linear workflow in houdini quick question...

[dyei nightmare]

i just wanna know in houdini where do you raise up the gamma to 2.2 and how can you reduce gamma to .455 in images... or in other words...

how do you set up linear workflow in houdini? ive seen some topics on this, but they are more about gamma correction itself..

i already know whats the linear workflow, i just wanna know how do you set up it in houdini??

[symek]

i just wanna know in houdini where do you raise up the gamma to 2.2 and how can you reduce gamma to .455 in images... or in other words...

how do you set up linear workflow in houdini? ive seen some topics on this, but they are more about gamma correction itself..

i already know whats the linear workflow, i just wanna know how do you set up it in houdini??

Linear workflow you say? It's a buzz word for something, which is simply the only correct way of doing things in CG, and as such was in use years before someone ingenious has named it "Linear Workflow". Basically:

1) Make sure all your work in done in a single color space.

2) Let it be linear space, because with tiny exceptions all color algebra assumes values are in linear space.

3) The main input of non-linear colors into your workflow are textures, thus make sure that:

4) Either your textures are linear, or you linearize them in shaders by multiplying with 1/2.2.

5) Finally make sure, that whenever you watch colors in Houdini, they have correct de-linearisation applied. Whether it's a viewport, render preview, mplay, color-picker, texture preview, composite, you should always watch it in sRGB space. Houdini applies LUT or gamma correction (as an option to LUT) to any of them, so once you set it correctly, you may forget about it.

6) Finally, saving your renders/composition to target formats (jpgs, movs, avi, etc) implies prior de-linearisation (*gamma2.2 for example).

[dyei nightmare]

Linear workflow you say? It's a buzz word for something, which is simply the only correct way of doing things in CG, and as such was in use years before someone ingenious has named it "Linear Workflow". Basically:

1) Make sure all your work in done in a single color space.

2) Let it be linear space, because with tiny exceptions all color algebra assumes values are in linear space.

3) The main input of non-linear colors into your workflow are textures, thus make sure that:

4) Either your textures are linear, or you linearize them in shaders by multiplying with 1/2.2.

5) Finally make sure, that whenever you watch colors in Houdini, they have correct de-linearisation applied. Whether it's a viewport, render preview, mplay, color-picker, texture preview, composite, you should always watch it in sRGB space. Houdini applies LUT or gamma correction (as an option to LUT) to any of them, so once you set it correctly, you may forget about it.

6) Finally, saving your renders/composition to target formats (jpgs, movs, avi, etc) implies prior de-linearisation (*gamma2.2 for example).

thank you a lot symek, though, my question is more about what parameters in a rop, or mantra node, or vex nodes are involved in this process, which settings do i need turn on?

is just about exporting the diffuse/color pass with 2.2 gamma as image plane?

what do i need change besides turning color space to gamma 2.2 in shading in the mantra node?

are there any shading nodes involved on gamma correction?

where can i change the gamma to 2.2 for batch rendering?

[symek]

thank you a lot symek, though, my question is more about what parameters in a rop, or mantra node, or vex nodes are involved in this process, which settings do i need turn on?

Ok, sorry for being general.

is just about exporting the diffuse/color pass with 2.2 gamma as image plane?

Nope, you render everything in linear space, just as it is by default, because rendering is hardly ever the end of the workflow.

what do i need change besides turning color space to gamma 2.2 in shading in the mantra node?

As above, don't adjust gamma on MantraROP. Adjust gamma (2.2, or apply 2sRGB lut) on Render View, mplay, Composite View, whatever you use. Go to Edit->Color Settings->Color Corrections and apply either LUT or Gamma to most of the places listed there.

are there any shading nodes involved on gamma correction?

where can i change the gamma to 2.2 for batch rendering?

ColorCorrectionVOP can apply 1/2.2 gamma for your sRGB textures.

[dyei nightmare]

Ok, sorry for being general.

Nope, you render everything in linear space, just as it is by default, because rendering is hardly ever the end of the workflow.

As above, don't adjust gamma on MantraROP. Adjust gamma (2.2, or apply 2sRGB lut) on Render View, mplay, Composite View, whatever you use. Go to Edit->Color Settings->Color Corrections and apply either LUT or Gamma to most of the places listed there.

ColorCorrectionVOP can apply 1/2.2 gamma for your sRGB textures.

AHH!! THANKS A LOT SYMEK!

Edited March 16, 2012 by dyei nightmare

[Netvudu]

We can only hope SESI will hear our suggestions at the beta forum and implement a more automatic way of doing this. It´s totally doable, but it´s a bit slow to linearize all textures manually.

I seem to recall the "nuke way" of doing things was agreed as the best way to implement it for Houdini.

[jason_slab]

what do i need change besides turning color space to gamma 2.2 in shading in the mantra node?

just a note on this, if you referring to the gamma 2.2 on the shading tab, u should set this to gamma 2.2 if your rendering PBR, it samples better in the dark areas.

I must say, one thing i am disappointed in with the release of H12 is the lack of improvements in Linear workflow, it might have been a bit of a "buzz" word, but adding the correct tools to make artists life easier is quite important, especially when coming from other apps, Houdini is behind in this area and can be confusing to the "artist".

j

[lukeiamyourfather]

4) Either your textures are linear, or you linearize them in shaders by multiplying with 1/2.2.

Sort of, a proper conversion is a little more complex than that.

http://en.wikipedia.org/wiki/Srgb#The_reverse_transformation

I use an inline VEX node for this in my shaders. I'll post it when I get home if anyone would like it.

[symek]

Sort of, a proper conversion is a little more complex than that.

http://en.wikipedia.org/wiki/Srgb#The_reverse_transformation

I use an inline VEX node for this in my shaders. I'll post it when I get home if anyone would like it.

Hmm, how about this:

and this: http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=23700&start=0&postdays=0&postorder=asc&highlight=

which really doesn't matter, as gamma correction, even if it's simplified, is close enough, so that most people I know use it. I had a LUT sRGB3Lin from Nuke, with which I have converted textures to rat, since I don't like to have sRGB textures at all, but then it appeared to me, and to most artists I work with, that it actually makes no difference.

[Fabiano Berlim]

sRGB_LUT.zip

This is a sRGB LookUpTable generated from Nuke.

Hope it helps.