u can do that with mental ray(the renderer in XSI).
here is what mental images say about mental ray:
global illumination permits physically correct light simulation, which combines forward and backward ray tracing to simulate all possible light paths and light interaction from light sources to the camera, including indirect lighting, light focusing, translucency, glossy reflectors, and radiosity, without the need to manually prepare and combine each effect separately
caustics (light patterns caused by refraction or reflection of light, such as bright spots caused by lenses or bottles, and underwater light patterns)
algorithms for global illumination and caustic simulation is independent of geometric scene complexity
volume caustics: focused light made visible as a beam in fog or other diffuse media in volumes
multiple volume scattering: light interreflecting diffusely in fog or other media, such as the backscattering glare of headlights in fog, or light transport in clouds, or halos around bright light sources in fog
fast two-phase final gathering algorithm speeds up global illumination by an order of magnitude compared to mental ray 2.1
motion blurred caustics and global illumination cast by moving objects or moving lights"
so as u see it rocks..:). ok seriously , do u understand now what GI makes in XSI?
@@then I know Radiosity and GI are taken together in XSI! Da.. shame! @@
Can u explain me why it is a shame?anyway for more information u can visit..www.mentalimages.com.
i have to confess that i'm a little bit confused now with all this terminology (i'm not a programmer :) ) but since photon mapping in XSI offers me what radiosity renderers offer in other apps then it's ok for me!:)
All the best too
Aufwiedersehen..!!!(he he, i know some german words)
05 May 2002, 01:20 AM
ah ok then cinema renderer supports "color bleeding" too.
Arnold renderer effects are supported too.
ALL effects that come with the mental ray renderer are supported by the cinema 4d renderer too. Only the blurred Caustics are not supported I guess. Donīt know really. So Cinema 4D renderer Rocks too! :thumbsup:
@@do u understand now what GI makes in XSI? @@
That is almost the same what the cinema renderer does! It seems you wanted to defend yourself, but that was a quick u-turn for your defense, cuz your posting supports everything i was telling before! :applause: thanks for that.
@@Can u explain me why it is a shame@@ It is a shame because
the possibilities are more limited, when you do not have the chance to edit some options that are edited automatically and that could maybe optimize the ligthing to your 100% wish! Thatīs why it is a shame. Or do you want to disagree that less options are good? Donīt think so. It first appears cool because it is so easy to set up the GI but I prefer to set the options for myself. Got more control then. You understand what I mean?
I knew Mental Ray before and I think it is a real great renderer because the quality is really good, but there are always some things I would like to be improved. But I guess there will never be a perfect renderer. Do you all agree? :)
I have seen XSI in action on the Cebit this year and I liked the layout and especially some modeling tools that are missing in Cinema or Lightwave completely. So I am looking forward to the cd... :)
Woher kannst du denn deutsch? Auf Widersehen ist natürlich nicht gerade viel, aber manche können noch nicht mal ein Wort, also wird dir das hoch angerechnet! ;)
Now, to your dictionaries, steady, read! :thumbsup:
05 May 2002, 07:07 PM
hi..wie geht's? ;)
@@It is a shame because
the possibilities are more limited, when you do not have the chance to edit some options that are edited automatically and that could maybe optimize the ligthing to your 100% wish!@@
i'm not a programmer like u but mental ray is not so limited as u might think..i'm an end user but for someone who has the knowledge he can push it's strong capabilities even further..
i think when u'll have the demo cd u'll be able to judge this yourself..!!!
now about defending myself..i wasn't actually doing that..everything i wrote r things that mostly i read somewhere and believe me even Jeremy Birnn in his book "rendering and lighting", talks about this "name game" between the radiosity and photon mapping..(and u belong to the category he say's that some people reserve the word radiosity for specific algorithms and photon mapping as an alternative to radiosity).
Anyway i enjoyed this thread even though i think it went too personal between us, i hoped that someone at your "level" would post his opinion too but it's ok..!!!
By the way Lightscape which is a radiosity dedicated app doesn't have more " customizable options" than XSI, only the approach is different..
@@I knew Mental Ray before and I think it is a real great renderer because the quality is really good, but there are always some things I would like to be improved.@@
all people might want something more from the app they use and this is good for development..i believe mental images will keep on improving their product..and GI or whatever they name it is only a part in the whole product..don't forget that Renderman is the de facto in most future film productions with no radiosity solution..
ok, now that u "won" u have to treat me some beers..!!:beer:
Hope to see u in another tread !
(who knows maybe u'll need some help from this forum when u'll have your XSI!!!!)
05 May 2002, 12:30 AM
isn't it much simpler than all that? Aren't radiosity and photon mapping different methods of calculating global illumination?
05 May 2002, 09:22 AM
@@hi..wie geht's? @@
:) Gut und dir?
You are right, I enjoyed this thread too. I didnīt want to get this too personal.
Sorry, with the beer, but "Griechenland" is a bit too far. :)
But I will definitely need help in this forum when I get my cd.
All the Best
01 January 2006, 06:00 AM
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