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View Full Version : Rendering to nonlinear colourspace in 9.2?



Captain Obvious
05-04-2007, 10:00 AM
Is it possible, without the use of image filters? Because I would like to have it work in FPrime. Is it possible to do a gamut control in the Nodal system?

Exception
05-04-2007, 01:12 PM
Hmm, I don't know about that, but what's wrong with rendering to HDR and then using ToneMapping or VD to control your color space in a post-pass?

You'd like to preview it all at once?
Would be nice...

Weepul
05-04-2007, 03:23 PM
You could put a "transparent" plane in front of the camera, and use nodes to affect the output of a Transparency Shader node. To explain in more depth, you'd need to let us know what effect you want on the image.

It's a workaround, certainly. Generally, I'd instead suggest render to HDR like Exception said, and then load the image sequence back into LW in order to apply the image filters after the fact - or, of course, use another app.

Captain Obvious
05-05-2007, 06:26 AM
You'd like to preview it all at once?
Would be nice...
That is indeed the reason. Generally, you have to do gamma compensation in post. It would be very nice to be able to preview it in FPrime.




You could put a "transparent" plane in front of the camera, and use nodes to affect the output of a Transparency Shader node. To explain in more depth, you'd need to let us know what effect you want on the image.

How would that work, exactly? I haven't seen a way to control the actual shader output in Lightwave; only the value of the various channels. If you have an image map, it's a piece of cake to apply a curve adjustment to it in Nodal, but I haven't seen a way to do a curve adjustment on the amount of diffuse light it sends out.

Red_Oddity
05-05-2007, 06:37 AM
You could use a program like Gapa, it allows you to quickly switch from Gamma 1.0 to 2.2 with a user defined shortkey.
It is a workaround, but i have worked like this for a year with LW, and it works okay for previewing.

links help : http://www.donationcoders.com/stars/index.php?show=gapa

jameswillmott
05-05-2007, 03:51 PM
That is indeed the reason. Generally, you have to do gamma compensation in post. It would be very nice to be able to preview it in FPrime.

How would that work, exactly? I haven't seen a way to control the actual shader output in Lightwave; only the value of the various channels. If you have an image map, it's a piece of cake to apply a curve adjustment to it in Nodal, but I haven't seen a way to do a curve adjustment on the amount of diffuse light it sends out.

You can apply a curve adjustment in nodal to an image, you can also apply it to the output of a transparency shader in just the same way. I think. I haven't tried it but Weepul's concept is sound.

Red_Oddity
05-05-2007, 04:27 PM
Here's a node network that does what you want

Create a plane, place it in front of your render camera (and parent it so it moves along), assign the attached node network (connect to the color input of your plane's material) and you should have a realtime Gamma correction feedback.

Change the value of the Divide node called 'One / Gamma' to the gamma value you desire (value right now is 2.2)

Red_Oddity
05-05-2007, 04:55 PM
And while we're at it, here's a nice (complex and slow) node network to convert an image node from sRGB colorspace to Linear color space so you can really render things correctly.

The math is very simple, and maybe we could ask dpont or Michael Wolf to create a nice node that does color space / gamut conversions.

Lightwolf
05-05-2007, 05:25 PM
The math is very simple, and maybe we could ask dpont or Michael Wolf to create a nice node that does color space / gamut conversions.
Yes, I have been following the thread ;) And actually, I've thought about this for some time... however, that would imho only make sense with a gamma correcting image viewer (as well as gamma corrected openGL - something I've yet to see in an app).

I dig the transparent plane trick for FPrime! :beerchug:

Cheers,
Mike

Red_Oddity
05-07-2007, 08:58 AM
I forgot to mention, the plane with the Gamma node network connected should have set Diffuse to 0 and Luminosity to 100.

jameswillmott
05-07-2007, 09:08 AM
If you attached the output into the Diffuse Shading input, it is basically the same as setting diffuse to 0 and luminosity to 100%

monovich
05-07-2007, 02:46 PM
And while we're at it, here's a nice (complex and slow) node network to convert an image node from sRGB colorspace to Linear color space so you can really render things correctly.

The math is very simple, and maybe we could ask dpont or Michael Wolf to create a nice node that does color space / gamut conversions.

it's slow? I'm curious why. Isn't the sRGB to Linear conversion pretty straightforward math? I tried to do this /w nodes once, but wasn't able to. Always wanted a node to do convert image maps or even spot colors to linear for proper rendering.