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Saludos amigo hace poco me sucedio lo mismo con una imàgen, al momento de tirar el render 

me sacaba del programa, empece a indagar y al cambiar la configuraciòn del driver del

OpenGL a Direct 3D me dejo trabajar y sacar la imàgen a un excelente tamaño. Prueben a ver si tambien les resulta

Users of other apps/renderers, I am starting to put pertinent info at the bottom of the page

Have you ever wondered why your GI renderings start out so dark? Well, in fact theyare not so dark. The problem lies with the display device (the CRT or LCD) and that thesoftware is not making adjustments for the gamma that the displays put on our images.

That gamma is specifically called �sRGB . Technical information about sRGB can befound at that site.

Let's take a look at what your monitor does to image data you send it. This is callednon-linear a display. The spotted green line here is the data you are feeding the displayand the solid green line is what response the monitor has normally.

What's important to note here is that this correction is not just for filmic response. Infact, it has almost nothing to do with filmic response. It's essentially correcting for thedisplay. Those of you working for video (aka not film) don't worry. This applies to youas well. The rec.709 curve is -very- similar in nature.

Ok, that's nice and all but now you want to know how to solve this problem. Yes, it's a problem :) Well, friends, we apply a curve that takes the data and "linearizes" it. That

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means we negate what the monitor does. Here is the curve. Once again, the spotted lineis the data we are sending to the display. The solid line, this time, is the correction that'smade for the non-linear display.

To explain a bit further...sRGB is the correction your software makes for the non-linear response that your monitor has. Your digital camera applies an sRGB lookup to your 

 photographs but you may not even know it. So, when you work in true linear space youare actually working in a space that represents more what light does in the real world.Let's show you what I mean by that with yet more graphs but with a gradient this time.

This is a 0 to 1 ramp with 32 steps. Notice the 0.5 value is in the middle. This is theoriginal image data as sent to your monitor. This is a linear image!

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This is what your monitor does to the image. The .5 we had before is certainly not .5anymore. This is your non-linear monitor.

This is the correction we put on our viewing system to correct for the monitor's display.Yes it's much brighter. However, this is needed to correct for image #2 which makes thedisplay turn your gradient back into the original linear image.Hopefully that makes a bit more sense

Keeping on with the flow of information, check out another test to show you what linear is all about.

Here are two images. The grey swatch in the center or each image has a value of .18(the mid grey point) in the 3D app. The one on the left is gamma encoded to sRGB,where the one on the right is linearized via the sRGB monitor correction. This turns thegrey into .46 which is the spec for sRGB.

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Gamma Encoded image Notice the total lack of shadow detail

Linearized Image Notice the amount of detail we gain!

If you want to get a copy of the max file (it's using vray but doesn't require it) go here:sRGB_Linear_demo.zip

Let's get into the meat of the 3D app in question : 3DS Max 7.0 and VRay 1.46.xx.

For this example I have provided a scene that I used for testing : linear_demo.zip

Here is a scene prepped for Brazil by Rune Spaans : linear_demo_brazil.zip

You will need the �Greeble plugin to properly open this scene.

The first result we get from this render is so:

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 Now, we must linearize this image if we are to get more of a photographic response.

What am I talking about? Well, look at the amount of light hitting those objects. Itseems that with 1000 GI bounces that we'd see a bit more detail right?!? YES! Let's get

to that stage now.

First go to Customize -> Preferences -> Gamma tab and change the values to:

This allows us to see correct linear values in the material editor and the original maxrender view.

* Brazil users, you're pretty much done. Go to the end of this page for the rest of theBrazil settings.* Mental Ray users - you are done! Now you're working in a more correct linear method.* Scanline render users - you are also done. You're linear all the way now.

 Now, for the VRay part, go to the VRay renderer menu and in the Frame Buffer rollout

change a few things:

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Why did we do this? Well, the VRay vfb allows us to do some post render color correction to the image. Thanks to Vlado and the rest of the dev team for these changes!

 Next be sure to turn off any color clamping in the GBuffer/Color Mapping rollout:

 Now, do a quick render to get your VRay vfb up. Once you do we need to turn on a fewthings.

First, click on the curve correction and then open the color correction panel

The basic color correction panel looks like this. We'll be changing that of course...

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Start by right clicking on the lower point of the curve and pick the bezier smooth option

 Now, drag the tangent point to where is indicated here. Important!!! Make sure your numbers at the top read like what I have.

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Right click on the high point of the curve and change it to reset tangents.

This may not be exactly the correction for sRGB but it's pretty darn close.

 Now look at your image:

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What we've done is apply the correction for sRGB on your image (aka we've linearizedthe image). The viewer is doing this because that's its job. This is a linear response andalso shows the HUGE amount of detail truly visible in this render.

We are now looking at an image that is perceptually linear. You'll notice that withouttons of multiplying of the colors using the Color Mapping option we get a lot of detailin the dark areas.

So, there you go. Working in linear space means that you get a more realistic look andthat your lighting will actually be more correct and true to what a real camera does. Thisshould allow you to achieve your desired results with more ease and possibly faster render times too.

