V-Ray for Rhino and V-Ray for GH different exposure/color temp

[seltzdesign]

How can I get the exposure to be the same if rendering a scene in Rhino or rendering the same scene from a .vrscene file in Grasshopper?

Right now I do the following:

Create a scene in Rhino with a bunch of rectangle lights. Set up the exposure to certain values and hit render. I get the following image:



Here are the settings:



Now I go to V-Ray > V-Ray Rendering > Export VRScene and export the whole scene as a .vrscene file.

In Grasshopper I load the .vrscene file and set the camera and exposure to the exact same values. All render settings are set the same. All other settings are left at default.

If I hit render in Grasshopper I get the following image:



As you can see its a lot darker and cooler with a hint of blue.

Here are the settings:



How come the 2 are different even though seemingly all settings are identical? How can I make both the same?

Thanks.


Latest V-Ray 5.10.02 with a Nvidia GeForce GTX1080Ti with latest studio drivers.

[seltzdesign]

I think I found the error:



V-Ray for Grasshopper adds a light rig if nothing is connected. This seems to be some sort of sky texture, as it tints everything in this blue color.

I think if it is rendering a .vrscene file with "lights on" it should not add that default light rig. Why have a default light rig anyways? I think it creates more confusion than what it solves.

Or rather, shouldn't the background environment texture be part of the .vrscene file?

It seems like the Render in GH node ignores the background environment from the .vrscene file and adds the default light rig in there instead.

[Peter.Chaushev]

Hello, seltzdesign ,

When you load a .vrscene file as a Proxy in either V-Ray for Grasshopper or Rhino only its geometry, UVs, shaders and V-Ray objects (lights/clippers/fur) are loaded. Scene settings serialized within the .vrscene file are not read.
This means that even if the same proxy is used in GH and Rhino, the render output of each scene will be affected by their separate settings. The most noticeable ones are the environment settings.

V-Ray for Grasshopper uses a different environment background, as well as environment GI, Reflection and Refraction overrides when compared to V-Ray for Rhino, e.g:

• Background uses a Gradient texture
• GI override is a color (0.6038274, 0.7835378, 1)
• Reflection override uses C:\Program Files\Chaos Group\V-Ray\V-Ray for Rhinoceros\maps\BOX_6 (blured).hdr
• Refraction override uses the same Gradient texture as the background

V-Ray for Rhino by default uses C:\Program Files\Chaos Group\V-Ray\V-Ray for Rhinoceros\RhinoDefault.exr as an environment background.

You can adjust environment background overrides in Grasshopper by using a V-Ray Light Rig Simple component.

As for the color corrections applied to the render output, the Rhino and GH VFBs apply corrections independently of one another. To achieve identical corrections, you can simply save them and load them in each VFB as LUT corrections.

Kind regards,
Peter

[seltzdesign]

Hello, seltzdesign ,


V-Ray for Grasshopper uses a different environment background, as well as environment GI, Reflection and Refraction overrides when compared to V-Ray for Rhino

Can I ask why? Wouldn't it make sense to keep them the same?

I especially don't understand the GI override being blue. That means from the get go in GH everything has a blue tint!?

If there are certain defaults in V-Ray how come they should be different in Grasshopper. I don't understand that logic.

Hello, seltzdesign ,

You can adjust environment background overrides in Grasshopper by using a V-Ray Light Rig Simple component.

But you can't set the same texture, can you? I can't see a texture input for the background. I can use a V-Ray Light Rig Dome and set the same RhinoDefault.exr, but its still not the same as in Rhino because a dome is only half a sphere.

It's like V-Ray for GH was done by someone who is not part of Chaosgroup. Everything just kind of works differently and everything has different names for some weird reason.. :/

[Peter.Chaushev]

The Grasshopper scene is specifically set to use a different environment background and default material suitable for iterative parametric shape design process. This is also the reason why the default render action is interactive rendering and not production.

To load an HDRI, please use the Dome Light Rig. The dome shape is by default set to Spherical in Grasshopper.
An alternative method to achieve the same render setup in GH as in Rhino is to simply use the V-Ray Render in Project component.

With all that said, a redesign of the light rigs is being planned. Its main goals are expanding the functionality of the components and making them more intuitive to use.
Any further feedback you have will be sincerely appreciated!

Kind regards,
Peter