View Full Version : HDRI on internal walls?

04-11-2011, 05:14 AM
Ive recently started fiddling with HDRI and am impressed with the results..
How can I use HDRI on an internal rooms walls?
Everything Ive seen (tutorial wise) is for lighting objects within rooms..
But, how do we light the actual room walls and ceiling using HDRI?
Im ending up with well lit objects in a room thats clearly not as well lit as the objects within it.. (using seperate passes)
What do i have to do to get HDRI on the internal walls?

Cheers for all help

04-11-2011, 05:33 AM
The easiest way is to remove the walls behind or unseen by the camera but this can cause reflection issues.

Just having the hrdi 'light' come in through openings is usually enough for me.

04-11-2011, 05:39 AM
You can't basically.

HDRI is used to capture a lighting environment surrounding sometihng, which can then be reprojected as if surrounding something else. Since teh key is the "surrounding" bit, then to use HDRI to light the inside of an enclosed space would require a way to capture the inverse surrounding.

Ofc, you can do this, but in order to light an interior, you have to first sample that interior, and then project the result back onto it, this of course, is self defeating.

What is needed therefore to light an enclosed space is a radisoity simulation. This solution can then be baked in different ways. For instance you may bake it as an image which gets rendered on a UV map of the interior space, which is then simply texture mapped onto the internal space... or you can record it as a cache, which is a recording of the ligght pattern formed within the space, and which can subsequently be used to relight that internal space time and again (as in over sequential frames), or stored and refined further with additional calculations as and when required.

04-11-2011, 08:40 AM
Got it by ripping out the unseen walls and rendering the remaining walls and ceiling seperately..
Problem i have now is that the walls have a white edging around where they should connect to the ceiling (ceiling rendered seperately) this is a problem i get a lot when rendering passes, Where the object meets the transparent background...
What is it, and how do i get rid of it?

04-11-2011, 08:49 AM
You have whats called colour bleed I'd guess. (Better if you post something we can see.)

By separating the walls from the ceiling you won't get the effect of light behaving naturally. Radiosity is clever but not that clever.

04-11-2011, 09:25 AM
Removed the ceiling as it was just too dark with it in the scene..

Anyway, heres the monkey from this scene and you can see the light border he has around the body...
No idea how to get rid of this, He has a relatively dark background behind, so this light 'border' which has appeared is obvious in the final composite
The only way ive found to get rid of this 'border' is to stick a black Jpg in the background but that messes things up in after effects..
Since ive started using passes this has been quite an issue..