OTOY Forums

So i am using a HDRI to light my scene and i want an image for the background, but the background image is not visible from inside the room or when i look through the glass/window. Am i doing anything wrong?

Thank you

Hi Pavel,

No, you are not doing anything wrong. This is just a limitation of octane/background images. You will need to add opacity to your window so that it has some alpha so that the background image is seen through it.
What you should see through the window is the HDRI, since this is actualy part of the scene.
Your best option is to use a plane for the glass with a good amount of reflection, and bring the opacity down utill you get the desired mix of background and reflection.
Also you can drive the opacity by a falloff map, which will give higher reflection at grazing angles which improves realism (there is a material in the liveDB that has this setup: Materials->Non-organic->Glass->"glass fake falloff")

The reason it is this way is because a background image has no place in 3d space, what part of the background would be rendered if light gets refracted on the way through the glass? What parts of the background image would you see in a reflection of a sphere with a mirrored surface? The best you would get is to have a location for the background image in 3d space, effectively converting it into an HDRI.

Hope that makes sense, it's a bit hard to explain!

Thanks
Chris.

Thanks alot! That helped and you explained very well I will test this now.