Ambiant occlusion in vray

[a23]

Hi,

I don't mean to be offensive, but a question like this can easily be answered using Google, and just clutters up the forum, ending up not being answered. Give Google a try it by entering: 'vray occlusion tutorial' :-)

I hope the answer to you question lies here: http://vray.info/news/n0103.asp, which will lead you to here: http://plugins.angstraum.at/vrayao/index.htm

Have fun,

AndY

[TiskO]

Ive already tried google, but again, i dont want a script. My work collegue is the same.

[alexyork]

as far as i can tell that script is just a fudge - not "real" AO. there is no "real" AO shader for Vray yet but I'm guessing it's probably high on chaosgroup's list of things to include in the next version. it's really no big deal anyway - just start a new instance of MAX, do an x-ref of your main scene file and set that to MR and render from there. each time you update the main scene file just update the x-ref and re-render.

[mr Bob]

As Ive said in a previous post Tisko , you could use a plugin called DirtyReyes it works on the same principles as an AO pass , its not perfect but it will do, I did hear many years ago it was free.

B

[Wiro]

Dirtyreyes is very old, slow and only available for max6 and older. It was great for simulating AO back when but you're way better off doing a skylight pass directly in VRay. Just plonk a white or grey material on your objects, set your enviro to white and turn on only primary bounce. Save it to an irradiancemap using a setting of -2/0 if you want to see fine detail.

Wiro

[TiskO]

Thankyou very much Wiro. Settings are perfect and the render look great.

[mr Bob]

Wiro cheers for clearing that up ....my lack of max knowledge shows badley ......see you in the canteen for a coffee later .......

B

[dprgb]

If you want ambient occlusion, just create a vraylight and set it to "dome." Then, create a light gray material and put it in the material override slot. Turn all the other lights off and render.

You can up the samples in the dome light to get a cleaner image, and also it does not need any GI preprocessing.

[cpnichols]

Don't mean to offend anyone, but AO is a just a means of faking GI for tools that can't create true GI in a resonable time. If you have access to Vray, you can create a full GI pass with only about 30% hit in rendering time that will give you 3 extra bounces of light and get all the color bleeding on top of that. You can then use your comp prog of choice to mult to result and get all a much richer image.

[Wiro]

Heya TiskO, I just realised you work at Monkeylab. Say hello to the other Matt, Petch and Octavio from me!
Actually Matt and Greg would know anything you need to know about VRay ;)

mr Bob, are you at Animal too? Haven't found any Berti Bassets in the kitchen :)


Wiro

[ThirdEye]

Since you work in Max and it includes Mental Ray just use it for the Ambient Occlusion pass and use Vray for everything else if needed. :shrug:

[cpnichols]

Since you work in Max and it includes Mental Ray just use it for the Ambient Occlusion pass and use Vray for everything else if needed. :shrug:

Doing an Ambient Occlusion pass in Vray would be a lot faster then MR. Plus, as I said, doing an Ambient Occlusion pass in Vray would be like having a Ferrari and never taking it out of first gear.

[Studev]

-----Doing an Ambient Occlusion pass in Vray would be a lot faster then MR. Plus, as I said, doing an Ambient Occlusion pass in Vray would be like having a Ferrari and never taking it out of first gear.----

That is just so true...

[CiaránMurphy]

Agreed about VRAY... why on earth ould you want AO when you an have the real thing! I suspect however that like the idea of a AO 'pass' it can be saved as a separate image and you can use layers in Photoshop to vary intensities etc. Of course this completely overlooks the fact that the VRay virtual frame buffer can show you all the passes/layers that go up to make the final image.

[cpnichols]

Agreed about VRAY... why on earth ould you want AO when you an have the real thing! I suspect however that like the idea of a AO 'pass' it can be saved as a separate image and you can use layers in Photoshop to vary intensities etc. Of course this completely overlooks the fact that the VRay virtual frame buffer can show you all the passes/layers that go up to make the final image.

Yeap... if you take the "raw GI" pass which includes color bleeds etc... and multiply it the same way you would an AO, you get a lot more out of it.

[ThirdEye]

the computation of AO is fast, flexible and can be baked. Also there's usually no flickering.

