Im sorry, but I need to learn the LWF method...

V-Ray for 3ds Max V-Ray for 3ds Max :: Issues
1

I apologise again for asking the same question as probably a 1000 other people, but I have read plenty of LWF topics and the way to set it up, but im still confused…only about a few settings..i kind of understand the principle behind it, but just to to be clear on a few specifics.

Can i just run through what I think I need to do to setup for LWF.

1. Calibrate monitor. ( I have an LCD monitor (LG Flatron L1915s) with 3 settings for gamma, - 50, 0 and 50. So im not sure which is the correct setting). The manual doesnt offer any gamma equivalents for these values.

2. Change max gamma to 2.2 and input gamma to 2.2. Tick both affect color and affect material editor.

3. Change the RGB multiplier in vraycolor to .255 (Im not sure why I need to do this, it seems my materials are really dark when I do this, but this may be to do with my vray cam settings).

4. At this point, when I render out, how do I know what vray camera settings to use and also, when I view the finished render, do I have to click on the “display colours in Srgb splace” ?

Does this LWF work for interiors and exteriors ?

Thanks for your help

2

1: this part is crucial. go here and follow the guide to figure out what gamma space your monitor is in before doing anything. To sum it up, first follow the preparations, and then go through the different calibration images in the left menu. There are two bars on the left in the images. When you squint or look at the image from a distance the two bars should appear to be identical. You need to find the image that is closest to that. So when you find an image that fits you have found you monitor’s current gamma space. If that gamma space is closer to 2.2 then you should calibrate it to that, and if it’s closer to 1.0 then you should calibrate it to that. most LCD monitors are around 1.0.
Now, if you don’t have any gamma controls on the monitor you’ll have to use software to do it. the nvidia control panel has built in display adjustments you can use. What you need to do is go to the gamma space picture you want to calibrate the monitor to on the website and change the gamma until the bars on that picture looks identical.
Once they do you have calibrated the monitor properly.

2: The gamma correction setting in max needs to be set to the same as you calibrated the monitor in. So either 2.2 or 1.0. The input gamma is different however. It needs to be set to the gamma of the pictures you most often use as textures. Usually 2.2, but if you make them yourself on a 1.0 gamma space monitor then they shouldn’t be gamma corrected on input. So if you mostly have pictures downloaded from the net or similar and most are 2.2 (which is the case most of the time) then you should set input gamma to that. but if you want to use a picture that is in gamma 1,0 then you have to change the multiplier in the texture setting for that picture individually.

3. The .255 thing is a bit different. It’s a mix between LWF and a workaround for a bug in previous versions (RC3) of Vray where the Vray Sky was too dark. In the new builds you should probably set it to .4545 (which is the mathematical inverse equivalent of 2.2) the reason for that is that the normal color swatches in Max doesn’t support floating point and generally refuse to behave.

4. The sRGB button is to show what the picture will look like after it’s gamma corrected back to 2.2 (which shouldn’t be done until all post processing is finished. And sometimes not even then)

5. Yes.

Note that I’m not entirely sure what the best practice is with LCD monitors in getting it to display things exactly how they’ll end up. someone want to fill in the blanks?

3

Ok, so i have calibrated my monitor to gamma 1.0

Set max gamma to 1.0, input gamma to 2.2.

I have set the color mapping in vray to linear and 2.2. (is this correct?)

I use leles exposimeter to set the camera exposure. (is this correct?)

I render out the scene to vray frame buffer without any curve correctection etc and the scene comes out really dark. Well, it looks like that on my monitor anyway. But my monitor is set to 1.0 gamma so it is really dark now anyway.

This image is saved straight from the VFB as a jpg.

This is before I have even changed the multipliers for the colors and textures to 0.454. If I did this, the render would be even darker, and I imagine, the light would be hard to bounce around the room.

4

Simplest LWF:

1) Calibrate monitor to 2.2 gamma (& 6500 K white point)

2) Change Max gamma to 2.2 and bitmap input gamma to 2.2. Tick both affect color and mat. editor.

3) In MFB, your rendering is correct. In VFB, check the sRGB button.

4) Save image as .EXR (which photoshop applies the sRGB to as default, though of course because it is floating point, it is not actually burnt in), and open in photoshop. It should look almost identical to your MFB. Or, save as JPEG (or other 8-bit format) and click Gamma, Override: 2.2.

That’s it. That’s all you need to do (at least in Max 8, Vray 1.5 RC2).

Notes:

Everything will appear too bright if you open an old file. Click the option “Load Enable State with Max files” if you want to switch back and forth between non-LWF and LWF files. Eventually all your recent work will be LWF and you won’t need this feature.

