Linear workflow, Vray, and Maya

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Old 01 January 2011   #1
Linear workflow, Vray, and Maya

Righty-ho chaps, some advice if you'd be so kind

I see in the Vray manual (http://www.spot3d.com/vray/help/may...olormapping.htm) it is stated that the 'linear workflow' checkbox in vray's Color Mapping tab is apparently NOT intended as a replacement for "proper linear workflow", which I take to mean applying a gamma curve node of .454 to all your textures?

I had just been checking 'Linear workflow' in the Color Mapping tab, and then setting the Gamma in the same tab to 2.2 and firing away (note this is for saving images straight from the VFB render window)

Should I instead be doing things the old-fashioned way? And where does 'Affect swatches' fit into all this? Is it a replacement for adding .454 nodes to each texture?

Last edited by Richard7666 : 01 January 2011 at 03:18 AM.
 
Old 01 January 2011   #2
I regard the line you are referring to as a kind of disclaimer.I would reword it as "checking this box will not solve all your linear workflow issues". However it solves most of the common ones though. I think you'll find people that leave it checked and others who don't. I'm one of the ones who leave the box unchecked.

So my color mapping settings are:
linear multiply, gamma 2.2, affect background ON, subpixel mapping ON, Dont affect colors ON, linear workflow OFF, clamp output OFF, affect swatches ON.
Render to exr 16-bit (half float).
Use the sRGB lut in the VFB
Check "convert image to sRGB for RenderView", and copy images to RenderView for saving in 8-bit formats.

You dont need the old gamma correct node for fileTextures because you can add the vray "bitmap input gamma" attributes to the fileTexture node. The defaults are correct for linear workflow on a sRGB monitor.

"Affect Swatches" changes the display of the swatch in the attribute editor for vray materials so that they show the effect of your color mapping choices.

David
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Old 01 January 2011   #3
Hey, David,

I am curious why you opt for subpixel mapping ON and linear workflow OFF?

Regarding the subpixel mapping, there are some discussions on the Chaos forum, but I haven't investigated it enough. Just did a test last night. Rendering with subpixel mapping ON, it will cut the render time quite a lot for the test scene. Though I found that the specular reflections are much dimmer. This might affect post glare IMHO.

Regarding the linear workflow OFF (using Vray bitmap input gamma instead), is it for finer or localized control?

cheers,
Jason
 
Old 01 January 2011   #4
Originally Posted by jasonhuang1115: Hey, David,

I am curious why you opt for subpixel mapping ON and linear workflow OFF?

Regarding the subpixel mapping, there are some discussions on the Chaos forum, but I haven't investigated it enough. Just did a test last night. Rendering with subpixel mapping ON, it will cut the render time quite a lot for the test scene. Though I found that the specular reflections are much dimmer. This might affect post glare IMHO.

Regarding the linear workflow OFF (using Vray bitmap input gamma instead), is it for finer or localized control?

cheers,
Jason



I'm actually curious as well...Thank you for the Vray bitmap tip, I couldn't figure out why my images still looked washed out yet I had checked the linear workflow checkbox before I set up my scene. So far Vray has been a pleasure to work with, the render elements are a real treat.
 
Old 01 January 2011   #5
Originally Posted by djx: I regard the line you are referring to as a kind of disclaimer.I would reword it as "checking this box will not solve all your linear workflow issues". However it solves most of the common ones though. I think you'll find people that leave it checked and others who don't. I'm one of the ones who leave the box unchecked.

So my color mapping settings are:
linear multiply, gamma 2.2, affect background ON, subpixel mapping ON, Dont affect colors ON, linear workflow OFF, clamp output OFF, affect swatches ON.
Render to exr 16-bit (half float).
Use the sRGB lut in the VFB
Check "convert image to sRGB for RenderView", and copy images to RenderView for saving in 8-bit formats.

You dont need the old gamma correct node for fileTextures because you can add the vray "bitmap input gamma" attributes to the fileTexture node. The defaults are correct for linear workflow on a sRGB monitor.

"Affect Swatches" changes the display of the swatch in the attribute editor for vray materials so that they show the effect of your color mapping choices.

David


the defaults are 2.2 , this is correct? dont you want to degama it to .455
 
Old 01 January 2011   #6
Originally Posted by neuk: the defaults are 2.2 , this is correct?
Yes. It simply means "this image is sRGB". It save you having to do the math and figure out how to degamma it.