[ThirdEye]

Doing an Ambient Occlusion pass in Vray would be a lot faster then MR.

since vray doesn't have an AO shader how do you know it'd be a lot faster? Also it's not like he's got many options here, is it? Mental Ray is quite fast at AO if you ask me :shrug:

[cpnichols]

Having done a lot of AO with other rendering engines, I know that Vray is much faster and MUCH cleaner. Also you will get no flickering with the GI as it can be baked the same way that AO can: either through textures or through and Irradiance map.

There actually is an AO type shader in Vray, as well as about 4 different ways of doing AO, Skylight, Dome light, and now with the new "dirt shader..." All of which are very fast. So fast that you might as well bounce the light around a few extra times.

[mr Bob]

Im confused ....How can 1 full GI frame be calculated faster than 1 full frame of an AO pass, Surely there are a lot more calculations needed for a GI pass than an AO pass,please explain.I must admit Ive not seen any animation/vfx done in Vray at 2k but Id really like to see this wonder render engine in action. Do any firms use it for film /commercials

B

[cpnichols]

Im confused ....How can 1 full GI frame be calculated faster than 1 full frame of an AO pass, Surely there are a lot more calculations needed for a GI pass than an AO pass,please explain.I must admit Ive not seen any animation/vfx done in Vray at 2k but Id really like to see this wonder render engine in action. Do any firms use it for film /commercials

B


Let me clarify... One GI frame in Vray is faster then one AO frame in something else.

Also, there are many examples out there that use Vray.... The Nine Inch Nails video is a good one:

http://www.nin.com/visuals/index.html

look at the "Only" video done by David Fincher. All CG... All Vray

[francescaluce]

One GI frame in Vray is faster then one AO frame in something else.
this is not true in general.
AO is obtained by simply probing a ray until it reaches something
in a qmc distribution fashion. and one has near and far params to 'clip' it.
GI involves much more things to be considered and, at least there's
not a special 'mode' that you can enable, it generally involves also
the evaluation of the material obj hit by the GI ray. not last the
rays will travel at least until they've not hit the environment and also
there they will have to evaluate the env shader.
so, even if you set the GIray to get only one bounce and the
pass material to be a simple constant white color, GI should be slower
than an AO pass on the paper. that said if you say that vray GI is faster
than any AO pass the only thing you have to do is to prove it with some
examples... pratically.

ciao
francesca

[cpnichols]

Ok Francesca...

I have prepared some images to clarify what I am trying to say. Basically this whole thing started when I said early on this thread, using Vray just for AO is a waste since it can do GI in less time then most programs do AO. So here are some examples I have prepared...

Here is an AO pass on a scene that has approx. 1 million+ polies. These images were originally rendered at 800x600 and resized for the web to 400x300

Rendertime is 8 min 19 secs

http://www.redeyetales.com/forum/AO_MR_8m19s.jpg

I then set up an AO pass in Vray to be as close to the MR AO pass. I got this using the QMC sampling method...

Rendertime was 6 min 53 secs

http://www.redeyetales.com/forum/AO_VR_QMC_6m53s.jpg

But Vray has a much more efficient and high quality method of sampling using its irradiance mapping. So I set it up with that.

rendertime was 2 min 53 secs (a LOT faster):

http://www.redeyetales.com/forum/AO_VR_IM_2m50s.jpg

So why not bounce the light around a few more times. That is easy to set up in Vray. The following image also shows that the AO pass in this case is has a serious disadvantage over the GI pass, what bounces the light around.

Render time was 5 min 6 secs (still faster then a simple AO pass in MR):

http://www.redeyetales.com/forum/AO_VR_IM_3B_2m50s.jpg

Also, since people were asking if Vray was used in commercials, I saw this link of this websites page:

http://features.cgsociety.org/story_custom.php?story_id=3099&page=

[wurp]

First of all usually you cant mix rendering engines when the comp has to match up pixel-perfect, I've never tried but Im sure vray and mr has quite different AA on the edges so in a comp you would get "matte-lines" I've tried this with prman and MR and had lots of problems..

cpnichols: it seems you've not setup the occlusion pass correctly in mr, normally the area under the bridge would look more like the last vray picture you posted, as the occlusion shader just traces the distance to other objects that area would never be black as it is in your renders, also, there's a fair bit you can do to optimize the occlusion rendering, for example dont make the max tracedepth infinite, limit it as much as you like and you will see that the rendertime improves quite a lot.

