Re: Mental Ray render settings was "Re: shadow flicker"
| Date : Tue, 6 Jun 2006 10:56:31 +0200 |
| To : <XSI(at)Softimage.COM> |
| From : "Tim Leydecker" <BauerOink(at)gmx.de> |
| Subject : Re: Mental Ray render settings was "Re: shadow flicker" |
Ok, this takes us absolutely nowhere, either you don't want to understand that both of us talk about the very same thing or my english simply is too bad to make people understand what I'm talking about. Anyhow, I'm off this thread now, there's everything said and repeated at least once.
Butting into this thread for being an expert at misreading the intended tonality of a post and also being gifted with a most natural talent to stir things up in a somewhat disturbing way:
"...Mitchell filtering, which in most setups needs higher radii to create nice-looking imagary, many more samples are taken into consideration for a single pixel's colour value...."
indeed you did...
I´d say Steve just wanted to admit he had missed that bit in your previous post and even had the balls to do it in public. One could find a trace of sarcasm in it if it where written in german but I think it isn´t meant to be taken that way - as it´s not written in german...
"Ja, und?"
"Oder was?"
Cheers
tim
----- Original Message ----- From: "André Adam" <a_adam(at)49games.de>
To: <XSI(at)Softimage.COM>
Sent: Tuesday, June 06, 2006 10:18 AM
Subject: Re: Mental Ray render settings was "Re: shadow flicker"
Ok, this takes us absolutely nowhere, either you don't want to understand that both of us talk about the very same thing or my english simply is too bad to make people understand what I'm talking about. Anyhow, I'm off this thread now, there's everything said and repeated at least once.
Steven Caron wrote:
"...Mitchell filtering, which in most setups needs higher radii to create nice-looking imagary, many more samples are taken into consideration for a single pixel's colour value...."
indeed you did...
On 6/5/06, *André Adam* <a_adam(at)49games.de <mailto:a_adam(at)49games.de>> wrote:
"filtering doesn't decide how many samples are taken..."
Hey Steven, that's exactly what I've said, reread my mails. However, the filter size *does* decide on how many samples will be combined for a single pixel *after* all rays are shot by creating an ellipse around the center of that pixel and collecting all the samples within the given x/y radii. Your observations regarding the eye-rays are interesting, though. We seem to have a few extra rays in there, but I see the basic idea of samples = pixels with a sampling value of 0 still being valid, don't you think? At least I can live with a variance of less than ten percent... ;)
Steven Caron wrote:
> /deep breath! > > /filtering doesn't decide how many samples are taken... > > file:///C:/Softimage/XSI_5.0/Doc/mental_ray/manual/node76.html#INDEX188 > > "...The *filter* statement specifies how multiple samples are to be > combined into a single pixel value..." > > and if you just take look at jitter thats only two definitions down > from filter... > > "...Without *jittering*, samples are taken at the corners of pixels or > subpixels..." > > and if you turn jitter on. with AA min 0 and max 0... mental ray > kindly turns jitter off :) why? Because it will introduce artifacts > with that low of a sampling rate... > > //INFO : RC 0.2 warn 082008: jittering disabled because max > samples < 1 > > So according to you a 100 x 100 render would produce 10000 samples? ( > eye rays ) Lets test this! > > I setup a format of... 100 x 100. AA min of 0 and max of 0. Jitter > OFF. Threshold rgba to 1.0 and filter type box 1 1, but threshold > doesn't matter because of min and max samples being the same and > filter doesn't matter because it only averages samples already taken. > > turn progress on... > //INFO : RC 0.2 info : rendering statistics > //INFO : RC 0.2 info : type number per > eye ray > //INFO : RC 0.2 info : eye rays > 10816 1.00 > > hmmm interesting! > > I am going to throw another variable in here... task size or tile > size. this option will really increase or decrease your samples... > smaller task size is going to give you more samples.. larger is going > to give you less. Here is a quick formula for predicting samples. I > say predicting, because there is no way to know everything they are > doing internally, short of being a mental images developer. > > task size + 1 * task size + 1 = samples per tile... > > To test this make a 32 x 32 resolution AA min 0 max 0 and turn your > "tile size" to 32x32. You can leave automatic in cause most likely > mental ray will choose this, but just in case force it. you know so > you feel like your in control. You will get... > > 32 + 1 * 32 + 1 = 1089 > > have fun.. do some more tests... > > André Adam wrote: > >> To add to this, the position sampled is only important