Hello! I'm having one of those color space issues.

I'm attempting to get the color picker to pick the expected value as seen from the viewport. I've made a test scene using standard Houdini settings to illustrate.

In the attached image and basic test scene, I've enabled No Lights, and created a grid with a color value of [0.2]. On a sphere, I use the color picker to select the value from the viewport. The result is instead [0.3059].

From what I can tell, I have consistent colorspace settings in viewport and in the color picker. I have tried other combinations, including disabling the viewport openColorIO and changing the color picker display, view, and pick options, but none have successfully picked the expected value of [.2].

Anyone know what the trick is?

Hello. I noticed that when I set Diffuse color to {1,1,1} (press D key > Display Options > Material > Simple Material > Diffuse) and disable lighting in the scene you can pick the color value pretty accurately. I managed to get values {0.1973, 0.1974, 0.1947} with these OCIO Options:
Display: sRGB - Display
View: ACES 1.0 - SDR Video
Pick: ACEScg

I think it can't reverse ACES transform from a lossy 8 bit int to exactly 0.2 float. Interface gui is 8 bits per channel. 8 bit color only has 256 possible steps so each step is about 0.0039 jump in color (1/255). I'm picking max value of 0.1974 and the next closest step monitor could process is 0.2013.

And also if you are picking/sampling a color value of 1,1,1 it will return {0.977,0.977,0.977}. Now it's a bigger gap between the values because that's how ACES curve works, it holds back pure white to save room for highlights. In color steps it would be around 245 out of 255.

Aces doesn't seem to exhibit the expected behavior either. When using matching screen and picker settings for Aces SDR, The [.8,.6,.2] color is resulting in [.595,.521,.307].

Hello. There is a big discrepancy between our VIEWPORT colors. On the other hand, the color value you picked that's on the color pop-up window is almost the same in both our screenshots.

When I opened your file and picked a color from grid, while making sure Diffuse={1,1,1} in Display Options and lighting is disabled, I got these values (0.7781,0.5844,0.1966) which are pretty close to (0.8,0.6,0.2).

I also dug through OCIO Options in Color pop-up window and the only time I got very close (0.5341, 0.5106, 0.4208) to the values you picked is with these settings:
Display: sRGB - Display
View: ACES 1.0 - SDR Video
Pick: ACEScc (Must be ACEScg)

I'm attaching a screenshot so you can compare the look between our viewports.

Oh, I misunderstood your description to set Simple Material's diffuse value to {1,1,1}.

By setting the Default Diffuse to 1, I was able to find the settings that works for my use, it also appears to be the settings I needed to color pick from images, which is great. Not sure I understand the exact reasoning for this, but;

For sRGB display, and untone-mapped view, I set the color picker settings to:
Display: sRGB - Display
View: ACES 1.0 - SDR Video
Pick: Linear Rec.709(sRGB)

That results in a value that is almost the same! Good enough for my needs at the moment.



Thanks for your investigation Italimpex!

Did you notice that picking a color on different areas of the grid returns different color values? I found a solution to almost always pick the same exact color value (or with +-0.0039 accuracy) on different areas of the grid is to pick it with OCIO/ACES disabled. So for {0.8, 0.6, 0.2} it picks R values 0.7961 or 0.7922 (0.0039 difference). For Greens it picks 0.5961 or 0.5922. For Blues it picks exactly 0.2 or 0.1961. Deviations from this 0.0039 step start happening when picking values <0.2 and >0.8.

- Go to Color Correction tab at the bottom of the viewport, click on sRGB - Display to open the menu and disable "Enable OpenColorIO" toggle. That will also disable ACES 1.0 - SDR Video view transform
- In OCIO Options on the color picker, keep display as sRGB - Display but change View to "Raw" and Pick to "Raw" because we are picking the color in raw/no-ACES color space
- And again, keep Diffuse to 1 and no lighting

We've already solved this issue for the most part but I wanted to share this little experiment as well. It's pretty straightfoward, like I said, you could just disable ACES in viewport and pick color in that raw no-OCIO space.