[cpnichols]

First of all usually you cant mix rendering engines when the comp has to match up pixel-perfect, I've never tried but Im sure vray and mr has quite different AA on the edges so in a comp you would get "matte-lines" I've tried this with prman and MR and had lots of problems..

cpnichols: it seems you've not setup the occlusion pass correctly in mr, normally the area under the bridge would look more like the last vray picture you posted, as the occlusion shader just traces the distance to other objects that area would never be black as it is in your renders, also, there's a fair bit you can do to optimize the occlusion rendering, for example dont make the max tracedepth infinite, limit it as much as you like and you will see that the rendertime improves quite a lot.

Sure, you can't really mix renderign engines. Actually, you can if you are cleaver. ILM and others mix MR and renderman all the time.

I AM using the AO correctly. By limiting the distance of the rays, I would be cheating the occlusion in thinking there is nothing out there. This may be an advantage in speed, and may give you the result you want. On the other hand, I can take that ray, make it go even further, and actually bounce it off the next 3 surfaces collecting color along the way. I guess everyone seems to be missing my point that GI in Vray is fast enough that you don't need to use it for AO only.

Listen, if AO is part of your bag of tricks to fake the look of GI, that is fine. The question of this thread was:

Ambient Occlusion in Vray... is it possible? The answer I am giving is sure, but why limit yourself to AO when you can get GI for half the price.

[wurp]

You're not setting it up properly when it looks like that, heh, with a proper occlusion shader nothing will be black unless its really close to another object, and the underside of that bridge sure isnt...

Also, if you ever worked in production you'd know that cheating is more a rule rather than an exception, so cheating is fine as long as it still looks right. What makes occlusion so flexible is the fact that it can be used to cheat things and used in so many different ways, sure if you just wanna render pretty interiors vray might be good, and GI will work in some other cases as well, but if the GI solution doesnt look right its kind of hard to fix it afterwards as its "too accurate". If you're missing contact shadows somewhere you can render out a separate occlusion pass for just that part to darken it. Also, throwing in a skydome and enabling gi is NOT the same as occlusion, it might look similar for exterior scenes but the occlusion shader works in a different way.

as for mixing prman and mr, sure it can be done, for example rendering particles in prman and the rest in mr would work, but then you're not really bothered about matte-lines, that was my whole point..

[cpnichols]

You're not setting it up properly when it looks like that, heh, with a proper occlusion shader nothing will be black unless its really close to another object, and the underside of that bridge sure isnt...

Also, if you ever worked in production you'd know that cheating is more a rule rather than an exception, so cheating is fine as long as it still looks right. What makes occlusion so flexible is the fact that it can be used to cheat things and used in so many different ways, sure if you just wanna render pretty interiors vray might be good, and GI will work in some other cases as well, but if the GI solution doesnt look right its kind of hard to fix it afterwards as its "too accurate". If you're missing contact shadows somewhere you can render out a separate occlusion pass for just that part to darken it. Also, throwing in a skydome and enabling gi is NOT the same as occlusion, it might look similar for exterior scenes but the occlusion shader works in a different way.

as for mixing prman and mr, sure it can be done, for example rendering particles in prman and the rest in mr would work, but then you're not really bothered about matte-lines, that was my whole point..

Actually I have done plenty of production work, and am a senior technical director at a major VFX facility... Cheating always happens. In GI you can cheat as well. In the same way that photographer cheat when they take photos. There are also plenty of ways to "fix" what you would call "problems" in with a GI pipeline. I ran into lots of people that dismiss GI as fancy work done for ArchViz....

What you are calling AO where you only want the very close objects to occlude is also possible in Vray and is more appropriatly called a Dirt Shader.

I would encourage you to look into lighting with GI. The only problem is that you will have to relearn lighting. After a while you will see that it is just as flexible as anything else, and that you more limited by your creativity than coming up with solutions to make it look real.

Actually another way the people "mix" renderings sometimes is that MR is quicker then PRman at AO, so they render the AO pass in MR and project it back on the object in Prman. Actually a simplified explanation of something more complicated. Also, you could bake the AO as a texture.

[wurp]

I am using GI from time to time, just I dont think it fits in all situations, for complex stuff its either too slow or has other issues like flickering etc, also there are some issue rendering with GI on a farm, it can be sorted but usually its just a wast of time in my opinion.

anyway, both solutions has its ups and downs, but I think we are going to do things the "traditional" way for quite a few more years still..