for the >> filtering algorithm that collects samples using a specific radius >> around the center of the pixel. With an aa setting of 0 and a box >> filter with a size of 1, indeed four samples will be considered to >> retrieve the final colour value for this pixel. However, hardly >> anyone uses a box 1/1 filter. When switching to the more popular >> Mitchell filtering, which in most setups needs higher radii to create >> nice-looking imagary, many more samples are taken into consideration >> for a single pixel's colour value. However, the sample density shot >> by the renderer *does not* increase in this scenario, with aa 0 it >> stays one sample shot per pixel. >> >> >> André Adam wrote: >> >>> Nope, with aa 0 you get exactly as many samples as you have pixels >>> for the whole image. It definately is one sample per pixel. Not >>> centered, but that doesn't make much of a difference, the spacing >>> between the samples stays one pixel regardless of the position >>> sampled. It's just about offsetting the sampling raster. Which btw >>> gets randomised anyways when enabling the sample jitter option. >>> >>> Cheers! >>> >>> -André >>> >>> >>> Steven Caron wrote: >>> >>>> "...and one sample per pixel (aa setting 0)..." >>>> >>>> just like bernard and kim said about threshold being misunderstood >>>> this too is misunderstood. >>>> >>>> mental ray samples at the corners of a pixel. meaning 4 per pixel >>>> not 1. but not always 4 new samples because mental ray can share >>>> samples with bordering pixels. >>>> >>>> *bracing myself now* >>>> >>>> steven >>>> >>>> On 6/2/06, *André Adam* <a_adam(at)49games.de <mailto:a_adam(at)49games.de> >>>> <mailto:a_adam(at)49games.de <mailto:a_adam(at)49games.de>>> wrote: >>>> >>>> A really nice example covering this problem is a hemisphere mapped >>>> with >>>> a clear night sky showing lots of small stars. If the min aa >>>> setting is >>>> too broad (and one sample per pixel (aa setting 0) might very >>>> well be >>>> too broad), the rays will likely completely miss out certain >>>> stars on >>>> certain frames which leads to the stars wildly flickering in >>>> animation... >>>> >>>> >>>> kim aldis wrote: >>>> >>>> >I'm not trying to put you down here Bernard but there are >>>> situations where >>>> >settings like this aren't good and you should have some idea of >>>> what sort of >>>> >image you're rendering before making decisions about aa settings. >>>> In some >>>> >shots, messing with threshold won't make any difference at all, >>>> raising max >>>> >settings will make little difference unless you bring up the min >>>> settings. >>>> >You're right, threshold is largely misunderstood. Let's try and >>>> shed some >>>> >light:- >>>> > >>>> >here's something you can try. Get a cube, unit 1. scale it so >>>> it's really >>>> >long and really thin - 0.02, 0.02, 35. >>>> >now duplicate it 20 or 30 times and space each cube one unit >>>> apart in x. Now >>>> >shift them all back away from the camera so you get a good >>>> convergance. Lots >>>> >of thin, parallel lines in the distance, all converging to the >>>> vanishing >>>> >point is what you're looking for. >>>> > >>>> >Now mess with the aa settings and pay close attention to the >>>> quality where >>>> >the cubes are nearly converging. Try 0,3 and mess with the >>>> threshold. Not a >>>> >lot of difference, is there, even if you set the threshold really >>>> as low as >>>> >you can get it. In fact, changing the threshold varies not a lot >>>> at all. >>>> > >>>> >now compare 0,2 with 0,3. Not much better. And I'll bet if you >>>> try 1,2 it'll >>>> >be way better than 0,3. Again, regardless of the threshold. >>>> > >>>> >The point here is that there's a real danger of getting it wrong >>>> if you >>>> >start generalising aa settings and don't take into account the >>>> kind of image >>>> >you're rendering, as Helen is finding out, since sampling grain >>>> is fine >>>> >detail. I just tried something here. Pushing aliaising to 1,2 >>>> with default >>>> >threshold gave me better improvement than doubling the >>>> sampling size. >>>> >lowering the threshold improved things a bit but nothing worked >>>> better - nor >>>> >was faster - than raising the min setting, bringing it closer to >>>> the max. >>>> > >>>> >If you really want to see how well - or otherwise - aa is >>>> working, turn on >>>> >'view sampling' in the region diagnostic tab. It's most >>>> revealing. >>>> > >>>> >-----Original Message----- >>>> >From: owner-xsi(at)Softimage.COM <mailto:owner-xsi(at)Softimage.COM> <mailto:owner-xsi(at)Softimage.COM <mailto:owner-xsi(at)Softimage.COM>> >>>> [mailto: owner-xsi(at)Softimage.COM <mailto:owner-xsi(at)Softimage.COM> <mailto:owner-xsi(at)Softimage.COM <mailto:owner-xsi(at)Softimage.COM>>] >>>> On Behalf Of >>>> >Bernard Lebel >>>> >Sent: 01 June 