Linear workflow, Vray, and Maya

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  01 January 2011
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.
 
  01 January 2011
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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http://www.djx.com.au
 
  01 January 2011
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
 
  01 January 2011
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.
 
  01 January 2011
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
 
  01 January 2011
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
 
  01 January 2011
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.
 
  01 January 2011
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?
 
  01 January 2011
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
 
  01 January 2011
thanks for the heads up.
 
  01 January 2011
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
 
  04 April 2013
I know this is old thread, but something interesting from CHaos forums recently:

This is posted by a Chaos Group developer talking about "linear workflow" checkbox:

Quote: One questions is always asked when I talk about this setup - Why in the help file is written that this workflow is not correct - it is just because there is a tiny difference between Gamma and sRGB curve. Vray Gamma Setup and the 3DSMax Gamma setup are not 100% correct LWF just because Gamma curve is different that sRGB curve - the difference is very very small. At the end Vray and 3DSMax LWF setups will produce the same result - but with Vray setup it would be easier to work with!


I guess the same would translate to Maya and manually gamma correcting.

The only thing to remember is that the linear workflow checkbox will not apply gamma correction to environment slots, as a texture for the lights and V-Ray light material and some other things like car paint material. Its pretty obvious when it happens anyways.

So there we have it.

Last edited by Hamburger : 04 April 2013 at 05:22 AM.
 
  04 April 2013
Hey thanks for posting that.

Recently I read that we need to gamma correct our light's slots as well, now i saw a video in i believe cinema4D, where your light slot is also gamma corrected.
How important is that in VRay in Maya?
Any idea anyone?
 
  04 April 2013
Yes, if you use Linear Workflow checkbox, I believe you still have to gamma correct a texture if you are plugging it into a light. From what I gather from CHaos said anyway.
 
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