[gent_k]

Can we settle in calling it an occlusion pass :-P

Anyway I usually use an occlusion pass solely for ground contact-shadows. This way I can get away with quick/rough FG settings that produce smooth shadows and lighting in a very short time, and the occlusion pass for finer contact shadows.

[cpnichols]

anyway, both solutions has its ups and downs, but I think we are going to do things the "traditional" way for quite a few more years still..

I'm going to agree with you for the most part on this.... but I would say a cinematographer is more "traditional" than a CG artist. Also, you don't see grips running out on stage with a can of black paint, painting contact shadows under peoples feet.

To be really honest with you Wurp... and maybe you agree with me on this... I'm just tired of lighting like a cg artist, I want to light like a cinemagrapher.... and AO is just not going to cut it. I need full GI.

[mr Bob]

So Christopher are you using Vray over at Sony Image works then , Sony's Maya renderman based isnt it ? and if you do you use it, Im interested in how it works within your pipeline.especially with the current projects sony has.

B

[cpnichols]

So Christopher are you using Vray over at Sony Image works then , Sony's Maya renderman based isnt it ? and if you do you use it, Im interested in how it works within your pipeline.especially with the current projects sony has.

B

Actually there are a few other tools that Sony uses, but no Vray is not used at Sony.

[dagon1978]

http://www.redeyetales.com/forum/AO_MR_8m19s.jpg


this is NOT an AO pass

try to learn mr before start talking of it ;)

[cpnichols]

this is NOT an AO pass

try to learn mr before start talking of it ;)

I would love to hear the reason why it is not an AO pass. I can set the distance to whatever I want, including infinity. The underside of the bridge IS occluded by the street below it when it comes to the ambient light. Sure it would be more practical to set it the distance of the ray to something that does not hit the street, but that is a cheated AO. You could call it AO if you want, and it may serve you well. I have been using AO passes in all sorts of rendering engines for years, including a simple AO pass, such as the one I did above, as well as ones where you can chance the distance and spread of the rays. I just find them obsolete if you can do GI.

Jezz... am I talking to thin air? Does nobody want to acknowledge that a GI pass may actually be better then an AO pass?

[dagon1978]

I would love to hear the reason why it is not an AO pass. I can set the distance to whatever I want, including infinity. The underside of the bridge IS occluded by the street below it when it comes to the ambient light. Sure it would be more practical to set it the distance of the ray to something that does not hit the street, but that is a cheated AO. You could call it AO if you want, and it may serve you well. I have been using AO passes in all sorts of rendering engines for years, including a simple AO pass, such as the one I did above, as well as ones where you can chance the distance and spread of the rays. I just find them obsolete if you can do GI.

Jezz... am I talking to thin air? Does nobody want to acknowledge that a GI pass may actually be better then an AO pass?

i'm thinking you have ever make an AO pass if you think that this is an AO pass
so, my question is... why do you want to use an AO pass like a GI pass?
1) you need an AO pass for the details, what kind of details you can see in your AO pass???
2) why an external render, try to make an interior render (with some light bounce) to see the difference about an AO pass and a GI pass
3) if u're unable to make a fastest render send me your scene and i made it for you ;)

[scottsch]

Here is an example of good Ambient Occlusion in mental ray with Jeremy Pronk's tolight shader:

http://www.thereisnoluck.com/images/toLight/occlusion_upper89.JPG

AO is supposed to be used in a composite to put shadow detail in specific areas - it's not supposed to be used to light an entire scene like global illumination.

People are pointing out that the bridge scene has characteristics of a diffuse lighting pass. If it was AO, the scene would be almost entirely white, especially the curbing which doesn't have anything near it which would put it in shadow.

I always thought an AO shader was used to fake GI. Now I see GI being used to fake AO. :cry:

[cpnichols]

i'm thinking you have ever make an AO pass if you think that this is an AO pass
so, my question is... why do you want to use an AO pass like a GI pass?
1) you need an AO pass for the details, what kind of details you can see in your AO pass???
2) why an external render, try to make an interior render (with some light bounce) to see the difference about an AO pass and a GI pass
3) if u're unable to make a fastest render send me your scene and i made it for you ;)

OK Dagon... I hope you don't take offense to this, but basically I have concluded that either you are not reading what I am trying to explain, or you just have a poor understanding or English. If it is the the second one, I am sorry. I decided to explain it with some more pictures. Yes, indeed the AO pass on MR is faster if we shorten the ray distance. Just to prove to use that I DO know what an AO pass is, I can do one with a shorter ray distance for you:

http://www.redeyetales.com/forum/AO2_MR.jpg

On the other hand, this would be the output with the raw GI pass. You multiply this instead of your AO pass, you get much better results. At least that is my argument.

http://www.redeyetales.com/forum/GI_Vray_02.jpg

I hope this is enough to prove to you that I DO know what an AO pass is. I am just arguing that the GI is more useful, and more accurate. I really can't explain it any further. I do know that this is a hard argment for many people, as there are people that still use AO when doing GI. This is mostly done to simulate dirt.