2006 16:23 >>>> >To: XSI(at)Softimage.COM <mailto:XSI(at)Softimage.COM> <mailto:XSI(at)Softimage.COM <mailto:XSI(at)Softimage.COM>> >>>> >Subject: Re: shadow flicker >>>> > >>>> >I would definitely use a min of 0 and a max of 3. >>>> > >>>> >Also, what is generally ignored or misunderstood is the treshold. >>>> The >>>> >treshold color is a control for how sampling is done. Lower >>>> values means >>>> >that sampling occurs with lower contrasts, in other words, the >>>> level of >>>> >sampling have more chances of getting closer to the max value. >>>> Higher >>>> >treshold means a higher contrasts is tolerated before requiring >>>> another >>>> >level of sampling, so less samples may be takne. >>>> > >>>> >I never work with treshold higher than 0.05, and had to go as >>>> low as >>>> >0.005 on few occasions. Note that at that point, if the image is >>>> detailed, >>>> >you should consider ignoring adaptive sampling altogether and use >>>> same min >>>> >and max values. If the image has significant amounts of constant >>>> colors >>>> >(like shadow passes, black backgrounds in the likes), then >>>> adapative >>>> >sampling is still a viable solution. >>>> > >>>> > >>>> >Lastly, my rule of thumb for the filtering is Gaussian 3/3 for TV >>>> output and >>>> >Mitchell 4/4 for film output. Gaussian gives a blurrier sample >>>> >interpolation, which may "conceal" minor imperfections. >>>> > >>>> > >>>> > >>>> >Cheers >>>> >Bernard >>>> > >>>> > >>>> > >>>> > >>>> >On 6/1/06, Helen Bucknall <helen(at)helenbucknall.com <mailto:helen(at)helenbucknall.com> >>>> <mailto: helen(at)helenbucknall.com <mailto:helen(at)helenbucknall.com>>> wrote: >>>> > >>>> > >>>> >>Mostly I just use min -1 and max 2. and box filtering 1 or >>>> sometimes I >>>> >>use triangle 2 for a softer effect. >>>> >> >>>> >>I output a string of 852 x 480 bmps to my clients and then >>>> they mpeg >>>> >>it somehow and wack it up on big plasma screens. They never >>>> complain. >>>> >>When they want stills for print I just render a frame out huge >>>> >>(3000+)but leave the antialiasing the same. >>>> >>If it's for telly I do HD res. If it's to be comped with live >>>> action I >>>> >>ask what anti aliasing they want. >>>> >> >>>> >> >>>> >> >>>> >>Bernard Lebel wrote: >>>> >> >>>> >> >>>> >> >>>> >>>Samples 20 is a bit low. I generally put 64 as soon as I set >>>> up the >>>> >>>shadow map. >>>> >>> >>>> >>>What do you mean with "standard antialiasing"? >>>> >>> >>>> >>> >>>> >>>Bernard >>>> >>> >>>> >>> >>>> >>> >>>> >>> >>>> >>>On 5/31/06, Helen Bucknall <helen(at)helenbucknall.com <mailto:helen(at)helenbucknall.com> >>>> <mailto:helen(at)helenbucknall.com <mailto:helen(at)helenbucknall.com>>> wrote: >>>> >>> >>>> >>> >>>> >>> >>>> >>>>OK. I dragged the spotlight in closer to the scene elements >>>> and it >>>> >>>>seems to have stopped all the flickering! It wasn't that far >>>> away, >>>> >>>>but now it is almost close enough to make my character >>>> sweaty. I >>>> >>>>also scaled down my ground plane a tad. >>>> >>>> >>>> >>>>Just using 1024 res and sample 20. And bog standard >>>> antialiasing. >>>> >>>> >>>> >>>>So very BIG THANKS to all who replied! >>>> >>>> >>>> >>>>Joe Laffey wrote: >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>>>On Wed, 31 May 2006, Helen Bucknall wrote: >>>> >>>>> >>>> >>>>> >>>> >>>>> >>>> >>>>>>Is there a way to get shadow map shadows to stop >>>> flickering even >>>> >>>>>>when nothing is moving? >>>> >>>>>> >>>> >>>>>>This is what I have tried to no avail. >>>> >>>>>> >>>> >>>>>>On the spot light (cone angle less than 90): >>>> >>>>>>Resolution up ( and down). >>>> >>>>>>Softness up and down. >>>> >>>>>>Samples up. >>>> >>>>>> >>>> >>>>>>None of these make any diference to the flickering. >>>> >>>>>> >>>> >>>>>>On the render panel: >>>> >>>>>>I've played around with the antialiasing and jitter. >>>> >>>>>>On the shadows page I've clicked off rebuild. >>>> >>>>>> >>>> >>>>>> >>>> >>>>> >>>> >>>>>If you view your scene from the light is there an >>>> extremely large >>>> >>>>>depth to the objects? In other words, are the closest >>>> object to >>>> >>>>>the light and the farthest object from the light extremely >>>> far >>>> >>>>>apart? This can lead to ZDepth (used for shadowmaps) >>>> presision >>>> >>>>>issues in some renderers. >>>> >>>>> >>>> >>>>>This is often the case if you have a huge ground plane. >>>> >>>>> >>>> >>>>>You may be able to exclude some objects, to help, or make >>>> smaller >>>> >>>>>versions that catch shadows. >>>> >>>>> >>>> >>>>>-- >>>> >>>>>Joe Laffey | Visual Effects for Film and >>>> Video >>>> >>>>>LAFFEY Computer Imaging | >>>> ------------------------------------- >>>> >>>>>St. Louis, MO | Show Reel >>>> http://LAFFEY.tv/?e01274 >>>> >>>>>USA >>>> >>>>> >>>
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