How do we set the correct Vfh_rgb_color_space and verify it?

[stevejjd]

Hi Chaos team,

I am setting up an ACEScg pipeline with V-Ray 7.20.10 for Houdini 21.0 on Windows 11, using the following build:

V-Ray: 7.20.10
Houdini: 21.0.671
V-Ray build folder: vray7.20.10_houdini21.0_stable_23250

My OCIO configuration is:

fn-nuke_cg-config-v3.0.0_aces-v2.0_ocio-v2.4.ocio

The V-Ray Frame Buffer is configured successfully through environment variables:

OCIO=E:/repositories/ocio/nuke17.0v3/fn-nuke_cg-config-v3.0.0_aces-v2.0_ocio-v2.4.ocio

VRAY_VFB_OCIO_INPUT_COLORSPACE=ACEScg
VRAY_VFB_OCIO_DISPLAY_DEVICE=Display P3 - Display
VRAY_VFB_OCIO_VIEW_TRANSFORM=ACES 2.0 - SDR 100 nits (P3 D65)

That part works correctly.

I am unclear about the documented VFH_RGB_COLOR_SPACE environment variable.

The V-Ray for Houdini ACEScg Workflow Setup documentation says:

VFH_RGB_COLOR_SPACE=1

forces export to ACEScg.

However, the Color Mapping documentation says:

0 = Scene Linear Rec.709/sRGB
2 = ACEScg

I tested both:

VFH_RGB_COLOR_SPACE=1
VFH_RGB_COLOR_SPACE=2

In both cases, after completely restarting Houdini and creating a new V-Ray Renderer node, the visible parameter remains:

Renderer → Color Mapping → RGB Color Space
Scene Linear Rec.709/sRGB

Could you please clarify:

1. What is the correct value for ACEScg in V-Ray 7.20.10 for Houdini: 1 or 2?

2. Is VFH_RGB_COLOR_SPACE supposed to update the visible RGB Color Space parameter on newly created renderer nodes?

3. What is the recommended way to verify the actual RGB rendering space in the exported .vrscene or render log?

For now, I have removed VFH_RGB_COLOR_SPACE and am explicitly setting each V-Ray Renderer node to ACEScg so that the scene contains a visible and unambiguous setting.

When I set the environment variable, I would like it to be seen in the RGB Color Space dropdown as being selected.

Thank you.

ocio_aces2_p3_v2.rar (416 Bytes)