If you would like to get a hold of the scene for you to try out. You can get it off of this DVD:

http://www.thegnomonworkshop.com/dvds/cni01.html

[dagon1978]

"One GI frame in Vray is faster then one AO frame in something else."

have u write something like this? did u remember?

and this render, for you, demonstrates this affirmation??

but your render is'nt an usable AO pass!!

if u want to demonstrates that an AO pass is less accurete than a GI pass... sorry, but i think isn't a great discovery :rolleyes:

[dagon1978]

Here is an example of good Ambient Occlusion in mental ray with Jeremy Pronk's tolight shader:

http://www.thereisnoluck.com/images/toLight/occlusion_upper89.JPG

AO is supposed to be used in a composite to put shadow detail in specific areas - it's not supposed to be used to light an entire scene like global illumination.

People are pointing out that the bridge scene has characteristics of a diffuse lighting pass. If it was AO, the scene would be almost entirely white, especially the curbing which doesn't have anything near it which would put it in shadow.

I always thought an AO shader was used to fake GI. Now I see GI being used to fake AO. :cry:

yeah! this is an AO pass!!
but... isn't accurete! :p try with vray, it's faster! :D

[cpnichols]

"One GI frame in Vray is faster then one AO frame in something else."

have u write something like this? did u remember?

and this render, for you, demonstrates this affirmation??

but your render is'nt an usable AO pass!!

if u want to demonstrates that an AO pass is less accurete than a GI pass... sorry, but i think isn't a great discovery :rolleyes:

Sorry... I have a hard time understanding what you are trying to say. Your english is simply too poor. Which leads me to believe that you are more interested in trying to proove me wrong than actually have a conversation. It was fun talking to you nonetheless.... have a great day.

[dagon1978]

Sorry... I have a hard time understanding what you are trying to say. Your english is simply too poor. Which leads me to believe that you are more interested in trying to proove me wrong than actually have a conversation. It was fun talking to you nonetheless.... have a great day.
ehehe u have understood, i think ;)

bye bye

[mr Bob]

I certainly am interested in the merits of either way of doing things.So currently from a film compositing point of view an AO pass is very fast in MR or Renderman and currently we bake the AO pass into out objects with textures.
Now what I really want to know is Obviously you can drive a very fast GI pass using vray, so if your not using vray at Sony Image works , that would tend to mean your using renderman or a in house renderman complient render engine, if that is the case have you written in house tools that can do the vray style of GI/AO pass for compositing.
So how does this affect your day to day work using tools other than vray and how do you get the results your after ....Ive seen "vendor" tests in the past and the quality blew me away...

B

[Wiro]

Dagon1978, please keep it civil. Your remarks verge on trolling.

Look closer at the AO bridge pictures. The one with the long rays catches the bridge shadows on the highway but misses everything under the bridge. The one with the short rays which you say is a more correct AO pass does get the fine detail under the bridge but misses the groundplane, causing no shadow from the bridge on the road.

In other words it's obviously an incorrect representation of how light would work. What cpnichols is saying is that you may as well use a proper VRay skylight with bounces for roughly the same rendertime and get it all correct. I don't know why you are trying to discredit him for that.

Now on the other hand, if this was an interior scene with walls and ceiling there would obviously be no skylight. Interior GI bounces are far slower to compute and here an AO pass would be much faster.

Wiro

[dagon1978]

Dagon1978, please keep it civil. Your remarks verge on trolling.

Look closer at the AO bridge pictures. The one with the long rays catches the bridge shadows on the highway but misses everything under the bridge. The one with the short rays which you say is a more correct AO pass does get the fine detail under the bridge but misses the groundplane, causing no shadow from the bridge on the road.

In other words it's obviously an incorrect representation of how light would work. What cpnichols is saying is that you may as well use a proper VRay skylight with bounces for roughly the same rendertime and get it all correct. I don't know why you are trying to discredit him for that.

