Reflections override: Strange behavior - Bitmap on screen mode

[lupaz]

Hi,

Please, take a look at the videos below.

On the first video:
When I isolate the object the reflection looks as expected: screen mode.
When I exit isolation mode it becomes stretched. Why?

The object is a box with a reflective material.

On the second video:
An empty scene with a box with reflection and a bitmap on reflections override.
It doesn't look stretched, but there's a second image being reflected.
Is this normal?


I'm working with Max 2023 and Corona 9, windows 11.

Thank you.

[maru]

Hi, it seems that you are using orthographic projection (either in the camera you are rendering from or in the viewport settings). Environment maps may misbehave when using this kind of projection. The solution would be to switch to perspective mode.

Other than that, I would strongly advise to update to Corona 10 HF1 (or waiting for HF2 which should be release very soon) - https://corona-renderer.com/download

[Aram Avetisyan]

Hi,

Can you please attach the problematic scene so I can have a look.

I did not manage to get different reflections on a simple scene with and without isolation.

[lupaz]

Hi, it seems that you are using orthographic projection (either in the camera you are rendering from or in the viewport settings). Environment maps may misbehave when using this kind of projection. The solution would be to switch to perspective mode.

Other than that, I would strongly advise to update to Corona 10 HF1 (or waiting for HF2 which should be release very soon) - https://corona-renderer.com/download

Hi Maru. In both cases it's a perspective view though.
I will update to 10.

Aram, I'm sending attached a scene. This is the video of the same scene:

[Aram Avetisyan]

I could replicate this.

But, honestly, I don't understand the point of such setup. I don't even grasp how it works or is supposed to work.
Screen projection mode is mostly used for backplates, to have the images as is.

Is there a reason you are using such setup?

I have checked the behavior in VRay, there is no "double-box" effect and the results are maybe more "expected".

[lupaz]

The purpose of this is to have a quick way to have reflections on the windows without having to add a plane with an image behind the camera, which would give pretty much the same result but it takes longer to set it up.


There's another bug(?): It's with refractions override. It's affecting refractive objects even when there's no alpha behind. In other words, I have glass and there's a solid object behind; the image that overrides refraction shouldn't be visible at all. But it is.
See video below:
EDIT: Scene attached.

[TomG]

Since reflections actually head off in a 3D direction, it is best to use an HDRI or other 360 map for things like Reflection Override, as then each point in the image is mapped to a location in 3D space. This is why Screen mode does weird things, as the image is not mapped to a 3D space.

[lupaz]

Since reflections actually head off in a 3D direction, it is best to use an HDRI or other 360 map for things like Reflection Override, as then each point in the image is mapped to a location in 3D space. This is why Screen mode does weird things, as the image is not mapped to a 3D space.

Hi Tom,

Sure. Ideally a 360 or HDRI would be much better. But it's not always easy to get or find exactly what you're looking for.
In any case, I believe it would be best to have this working as expected if it's a quick fix for the Corona team. If it's not easy to fix I guess it doesn't matter.

The refraction override thing is definitely a bigger deal in my opinion.

[pokoy]

...
There's another bug(?): It's with refractions override. It's affecting refractive objects even when there's no alpha behind. In other words, I have glass and there's a solid object behind; the image that overrides refraction shouldn't be visible at all. But it is.
...

Reflection/Refraction overrides are tricky, I've run into it a few times too. What you're seeing might be the internal reflection of the backside of the plane so this might not be 'fixable' since it's not refractions alone. You may have to override reflections to black for it to be completely black.

[Aram Avetisyan]

The purpose of this is to have a quick way to have reflections on the windows without having to add a plane with an image behind the camera, which would give pretty much the same result but it takes longer to set it up.


There's another bug(?): It's with refractions override. It's affecting refractive objects even when there's no alpha behind. In other words, I have glass and there's a solid object behind; the image that overrides refraction shouldn't be visible at all. But it is.
See video below:
EDIT: Scene attached.

Remember that those are environment overrides.
So, if you look through a refractive medium and you see the environment/background, that is what you are overriding.
If there is a box behind the glass, you see the object (and not through it), so that is why it comes out black.
If you apply the same glass material to the object behind, you will see the refraction overriding map.

[lupaz]

so that is why it comes out black.

Hi Aram. If you look closer you can see that it's not black; you can actually see a dim image there.

[Aram Avetisyan]

so that is why it comes out black.

Hi Aram. If you look closer you can see that it's not black; you can actually see a dim image there.

Yes, as it's a box (double sided) and/or not fully transparent/refractive, but also with some reflectivity.

[lupaz]

Reflection/Refraction overrides are tricky, I've run into it a few times too. What you're seeing might be the internal reflection of the backside of the plane so this might not be 'fixable' since it's not refractions alone. You may have to override reflections to black for it to be completely black.

Yup. You're both right. It's the reflection of the refraction.
Overriding reflections with black doesn't do anything, but when I make the box just a plane, you don't see those reflections.