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Other Apps Info

Maya / Mental RayFor you Mental Ray/Maya users, go to the Render Globals and click the mental ray tab.Go to Framebuffer Attributes and change a few things:

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BrazilIn the Brazil render settings, go to the General Ottions rollout and make sure your setting match this

 Now, inside the vfb, open up the exposure/color panelSet the gamma to 2.2

In March 2004, Rob Nederhorst posted an  interesting thread on the support

forum of Vray and a couple of other forums about working in linear space.

 Although the thread answered a couple of questions it also generated a lot of 

questions and confusion about this workflow. In the following article, I have tried

to summarize these as well as take away any doubt people might have after

reading the article. I have written it in interview style, which I hope, makes it

 better readible.

O.K., I calibrated my monitor with a hardware calibrator, selected a gamma of 2.2and a whitepoint of 6500K. Now the article suggest to do the gamma correction in 3dsmax again, what's happening here? 

In fact, you are mixing up two things. First of all, hardware calibration of your monitoris a very good first step. When you are working with an LCD screen, calibration is even

more essential. If you don't have a calibrator yourself, consider to borrow one, or at

least use this guide to do basic calibration. When calibrating your monitor, set your

  whitepoint to 6500K (most monitors have an option to choose a whitepoint).

Calibrating your monitor is important to match your monitor gamma to a certain

standard. For Windows based systems, this standard gamma is 2.2. When you have

calibrated your monitor with a hardware calibrator, the accompanying software will

create an ICC profile. This profile helps to output the right colors on your screen, when

 your screen is offered an image from the web or other applications. In fact it transforms

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the colors to correct for the error in your monitor. Summarizing the story above, after

calibrating, you get closest to viewing content as it is meant to be.

Secondly, the virtual camera of your rendering application (in my case Vray but many 

others as well) has a linear response to light. In other words, its output has a gamma of 1.

If you are working in 3dsmax, the gamma correction is by default off. No gamma

correction means basically that you are using a gamma of 1. Thus, by taking no action,

3dsmax assumes that you will view your output on a device which has a linear response

 behavior and that all material you work with has also a linear gamma! Since you have

calibrated your monitor to work in a 2.2 gamma environment, the output of 3dsmax

 will look far too dark on your monitor. (as a side note, if you don't calibrate it will also

look too dark, because you CRT monitor has its own gamma, which is about 2.5*)

To illustrate this, look what a gradient and 50% gray in a linear gamma looks like on a

2.2 gamma monitor(left) and compare it with the linearly interpreted image (right). In

other words, when you display a linear image on a 2.2 gamma monitor without telling

that it is linear, it is interpreted as gamma corrected, and therefore displayed to dark.

In other words, changing gamma influences the midtones of your image. A gamma >1

makes the midtones darker, a gamma <1 makes the midtones lighter.

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Now you may think that you don't need gamma correction. That's probably because you

have been using all sorts of tricks for years to get the desired result. (Tricks like adding

linear falloff lights, or lights without decay, bright multipliers etc. etc.) All these tricks

 you have been using were to get a more realistic result, and without knowing, you were

actually trying to correct for your monitors gamma!

Great, so far I understand it. I read somewhere that CCD's in digital cameras alsohave a linear gamma, but I never needed to correct them when viewing them onscreen. Why is that then? 

This question actually supports the idea why you should use gamma correction. When

 you take a picture with your digital camera, light is captured with a CCD (well, in most

digital cameras it is). This CCD has in itself, a linear response curve, or in other words,

a linear gamma. This raw linear data is then mapped to a different gamma (2.2) and

colorspace, most likely sRGB or Adobe RGB. Professional image editing software that works with ICC profiles, can read the profile that is attached to your camera's picture,

and can interpret it right to display the correct tones and colors on your monitor (if it is

calibrated correctly!)

 So how about pictures on the internet then? 

 Although the majority of internet users will never have calibrated their monitor or

know anything about color management, cameras (and probably many internet

publishing software packages) will do some basic correction without telling the user. As

I mentioned earlier, a standard CRT monitor will probably be about gamma 2.5.

Therefore it is advisable if you publish pictures which need to look correct for the

majority of internet users, you convert your images for publishing to a gamma 2.5

profile (look for Native PC profile on that page).

 Right. So to summarize, it's just about setting the display gamma in 3dsmax to 2.2 inorder to display the linear rendering data correctly on my monitor? 

That's true, but there is a little more to take care of. If you have paid attention and

understand all concepts, you will know that there is a last step that has to be taken for

making correct renderings: You need to correct your materials and textures. You willneed to tell 3dsmax that the textures you use have already been gamma corrected. This

can be done either globally or locally. Globally it can be assigned in gamma tab:

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Don't worry about the dithered and solid gray squares, because they have nothing to do

 with accurate calibration.

Locally you can assign the bitmap a 2.2 gamma in the bitmap load dialog.  Please take

note of the fact that this rule only applies to textures that have been gamma corrected.

 In case you would make your own textures, it is of course better to keep them in linear 

space, and tell 3dsmax in the bitmap loader that it has a 1.0 gamma.