Now on the other hand, if this was an interior scene with walls and ceiling there would obviously be no skylight. Interior GI bounces are far slower to compute and here an AO pass would be much faster.

Wiro

this is a troll statement for me

"One GI frame in Vray is faster then one AO frame in something else"

isn't it? :thumbsup:

[Wiro]

It's a broad and probably incorrect statement which you are free to challenge as long as you keep it respectful and that doesn't only mean putting a smiley at the end of your post.

Wiro

[dagon1978]

It's a broad and probably incorrect statement which you are free to challenge as long as you keep it respectful and that doesn't only mean putting a smiley at the end of your post.

Wiro

yeah, probably ;)
and I've been probably too much sarcastic in my answers, sorry

ciau

mat

[cpnichols]

I certainly am interested in the merits of either way of doing things.So currently from a film compositing point of view an AO pass is very fast in MR or Renderman and currently we bake the AO pass into out objects with textures.
Now what I really want to know is Obviously you can drive a very fast GI pass using vray, so if your not using vray at Sony Image works , that would tend to mean your using renderman or a in house renderman complient render engine, if that is the case have you written in house tools that can do the vray style of GI/AO pass for compositing.
So how does this affect your day to day work using tools other than vray and how do you get the results your after ....Ive seen "vendor" tests in the past and the quality blew me away...

B

Sorry... I am not really at liberty to talk about the details of where I work. But I can tell you, that personally, GI has been part of what I am interested in for the last 6 years. AO was clever when I first saw it appeared on Pearl Harbor... and it is amazing that it is still used to this day. But my prediction is that it will eventually be replaced by full GI.

[cpnichols]

yeah, probably ;)
and I've been probably too much sarcastic in my answers, sorry

ciau

mat

Thanks Dagon. I will give you this... as you know, as you are probably a big MR user, and it is very easy to make a raytracer very slow by changing a few settings. So any statement (such as the one I made), where someone says my rendering engine is faster then your must always be taken with a grain of salt (an English expression meaning not very seriously). But, the basic point I wanted to make is that GI is very fast in Vray and that it is luxury that people can start to afford. If we look back to the beginning of this thread :) all I wanted to do is encourage someone not to limit themselves to AO in terms of Vray.

[metamesh]

hi
forgive my stupidity all of you people but i still don't understand why do u wanna use the AO thing...isn't that suposed to be a way to fake GI? so why do u wanna fake it if u can do it with real GI for the same amount of time? a close friend was trying to tell me that the cool thing is to have the GI pass and then add a pass of AO but that just looks like a dirty map to me...am i wrong? thanks! btw i find vray quite incredible too

[percydaman]

I see nothing wrong with using a dirt pass in certain situations in addition to your GI.

[metamesh]

i know, i didn´t say that it´s wroong to do that, i´m just asking if at the end of the day, the AO is just to do a "dirty" effect in ur render?

[cpnichols]

I agree... but that is why people call it a dirt pass and not an AO pass, even if those two passes share a lot of similarities.

[Hee]

http://www.geocities.com/digisun2000/problem/problem1.jpg
I am new to Vray. Can anyone tell me how I can fix the noise problem?
I really appreacite your help.

[tweeeker]

i know, i didn´t say that it´s wroong to do that, i´m just asking if at the end of the day, the AO is just to do a "dirty" effect in ur render?

Not really, in general occlusion is used for a lot more than a 'dirty effect' (which can usually be executed better with properly painted textue maps)

Many people use an occlusion pass in a composite by multiplying the entire render with the occlusion. Doing this is going to offer up something that does look like dirt (that's not meant to sound sarcastic:)), which is perhaps where the name comes from. In shading terms this is a bit of an odd thing to do because the specular/diffuse combo of the shader is ignored as is the ratio of direct/ambient light.

Alternatively, the occlusion pass can be used to only attenuate ambient light, which results in an effect that looks much more like shadowing than dirt. This is how occlusion was first put to use in films such as pearl harbour.

As far as occlusion vs gi is concerned I think its important to clarify again that the requirements for each are quite different, and the strengths and weaknesses of each better suited to certain applications. The bottom line is GI isn't much use if theres nothing to bounce rays off (e.g integrating with live action). On the other hand AO isn't much use if it offers a poor approximation of incoming light (e.g complex interiors). However in circumstances where ambient occlusion DOES give a good approximation (e.g small object in huge environment) AND there's nothing to bounce off anyway, it can be an invaluable technique (again, pearl harbour springs to mind)

Overall I agree with cpnichols tho - if GI is an appropriate option for the task at hand and your renderer is quick enough, I guess there's little point in approximating with AO.

