Interior Archviz - Reflection / Refraction Override

[cjwidd]

Lighting a scene with only an HDRI, but glass (window) pane reflections are stretched, disproportionate, etc.

Thinking I should use a RaySwitch material to apply custom reflections to the windows so the reflections appear sensible, i.e. scene is lit with an HDRI of a train station, but it does not make sense to have reflections of a train station in the glass windows of a scene like this, e.g. office space.

Pretty sure this is a common problem, and I think I've articulated the basics of the workaround, but missing some details.

watch x1.5 speed

[James Vella]

Usually I just put the image I want on a plane, set it to self illuminate and place it in front of the glass and set object settings to not cast/receive shadow and not be seen by camera. While interactive rendering you can just move it left or right to get the alignment you require.

[sprayer]

You should post it in daily build section, I cannot install it to check but could you check standard bitmap loader how it works?

[cjwidd]

@james vella

I went ahead with a version of what you did, and instead of creating a plane and adding the reflection material to the plane, I just passed the reflection material directly into the Reflection Override of a RaySwitch material that was then applied to the glass windows.

The missing piece was enabling self-illumination. Why is that necessary?

[cjwidd]

@James Vella Where do you source office / interior backplates for this sort of thing?

[James Vella]

excellent, glad it worked for you.

I suppose it needs self illumination because its not being illuminated by the lights in your scene, with the added benefit of being able to control how intense the image appears in the reflection.

When it comes to back-plates I have a wide variety of different environments that I shoot on my camera in my down time. If I dont have something I need exactly I need ill just search for something online. Unsplash.com have some great high quality royalty free photography that I usually check first.

[cjwidd]

oh man, great suggestion, thank you!

[James Vella]

you're welcome :)

[cjwidd]

Tried both options and I think your method is far superior, e.g. self-illumin mat on plane (non-visible to cam, no cast shadow, no receive shadow).

Problem with the RaySwitch only method is it's just too cumbersome compared to just moving the plane in the viewport, as opposed to adjusting tiling, offset, etc. in the texture.

[maru]

Guys, do not use self-illumination as it ALWAYS generates some light and casts it into the scene, and you don't want that. Additionally self-illumination is sampled just like GI, so it may be noisy, as opposed to lights (and Corona Light Mtl) which are sampled in a much more efficient way.

So don't use self-illumination for this.


The proper solutions are:

Option 1) Plug an environment texture into your glass material's Reflect BG override and Refract BG override slots
See the bottom of this guide (it's a little bit outdated, sorry, we will fix it ASAP) - https://coronarenderer.freshdesk.com/support/solutions/articles/5000501978

or

Option 2) Create a backplate (like you did in the video), but use a Corona Light Material with "Emit light" option disabled. This will automatically disable light generation and disable shadow casting, so you don't have to touch the 3ds Max Object properties and at the same time it does not block environment lighting. It was designed exactly for this purpose.
See this guide - https://coronarenderer.freshdesk.com/support/solutions/articles/5000515605

Also, using the rayswitch material / map is not necessary here. It does not influence the reflections appearing in the material. It influences how the material appears in other reflections. (e.g. if you can make your glass panel appear red when reflected in other objects)

[James Vella]

Sorry I should clarify, I use a standard material with self illumination, thus not illuminating the scene. I dont use Corona materials for this particular job.

TBH I have used this method for years, and it has worked quite well for animations as well. Im sure the above method can work as well, however I stick with what is simple and what has worked for me - generally speaking. Feel free to experiment otherwise.

[cjwidd]

Unfortunately, it seems like you cannot control the position of the reflection texture using a UVW modifier with Option 1.