Keep in mind you will need to use less light in a scene, because your mid-values are now displayed at the correct brightness. Don’t overlight your scene or your contrast will look washed out (this is a common rookie LWF mistake). With less light, your renderings should be faster, whenever using GI.

For color mapping, I either use Linear defaults for interiors, or Reinhard with 0.5 burn, particularly for exteriors. The LWF brightens up the mid-values, and Reinhard burn will darken your overbright high-range values, which is often necessary with the Vray sun. You don’t want to change the gamma setting on the linear if using the method I outlined above.

The only workaround you will need is if you are trying to match a specific RGB value in your diffuse color slot in a vray material. In that case, use the Color Correct plugin.

I don’t understand why I would need to use the .255 thing. The above steps are all that’s needed for LWF.

LWF has nothing to do with interiors or exteriors. Its simply a way to make sure the mid-range values you see in your FB are the same as those used by your display.

Isn’t Lele’s exposimeter simply a method for making the VrayPhysicalCam behave like a dSLR camera’s multi-zone/matrix light metering mode? That has nothing to do with LWF.

Are you in London? I am going to give a tutorial on this as some point at one of the 3ds London meetings.

Have you read the two canonical essays on this subject?

http://www.highend3d.com/3dsmax/tutorials/rendering/vray/147.html

(the methods for establishing LWF in Vray are a bit dated in the link above, but it nonetheless explains LWF effectively)

http://www.gijsdezwart.nl/tutorials.php

5

@ Clifton

So you presumably find the 3ds London meetings usefull. Any idea when you may be presenting this?

Thanks

6

The last one wasn’t all that great (which was also my first one. I’ve heard the previous one (or two?) were good.), but I thought is was good for networking afterwards. Larry says he can’t work me into the schedule until February.

From our London Vray drinks we have established a group, and we have started doing informal “senior” tutorials, at which I have explained this to a couple people. We are now planning on doing these monthly at a host office. PM me if you are interested in this.

7

Right. LWF doesn’t have anything to do with exposure.

The physical camera is intended to work as a normal camera (with shutter, aperture, iso and so on) and changing those settings is the correct way to change the exposure. if you don’t use the physical camera you need to change the multiplier of the lights instead.

LCD monitors can be really annoying when it comes to gamma. Especially laptop ones. I still haven’t been able to calibrate mine.
If you calibrated it to 1.0 then normal images you see on the web should appear way too bright. And in fact, when I checked, the picture you uploaded looks okay in 1.0 linear gamma space.

Oh and if you set the input gamma to 2.2 you should NOT set the texture multipliers to .4545. that’s what the input gamma is for. You should however to do with the vraycolor map as it’s not affected by it.

compare this picture to the one you posted:

which one looks the most correct?

8

Just to clarify, I don’t believe your .4545 suggestion makes sense. It’s just that a RGB .4545 value has no real relationship to the gamma 2.2 value. Yes, .4545 is the mathematical inverse of 2.2, but a gamma correction is by definition non-linear and setting the RGB multiplier simply multiplies the color values, which is linear. With apologies to him, Lele’s .255 method worked by attempting to simulate the true albedo(?) of a surface when using the vray sun and sky with the physical camera. At the same time it was having to deal with a slightly flawed sun/sky system that has been corrected in 1.5. In my experience with 1.5, I’ve gotten pretty good results leaving the multipliers alone but your experience may vary.

9

Ok, thanks for the tips, ill run through them and see what I come up with.

Clifton - I live in Worthing, but I could travel up…would be a worthwhile visit no doubt ! I really need to nail this workflow down so I can produce quicker and more consistent imagery.

Shimakaze - I guess the altered picture you show me looks better…it looked similar to mine on VFB with sRGB switch on, but the colours look washed out.

So after reading Cliftons post, he says I need less light…but that would mean changing the standard vray sun levels, which surely can just be left at standard.

So now im confused about what I need to do to get my colours back to looking more natural and not washed out. Do i apply changes to the multiplier or do I use color correct and apply a gamma correction there ?

Do I also have to change the reflection amounts as they seem too high with the altered image shown above ?

10

The reason your image looks like Shimakaze’s in the VFB with sRGB turned on, but not it the saved image, is because you are not doing step 4 as I outlined above.

For looking washed out, use less light, and make your materials darker. What appears as mid-grey in a mat. editor slot slot with gamma enabled, is actually quite a dark grey in terms of RGB. All your old materials that are not bitmap based, were created with incorrect non-LWF values in mind, so they are too bright.

If you are using VRayPhysicalCam, you should leave the sun at 1.0. Adjust your ISO, shutter speed, and f-stop accordingly.