Originally Posted by jasonhuang1115: I am curious why you opt for subpixel mapping ON and linear workflow OFF?


subpixel mapping ON to avoid aliassing artifacts, especially on thin overbright highlights and edges. This might also explain why your reflections looked a bit dimmer.

linear workflow OFF so that I can decide what needs correction and what does not (as you suspected). I think that vray actually does a good job of guessing when you have this ON (especially if you use vray materials), but since I have a good understanding of linear workflow, I think it is safer to control this manually and leave it OFF- which is easier in vray than mray I think.

David
__________________
http://www.djx.com.au
 
Old 01 January 2011   #7
Originally Posted by djx: subpixel mapping ON to avoid aliassing artifacts, especially on thin overbright highlights and edges. This might also explain why your reflections looked a bit dimmer.

linear workflow OFF so that I can decide what needs correction and what does not (as you suspected). I think that vray actually does a good job of guessing when you have this ON (especially if you use vray materials), but since I have a good understanding of linear workflow, I think it is safer to control this manually and leave it OFF- which is easier in vray than mray I think.

David

Thanks for the explanation, David. I'll dig deeper to learn further the impact of subpixel mapping.
BTW, great new post on your blog. Looking forward to seeing more Vray and Nuke stuff coming.
 
Old 01 January 2011   #8
Originally Posted by djx: I regard the line you are referring to as a kind of disclaimer.I would reword it as "checking this box will not solve all your linear workflow issues". However it solves most of the common ones though. I think you'll find people that leave it checked and others who don't. I'm one of the ones who leave the box unchecked.

So my color mapping settings are:
linear multiply, gamma 2.2, affect background ON, subpixel mapping ON, Dont affect colors ON, linear workflow OFF, clamp output OFF, affect swatches ON.
Render to exr 16-bit (half float).
Use the sRGB lut in the VFB
Check "convert image to sRGB for RenderView", and copy images to RenderView for saving in 8-bit formats.

You dont need the old gamma correct node for fileTextures because you can add the vray "bitmap input gamma" attributes to the fileTexture node. The defaults are correct for linear workflow on a sRGB monitor.

David



Thanks a lot David, only one question; what exactly is the vray "bitmap input gamma" attribute and how should it be used? In conjunction with the settings you described in the prior paragraph?
 
Old 01 January 2011   #9
Originally Posted by Richard7666: what exactly is the vray "bitmap input gamma" attribute and how should it be used?


Select any node in maya and open the attribute editor and depending on what node it is you can add extra vray attributes (using the drop-down attributes|vray menu). If you select the fileTexture node you'll be able to add a pair of attributes by selecting "bitmap input gamma". The first is just a check box to enable/disable the gamma correction, the other lets you specify the gamma value of the image. The default value is 2.2 since almost all 8-bit images are in sRGB space. If "Enable input bitmap gamma" is checked (default) then the image will be gamma corrected to be in linear space. (So in the default case a gamma of 0.455 will be applied for you - and it saves you doing the math to figure that out).

If you had set Linear Workflow ON in render settings, then you would not need to add the fileTexture attributes. Some people prefer to work that way. I just like the extra control I get by doing it on a per file basis.

David
__________________
http://www.djx.com.au
 
Old 01 January 2011   #10
thanks for the heads up.
 
Old 01 January 2011   #11
I haven't had a problem so far with those settings but I would like to have the option of controlling it myself like I did previously in MR. I can't seem to access that attribute in the filetexture node David hmm, under vray there aren't any attributes for me to add?

Just to be confident with these settings in vray I did a quick test:
Vray for Maya gamma test
 
Old 01 January 2011   #12

You should have a menu in the attribute editor like this one. (this snapshot is from 1.5 sp1)

David
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http://www.djx.com.au

Last edited by djx : 01 January 2011 at 12:14 PM.
 
Old 04 April 2011   #13
I was wondering if you would use the gamma correction on spec maps, bump maps etc for Vray for Maya.

Also when using the Vray gamma correction attribute should you use SRGB or Gamma under the Extra Vray Attributes tab?

Thanks.
 
Old 04 April 2011   #14
I was wondering if you would use the gamma correction on spec maps, bump maps etc for Vray for Maya.


No. You only ever want to gamma correct Color values, not float/vector.
 
Old 04 April 2011   #15
Originally Posted by kpamir: when using the Vray gamma correction attribute should you use SRGB or Gamma under the Extra Vray Attributes tab?

The default gamma=2.2, which is close enough to sRGB that you probably wont notice any difference. From this point of view sRGB is probably the logical choice (although this is a more recently added option, so some people will not be seeing it). On the other hand you would use gamma if your image is not sRGB, but some other colorspace. This is less common of you are using simple 8-bit formats, but may be useful depending on where you images came from.

If you are not sure, its a good bet to go with gamma=2.2 or sRGB.

David
__________________
http://www.djx.com.au
 
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