Finally let's look at the following figures. Figure 1 shows the old situation without

colormapping. As you can see, you are offering Vray gamma space textures and colors,

since you judge them based on what your monitor displays. In the end you are judging

the linear rendering again on what your monitor displays and try to correct for it (by 

using the tricks mentioned earlier)

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 You can convert these files to work in linear space by turning on gamma correction, as

shown in figure 2. Your materials (colors and texures) will look washed out. Therefore

 you correct the colors manually, or with the color correct plugin by Cuneyt Ozdas. The

only thing you need to do is copy the old color to the color correct map, and apply a

gamma correction of 2.2. Textures can be handled by turning on gamma correction for bitmaps as shown earlier.

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In the most ideal situation (figure 3) you keep all your data linear and only correct the

output to your display. The data is not touched, no gamma correction is burned in. Only in the very end, when publishing on internet for example, you will covert (a copy) to a

non-linear profile.

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O.K., enough theory I'd say. Can you show me some examples? 

Sure. The following images were rendered using the described linear workflow.

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 I think it is about time that I start experimenting myself. Can I email you withquestions regarding this technique? 

Of course. You can always ask me questions by filling in the form on the contact page.Or post your questions in this thread on the vray support forum

Monitor calibration

If you are serious about color, I strongly advise you to calibrate your monitor. It is

preferred to do it with hardware calibration (for example iOne from Gretag McBeth).

 You can abtain a reasonable result doing it manually - at least for CRT screens. If you

  work with LCD screens, manual callibration is hardly possible, because gamma is

changing with the viewing angle. Basically the steps are as following:

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First, make sure you have proper blackpoint setting and set your monitor to 6500K 

 whitepoint. (for film you might need a different whitepoint setting like 5600K). Second,

choose the appropriate gamma chart from AIM-dtp (although it principally sucks, I

suggest you take gamma 2.2 as a calibration reference, since many textures, photos and

stuff on internet as well as most pictures from consumer grade digital cameras are

sRGB. Besides, not all image editors like Photoshop use ICC profiles when displaying

images) Display the chart while adjusting the sliders in adobe gamma until the chart

shows no colors and the gray bars appear to have the same luminance.

• the main page of AIM- dtp

•  A guide for adjusting the blackpoint of your monitor.

• some gamma charts to evaluate your monitor

Sources:

Estuve viendo, y descubri algo

qeu podia ser interesante.

Estuve haciedno render con hdri

y vray y la imagen me quedo

realmente bien.

Ahora, tocando los parametros

del system, cambie el tamaño de

los cuadros qeu hace los render

(cuyo caso mio, al tener una dual

core, tengo 2 cuadors que hacenimagenes), el render pude ser

qeu lo aga en menos yiempo, y

mas realista que lo normal.

Solamente cambie la opcion en

system / render region divicion /

el menu qeu dise Region W/H a

Region Count.

Espero qeu estedes pruven y

digan sus opiniiones

Volver arriba  

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3DSanJuan

Gran Experto

Registrado: 31 Dic 2005

Mensajes: 2204

Ubicación: san juan, argentina

Publicado: Vie Feb 15, 2008 6:47 am  Asunto:

te dedico mi post 2400 para agradecerte el dato!!!

esos cuadraditos se llaman backets! y de esos backetspodremos obtener como vos decis, mayor tiempo de

render!

pero todo tiene que ver como siempre, cual sea nuestra

escena!

se supone que el antialiasing y otros parametros de vray

se calculan en la union de backet y backet.

si le agrandamos el tamaño a dicho cuadradito, pero en

una escena donde la mayoria de la geometria es simple y

pura, seguramente ganaremos mas tiempo para nuestro

render!

si es una escena complicada, llena de angulos y salientes

y volumentes que generan sombrs y cambian de colores;pues bien, el tamaño del backet tiene que ser de menor

tamaño para quedar bien.

pruebenlo y me dicen, si?

saludos!

 _________________

contra el mal... ...la hormiga atooomicaaa!!

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Knight fo the Light

Junior

Registrado: 18 Jun 2007

Mensajes: 104

Ubicación: Santa fe - Argentina

Publicado: Vie Feb 15, 2008 5:30 pm  Asunto:

Ademas sirve para pasar el tiempo, ya que los

cuadraditos chiquitos se mueven con mayor velocidad ya

que conentran los prodesos en un solo puntos y bueno,

no te aburrus como lo hacias con el otro grande que no

se mvodai nunca

Ahora estoy probando con los filtros, asta ahora e

probando que la mejor conbinacion de filtro es:

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Type: Adactive subdivicion

Antialiasing Filter: Catmull-Rom

Es lo mejor para calidad y efectos, la imagen es muy

nitida y hermosa. Espero que lo pruben y con los

cuadraditos chicos o backets como se diga

Otra cosita para un poquito mas detalles, cuado utilizan

un mapa Hdri, pongan el multiplicador del mapa en 2 y

no en 1 (en la pestaña donde dise Indirect Ilumination

GI).

Asi es mucho mas realista