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View Full Version : Video: Gamma / Tonemapping Options in Kray



Matt
11-04-2009, 09:21 PM
Here's a quick video to show the gamma correction, linear workflow and tonemapping options in Kray.

QT H.264, 18MB Zipped
Video: Gamma Correction, Linear Workflow & Tonemapping Options in Kray (http://www.pixsim.co.uk/video_tutorials/Gamma_Correction_Options_in_Kray.zip)

This is not so much a video tutorial, but more a quick look at the options.

Hope someone finds it useful!

Cheers
Matt

jay3d
11-05-2009, 04:26 AM
Thanks Matt!, appreciated! :thumbsup:

geo_n
11-05-2009, 04:27 AM
downloading :D. thanks matt

geo_n
11-07-2009, 08:00 PM
I didn't know it was pronounced as krey as in gray and not kayray as in cake.:D

Intuition
11-07-2009, 08:23 PM
Actually helping a fellow Lightwave artist learn Kray last week. We had to resurrect an old car commercial that was done in LW.

Since its staying in LW I had him fire up Kray. Its turning out really nice.

Great work on the interface Matt. :D

Matt
11-07-2009, 08:35 PM
I didn't know it was pronounced as krey as in gray and not kayray as in cake.:D

Actually, I'm not sure if it's Kray or K-Ray!

Larry_g1s
11-07-2009, 10:03 PM
Thanks Matt! I think it's Kray. That's how I say it at least. lol

jwiede
11-08-2009, 11:08 PM
I've always thought of it as "Kray" (same pronounciation as the computers), because the site refers to "KrayTracing". "K-Ray-Tracing" doesn't sound as smooth as "Kray-Tracing" to me. Go figure. Either way, I've been a happy customer of theirs for some time.

jwiede
11-08-2009, 11:36 PM
Matt, I wanted to confirm something from the video: The QuickLWF plugin acts to just remove any gamma correction programmed into the render itself from the "sources" selected in the plugin (backdrop, textures, lights), correct? Put another way, it omits gamma correction from their contributions to the samples (because otherwise they'd wind up being doubly-corrected)?

What I didn't quite understand what how the QuickLWF plugin interacts with the Tonemap Blend plugin when both are active. What settings should go in the QuickLWF plugin when you have multiple corrections active in the Tonemap Blend plugin? Ideally, you'd want to program QuickLWF with whatever computed gamma correction value results from the correction blend, wouldn't you?

I don't see an easy way to achieve that, though, it seems like we'd really need the QuickLWF to pull the output value from the Tonemap Blend plugin automatically somehow. Are the Kray guys planning to add that (or is it already there)? Or am I misunderstanding how the two interact?

Thanks for the video, very helpful! I didn't quite understand the intent of the new plugins when I downloaded the latest "beta", but your video cleared up most of my questions.

Matt
11-09-2009, 02:35 AM
Matt, I wanted to confirm something from the video: The QuickLWF plugin acts to just remove any gamma correction programmed into the render itself from the "sources" selected in the plugin (backdrop, textures, lights), correct? Put another way, it omits gamma correction from their contributions to the samples (because otherwise they'd wind up being doubly-corrected)?

Yes, QuickLWF only removes the specified gamma from the sources you check in the panel.


What I didn't quite understand what how the QuickLWF plugin interacts with the Tonemap Blend plugin when both are active. What settings should go in the QuickLWF plugin when you have multiple corrections active in the Tonemap Blend plugin?

The sources (images / colours) etc. only need the gamma they have 'added in' removed, to bring your workflow to all linear for the renderer. No matter what settings you use in the Tonemap Blending plugin, your sources still had gamma added in (usually 2.2) this is all you want to remove.


Ideally, you'd want to program QuickLWF with whatever computed gamma correction value results from the correction blend, wouldn't you?

The important thing to remember about Linear Workflow is that all of your images, colours etc. are in linear space before being fed to the renderer (which works in a linear space). Hence the name Linear Workflow.

You are ensuring everything is linear.

Once the sources have gamma removed, you are free to tonemap as you want using the Tonemap Blending plugin. Whether you just add gamma back in or tonemap is entirely up to what you think makes your render look best, this is the subjective part.

geo_n
11-15-2009, 07:20 PM
In the video the pixel order was frost which I agree looks cool. Anyone notice that kray doesn't use all cpu when using other pixel order other than scanline? Must be a bug since my cpu sometimes goes down to 60%.

toby
11-15-2009, 08:53 PM
Matt, what you're missing from the linear workflow is adding the gamma back on after the render, for viewing purposes. Non-linear is the way our eyes percieve light, that's why gamma is in all the images on the web, so if you don't add the gamma back on at the end it won't look right. It's after you view it with the gamma curve that you judge whether to increase the gamma to brighten a room, usually in a compositing app. Just be sure to save floating point images!

Matt
11-16-2009, 03:53 AM
Matt, what you're missing from the linear workflow is adding the gamma back on after the render, for viewing purposes. Non-linear is the way our eyes percieve light, that's why gamma is in all the images on the web, so if you don't add the gamma back on at the end it won't look right. It's after you view it with the gamma curve that you judge whether to increase the gamma to brighten a room, usually in a compositing app. Just be sure to save floating point images!

Erm, no I'm not! :)

It's added back in during the tonemapping part.

toby
11-16-2009, 01:41 PM
But a linear workflow doesn't require tonemapping; it does require a gamma curve before judging how the render looks; in other words, before you tonemap it. Linear colorspace is *only* for accurate math inside the render.

Matt
11-16-2009, 03:13 PM
Tonemapping is just another way of applying gamma, if you watch the video again, you'll see that I add a mix of Gamma 2.2 and Exponential.