Colour of object effects hue of scene render output

[jason_witchard]

Hello, I was wondering if anybody could point me in the direction and advise me on what I am doing wrong. I have been using 3Ds Max for over 20 years but have only been using Vray for just over a year. My previous roles using Max have mostly been modelling but my job now requires me to produce product shot renders of the same product from different angles and finishes. The issue I am having is that if I take a product and change, for example, the fabric material, the whole scene changes hue. In the images I have attached I have only changed the seat fabric, but this is affecting the output of the frame of the chair and the entire scene. Everything in the scene is the same – I have only changed the diffuse material map yet this is effecting the hue of everything else in the scene. I have looked around this forum and around the web, but I don’t think I’m asking the correct questions and I can't find anyone with a similar problem. Thanks in advance for taking the time to read this, I’m quite sure I’m doing (or not doing) something simply stupid.

[hermit.crab]

Odd. I presume the new color affects the GI, but it does seem excessive. Try applying a VRayOverrideMtl to the fabric instead, where the Base Material is the colored one and the GI material is the old one. If that doesn't help, you could send the scene via the contact form so we can troubleshoot.

[robusto92]

What kind of material are you using?

[jason_witchard]

Odd. I presume the new color affects the GI, but it does seem excessive. Try applying a VRayOverrideMtl to the fabric instead, where the Base Material is the colored one and the GI material is the old one. If that doesn't help, you could send the scene via the contact form so we can troubleshoot.

Hmm, I'm not sure if I applied the OverrideMtl correctly but it didn't seem to make any difference. I have uploaded the scene via the submit a request. On doing so I received this Ai response (which I shall investigate):

AI Generated Response

This is a common issue in V-Ray rendering that relates to color bleeding and global illumination. When you change the fabric color, the light bouncing off that surface carries its color and affects other surfaces in the scene through indirect illumination.
There are a few approaches to solve this:

1. Use V-Ray Override Material: You can use the VRayOverrideMtl to control how objects appear in GI calculations. This allows you to have one material for direct viewing and another for GI calculations, which can help prevent unwanted color bleeding. As shown in the documentation, this is specifically designed for situations where you want to control color bleeding effects. V-Ray Override Example
2. Adjust Color Mapping: The color mapping (tone mapping) settings in V-Ray can help control how colors are processed in the final render. This might help mitigate some of the color bleeding effects. Color Mapping Tab
3. Use Color Correction: You can apply color correction to specific materials or in post-processing to adjust the hue of specific elements without affecting the entire scene. Color Correction
4. Render Elements Approach: Consider rendering with separate elements (like Diffuse, GI, Reflection, etc.) which would allow you to adjust the color of specific elements in post-processing without re-rendering. RGB Color Diffuse

This color bleeding effect is actually physically accurate - in real life, a bright red sofa would indeed cast a reddish tint on nearby surfaces. However, for product visualization where color accuracy is critical, you may want more control over this effect.

[jason_witchard]

What kind of material are you using?

Just a standard VRayMtl...

[fixeighted]

An option you could explore is to create a base scene and establish the lighting. This is your base render.

Use a material wrapper as an override material for the scene, set to be a shadow catcher, with whatever altered object excluded.
Use this for colour changes and comp the two.

This would give you a setup with the fewest settings to mess with and easy reversion to the main scene for whenever camera changes occur.

[DCHA34]

An option you could explore is to create a base scene and establish the lighting. This is your base render.

Use a material wrapper as an override material for the scene, set to be a shadow catcher, with whatever altered object excluded.
Use this for colour changes and comp the two.

This would give you a setup with the fewest settings to mess with and easy reversion to the main scene for whenever camera changes occur.

I vote for a tutorial on this concept

[fixeighted]

Really very simple - here's a scene to illustrate.

Switch the override off for the main render and turn it on for each colour change.

[DCHA34]

Many thanks. I'll take a look

[Vizioen]

Is your auto White Balance set to on?

[hermit.crab]

jason_witchard Thanks for the provided scene. As Vizioen suggested, the Auto-White Balance is active and overrides the Camera's color temperature. Disable it, and you'll get the expected results.

[jason_witchard]

Is your auto White Balance set to on?

Yes, it is indeed. Thankyou everyone for helping me out on this. I thought it would be something simple. Unfortunately, simple appears to be above my pay grade. Thanks again