To start, with my method at least, leave color mapping alone. Do not use any multipliers or color correction. Do not adjust any of your bitmaps. They are corrected when you set you bitmap input gamma at 2.2. Get the scene looking as good as possible with just exposure and materials. Then apply either Reinhard burn or Exponential to take down the hotspots you might have.

You might have some sampling noise in low-light situations. Just increase your Hsph. subdivs if necessary.

Like anything else, just keep practicing. It took me a few days to get my images looking good after switching to LWF.

11

Check out this image I did a few months ago. LWF of course. Plenty of dark areas and contrast.

I must credit Osmosis for their wonderful study hall model (as well as their fantastic classic Vray 1.09 tutorials). I remodeled about 98% of it, and re-did all the materials for high-res equirectangular panorama tests. Original image is 8000x4000.

12

Im so glad you posted this type of image, because I was trying to work out how the hell to get that 360 degree type of result. ANy tips on how to do this ?

Very nice image by the way. To me it looks very dark inside and correct outside. I guess this is physically correct to what a digital slr would do if the exposure was set for the outside.

Im just rendering out the office image again. I did some smaller tests and I think it is looking fine now. Had to bring Rhinehard burn down to 0.4 for the highs not to be burnt.

Just to confirm though, with these settings…the gamma will not be burnt into the image, and can be adjusted in photoshop after saving out to the exr format ?

So if i want to burn the gamma into the image i simply turn the color mapping gamma to 2.2 ?

I’ll post the updated version of the office once its finished…nearly there :slight_smile:

One more thing…if i save to a vrimage (basically because of memory issues) and view the image using max, is that the same as viewing it in the Vray frame buffer..so if i save out to the exr format it will be fine still ?

13

To get this type of panorama, you need to use a max standard camera with Vray Spherical camera and FOV of 360.

If you save as EXR, in photoshop it will open with the sRGB profile applied, and will look like your frame buffer. Because its full float, you could “undo” the gamma if you wanted (and redo it later, etc.)

If I want to burn in the gamma, just save as JPG with gamma override of 2.2. No need to burn it in in advance with color mapping.

The only benefit I’m aware of using the gamma 2.2 in color mapping is it allows for the GI sampling to understand the correct brightness of the space, so you won’t get sampling noise in low-light spaces (or so I’ve heard… haven’t experimented yet).

14

Ok, thanks everyone for the tips. Finally, i think this has worked well. Heres the image (so far). Got plenty more stuff to do.

Cheers Clifton

15

I guess what’s confusing you is that the input gamma in the max settings isn’t really a multiplier but a divider. Meaning if you want to get the same result in a texture without setting it globally you have to use .4545 multiplier (and you have to use it regardless in Vraycolor maps). You’re right about the .255 thing though. But you still have to take it into account even though the sky has been fixed. But this is more up Lele’s alley.

Steveiouk:
Glad you got it working! :smile:

16

I don’t believe I’m confused about this. The input gamma is just what it says it is - a gamma adjustment, it’s neither multiplication or division, but applies a gamma curve to the incoming image. Setting the multiplier values in the material simply multiplies all of the image values by a given number (in your case .4545).

If you follow Lele’s tutorial, you set the diffuse color to black and set the difuse spinner to 25.5 which effectively multiplies all of the diffuse map values by .255. With this method a gradient ramp that went from 0 to 1 would now go to 0 to .255. In contrast a gamma curve would keep the min/max values of the ramp at 0 and 1 but would adjust the mid grey point depending on the gamma value. A gamma curve is not the same thing as a value multiplier.

17

Aaah I see what you’re talking about now. Problem is you don’t have any choice unless you know how to specify the exact gamma curve since there is no actual gamma control. So changing the output multiplier is the closest you get.
In 1.5 there is gamma correction built into the Vraycolor map though which would remove the need for the .4545 thing altogether. Haven’t had time to do any tests yet though.
Just curious, how would you go by doing it? If you needed to use two textures, one which was in sRGB space and one that was in linear space (without gamma correcting in a different program first)?

18

Using straight Max, you could probably get a decent approximation by using the color map options under the output setting for the bitmap (either by plotting input and output points that correspond to a 2.2/.4545 gamma or guestimating a bezier handle on the first point). Otherwise you’re best bet is to probably use some plug-in like the ColorCorrect map which has a spinner for a gamma value.

19

Problem is there is MANY different ways to effectively use/implement LWF.

Just a matter of finding one that suits you and work your workflow and sticking to it.

In the end .. it doesnt really matter what you do as long as the final product looks good :smile:

20

Well said :wink: