By arthur argote (Archiea) (66.32.146.30) on Thursday, October 03, 2002 - 01:15 am:

Hey folks,

I posted this in the LW community forum. I figured i'd post this here, too, as its relevant..

I made a bit of headway in my dilema on getting combustion to work with Lw's extended color depth output.

As advertised, LW only float output was Tiffluvlog, flx and rad. These formats seemed proprietary as combustion didn't even see them, let alone load them. No surprise there.

However, I knew that Cineons also outputted float info albiet in a lut curve. Combustion loaded these fine, but my data was always clipped. Combustion allows you to set the bit depth and lut curve right in the footage node. Despite the viewer identifying the data in the cineon as float and 40 bit, I'd get clipped data.

In a bout of counter intuition that comes from desparation I decided to try something illogical. I left the settings in the footage as float but without a Lut applied. I then added a bit converted that supposedly converted a float image to float (????) and there, I delogged it in a LUT settings that the bit converted had (seemed odd place to have it). bingo. the speculars on my render went to 1.2 as opposed to being clipped at 1.0.

It seems odd that combustion would offer a bit converter and LUT adjustment that doesn't work as expected, yet keeping the image in Log and converted it later in a dedicated node worked. I understand the function of the bit converter, as i have worked that way in shake, but the redundant, yet nonfunctional options in the footage node I don't understand.

Whats important now, I guess, is that it works. I might want to remind folks here that discreet is offer combustion 2.0 with cleaner for $1,500. Originally, that would be like $5,500. For mac users this is more relevant, as the next package that offers this expanded color depth is the $5000 shake, not counting the $1200 yearly maintainance. Digital fusion on the Pc is offering it in 4.0.

By Julian Johnson (Julianjohnson) (62.49.23.72) on Thursday, October 03, 2002 - 02:27 am:

Hi Arthur,

This sounds really useful. I'm just experimenting with Combustion 2 now. Can you describe the counter intuitive bit in a bit more detail? :-) I've exported a 30bit Cineon seqence. I've left the footage node untouched (i.e. no LUT) and I've added a bit depth converter operator to the footage and changed that to float but my speculars are still being clipped.I'm not sure what you mean by delogging it in a LUT settings. I'm missing something simple here but Combustion is a such a different beastie to After Effects..

Julian.
The Mac Lightwave Resource Page
http://www.exch.demon.co.uk

By arthur argote (Archiea) (66.32.146.30) on Thursday, October 03, 2002 - 03:21 am:

My pleasure, julian...

Are you getting as far as understanding the settings in the footage window? I'll outline it step by step below...

For starters, render a frame of your scene with the lights at twice the setting just to be sure, unless you already have strong speculars..

1) set up a workspace as float just to be sure...
2) load your cineon using the import footage.
3) In the workspace window, open up the footage library and click on the footage child to enable the Footage controls.
4) under source, double check that its color only. Cineons don't use alphas unless they are DPX flavored.
5) under output, promote the depth to float... it should default to 10 bit.
6) Still under output, DISABLE THE "USE LUT"
7) attach a Bit depth converted to your cineon node, its under the color corrector operator
8) Under the settings tab, your input should say float. Under color depth output, put it to float as well.
9) Still under the bit depth converter, enable the LUT if its not already, and go to the LUT editor. there select Log -> Linear (this step is optional, I'll explain later)
10) Move your curser over the area of your output image thats blown out. You should see values over 1.0, assuming that your workspace is in float.

now, if you were to run a brightness or gamma/pedastal/gain operator on your image, you should be able to turn down the brightness and contrast of your image and resolve detail in the highlights. Its like playing with the exposure tab in the LW FP imageviewer. Awesome isn't it! Its like you are working off of a camera negative!! IMHO every 2D compositing package should do this, even Dotoshop! Fp renders is like working off of a negative, while 16 bit renders are like working off of a print or slide.

Step 9 is optional, since you can decide to work in log space and use a viewer LUT to look at your images in linear space. As a Log cineon files, its normal to see blown out highlights at like .8... that translate to like 1.3 in linear space.

As far as why this seems convoluted, its because of the initial settings in the footage library. If I had left the lut on, as it is by default when you load a cineon, and used the log-Lin conversion there, my highlights would be clipped. despite my image being promoted to float in the footage control settings, I would get my data clipped. By using a bit converter to force a supposedly already float image to float again, and then apply the log-lin lut there, I don't get my data clipped. To me this is counter intuitive, as the footage control settings seem to indicate that there is a bit converter and LUT curve that can be applied there. yet it gives different results...

to further complicate things, the Combustion user guide, page 484 explains floating point as using "a floating point number represented by a precise number between 0 and 1 for each image channel". My understanding of floating point is to support data below 0 and above 1.0... suffice range being -4.0 and 20.0.

Julian, for an accurate description of my methodology outside of combustion, go to the apple site and dl the Shake manual. I found the functionality of shake's I/O far more straight forward.

in shake, I can load a Cineon, SGI, or Tiff in float. My first operator would be to promote that file to floating point. From there, any LUT or color correction applied would never clip. Period. Shake has no boundaries in entering pixel values or anything. I found combustion brightness settings stopping at -100 and +100. I find shake the perfect companion to 3D image integration with the exception of 3D support. It can handle Z data, but you can't set up a 3D composite intuitively as you would in combustion or even AE

AE suffers from the inbreeding of Adobe. don't get me started on photoshop. Since I've use shake, photoshop is the little shop of horrors for me...

lemmie know if this helps!!!!

By Julian Johnson (Julianjohnson) (62.49.23.72) on Thursday, October 03, 2002 - 03:56 am:

Hi Arthur,

It helps tons :-). I followed your instructions and I'm just playing with gamma, pedestal and gain now and I have the full dynamic range of the image to play with which is ultra cool. The problem was really basic - I couldn't set the output of the source footage to Float because the float option on the popup menu was obscured by the bottom edge of the screen. Thanks for describing the process so thoroughly - it's so much better than trying to use the standard exposure controls in LW. I'll head on over to Apple's site for the Shake manual, too :-)

Thank you :-)
Julian