T

[cpnichols]

I think that if you read through the last 4 pages of this thread, you will notice that this subject has been well discussed, debated, etc...

[percydaman]

I think that if you read through the last 4 pages of this thread, you will notice that this subject has been well discussed, debated, etc...

huh?


whats the point of THAT post?

[mr Bob]

I would be interested to see what film pipelines have used a GI render at 2k for a job , all Ive ever seen is AO passes used , then again Ive never come accross a film pipeline using max and vray its all been renderman and maya,from this discussion I shall be looking at your dvd mr Nichols next week.....

B

[tweeeker]

I think that if you read through the last 4 pages of this thread, you will notice that this subject has been well discussed, debated, etc...

Hmm, I have to disagree with 'well' discussed. Most of this thread has been concerned with splitting hairs over what is, and what isn't AO. I guess that's why after 5 pages someone can still go "AO is just to do a "dirty" effect in ur render"

I was simply trying put forward my thoughts on the pros of cons of each, because as this thread proves, theres still a fair amount of confusion/misunderstanding.

Anyways, sorry for wasting anyones time...

T

[cpnichols]

I would be interested to see what film pipelines have used a GI render at 2k for a job , all Ive ever seen is AO passes used , then again Ive never come accross a film pipeline using max and vray its all been renderman and maya,from this discussion I shall be looking at your dvd mr Nichols next week.....

B

Actually, GI has been used on many films. Mostly feature animations. The Incredibles used Brazil for certains shots. I am pretty sure that Blue Sky used a lot of GI on Robots, and lets not forget Shrek 2. The Orphanage uses Brazil a lot these days. Pretty sure they used some GI on the sections that they worked on of Day After Tomorrow.

[Omega Productions]

cpnichols : Thanks so much for making that V-Ray dvd. I was an avid V-Ray user for along time I thought I was getting some pretty good results. After seeing it in the hands of someone like yourself it is just amazing! :)

[kcott]

i just want to say thanks to cpnicholds, wiro, and wurp. i never really understood AO and now i have a better understanding of it. this forum is great thanks to people like you that share.

keith

[TiskO]

Chris, i just saw that you have your own gnomon dvd. I might buy to see what wlse i might learn. Cant wait!

[playmesumch00ns]

Actually, GI has been used on many films. Mostly feature animations. The Incredibles used Brazil for certains shots. I am pretty sure that Blue Sky used a lot of GI on Robots, and lets not forget Shrek 2. The Orphanage uses Brazil a lot these days. Pretty sure they used some GI on the sections that they worked on of Day After Tomorrow.

Incredibles used GI on some matte paintings. I'm pretty sure blue sky did not use full gi on robots, using traditional lighting and AO instead. Shrek 2 used a clever approximation that was remapped onto the final render geometry.

I still think it will be a while before we see "full" GI being recalculated each frame for a final-frame render, probably about the same time as 64-bit machines become prevalent.

Even then, I'm currently using an approximation technique to get a very close to a correct diffuse interreflection solution in a fraction of the time it takes to calculate "real" GI. I imagine that I'll still be using that rather than GI in a couple of years, just because it's so fast and will benefit from the increased memory limits on 64-bit.

[kissb]

ILM used GI when they made sunny for lemony snicket, but only 1 bounce ( cinefx no100, lemony snicket extra dvd )

[playmesumch00ns]

But did they say how they did it?

Actually just to contradict myself I wouldn't be surprised if they were rendering GI passes in mental ray for lots of things.

I wouldn't be surprised either if they had a huge 64-bit renderfarm to do it on. For the rest of us tho...

[a23]

But did they say how they did it?

Actually just to contradict myself I wouldn't be surprised if they were rendering GI passes in mental ray for lots of things.

I wouldn't be surprised either if they had a huge 64-bit renderfarm to do it on. For the rest of us tho...

Hi there playmesumch00ns,

maybe this helps, but you have probably read that before:

http://www.panoscan.com/PanoPress/2005Press/Lemony/LemonySnicket.html

Cheers, AndY

[tweeeker]

Thats a cool article. Now if only cinefex were like that...

TBH the results from prmans gi are pretty good, just that it takes an age. But then I guess ILM probably aren't to fussed at 10+ hours a frame for GI. B******s

T

[playmesumch00ns]

Global illumination is slow because you’re bouncing light, so we decoupled it, simplified the model, and used fewer points for this point cloud,” Hery says. Also to speed the process, the illumination was calculated using one bounce. The data that resulted was fed into the higher resolution point cloud as one component of the lighting used for subsurface scattering on Sunny’s skin

It's this part that's interesting... trouble with these articles is they never go into the details you want them to!

Sounds like they're using low-res geometry with a higher shading rate, baking this and then remapping it onto the render geometry, which is basically what dreamworks did for shrek 2...

I'd be very interested to know some more details.

tweeker: prman's actually quite a fast raytracer; it's just the shading that takes so long. Hopefully they'll fix this in the next version.

[tweeeker]

prman's actually quite a fast raytracer; it's just the shading that takes so long. Hopefully they'll fix this in the next version.

Tell me about it, thats what I was refering too - the long shader initializations that are currently a pain in the ass. Ambient Occlusion on the other hand is nice and fast... hmm I could have sworn there was a thread somewhere about that:)

T

[tweeeker]

Sounds like they're using low-res geometry with a higher shading rate, baking this and then remapping it onto the render geometry, which is basically what dreamworks did for shrek 2...

Yes, although I'm not sure if they mean they simplified the 'lighting model' or the 'geometry model'. Perhaps just the environment was lowres/high shading rate while the baby to baby bounces were done on the hi-res. The indirectdiffuse function interpolates anyway, so you don't usually gain that much from a higher shading rate (unless you've turned interpolation off of course - which is quite likely).

[Wiro]

Not sure I understand what "using low-res geometry with a higher shading rate, baking this and then remapping it onto the render geometry" means in terms of VRay but isn't this something similar to undersampling GI?

Wiro

[Saturn]

it like processing your vrmap on Low res geometry and use it on higher geometry

[playmesumch00ns]

Tell me about it, thats what I was refering too - the long shader initializations that are currently a pain in the ass. Ambient Occlusion on the other hand is nice and fast... hmm I could have sworn there was a thread somewhere about that:)

Fancy that: all those lovely output variables are causing it to grind to a halt!

The context of the sentence before makes me think he's talking about the geometry in that quote, but I'm sure he's talking about the lighting model as well.

I would imagine they baked the bounce into texture- or brick-maps in a pre-pass using very simple shaders and simplified geometry, then looked these up in the final render.

[percydaman]

BTW the dirtshader for vray is wicked. ALOT faster and easier to adjust then mentalray.

[wurp]

How can it be easier to adjust? If you're talking about dirtmap for mr it has about 4 parameters to tweak, heh, how can it be any easier...


BTW the dirtshader for vray is wicked. ALOT faster and easier to adjust then mentalray.

[percydaman]

How can it be easier to adjust? If you're talking about dirtmap for mr it has about 4 parameters to tweak, heh, how can it be any easier...

well I tried the dirtshader for MR. And I just couldn't get it to work right. Im sure it was me.

[dagon1978]

BTW the dirtshader for vray is wicked. ALOT faster and easier to adjust then mentalray.

lol

u have forgotten: "vray rulez"

:banghead:

but, why do u wanna use AO in vray?? use the fassst GI!

[+disciple+]

lol

u have forgotten: "vray rulez"

:banghead:

but, why do u wanna use AO in vray?? use the fassst GI!


Your a trouble maker. If I was your boss I'de put you on vertex detail, you little freak

[dagon1978]

Your a trouble maker. If I was your boss I'de put you on vertex detail, you little freak

ALOT faster and easier to adjust then mentalray?

:rolleyes:

[kissb]

relax dagon :)
What was the problem percydaman?You have to push your mouse button 4 times(or less).You can't screw it, even if you want :)
You can render the occlusion and the environment as well, also the bent normals, if you want to use it in shake or whatever...

[cpnichols]

relax dagon :)
What was the problem percydaman?You have to push your mouse button 4 times(or less).You can't screw it, even if you want :)
You can render the occlusion and the environment as well, also the bent normals, if you want to use it in shake or whatever...

The dirt shader in Vray is essentially the same as mental ray. Environment and bent normal passes in Vray can automatically be created with the gbuffer.

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