I'm trying to do a render of an office floor, and when I produce an image, so far I'm getting this obscure impact to the ceiling, and to a limited extent the floor (please see attached image). Can anyone explain how to stop this from happening, or will it resolve when I produce a higher quality render? I'm currently only working with medium quality renders as I will work to get all of the settings correct prior to taking the time to produce the high quality ones.
@henrysaxby you seem to have forgotten to attach your image.
If you are talking about dark splotches it has got to do with the lighting. These will reduce / get smaller / disappear if your increase the number of light bounces / up your GI settings. You can always marquee a small area of your scene and render just that bit using a higher preset to see if it goes away.
The medium and high quality presets will lead to very long render times.
Try to set up some very basic source of lighting your interior, this doesn't have to be the actual fixtures, there are also generic light sources you can add (like a big invisible sphere that emits light).
If there is colour bleed on your ceiling, it means you have a highly reflective surface set up.
For dark splotches, it is as Ling pointed out above.
You can try importing the attached rendering scene, which are the settings we use for reasonably fast interior renderings.
That is actually a good point. You can create faux light bounces by including extra invisible light sources. This would take a bit of skill and knowledge in order for it mimic actual bounces and not look artificial but the end result will be substantially faster to render. Ubisoft Montreal had a video showing off this technique being used in one of their games.
I wouldn't call my method particularly 'skillful', I basically mimic those big umbrella lights that photographers bring along: I put a light source behind the camera, just the generic sphere with pretty low settings. Just enough to brighten up slightly, without getting over exposure on windows with daylight.
I fake the light fixtures with a 'light emitting' surface (basically it looks like there is light, but it doesn't actually light up anything).
Thanks for all of your advice, I'll definitely give this a go! @Lingwisyer, I didn't realise the picture didn't upload, I'll try to attach it again now. I'm very new to doing internal renders in such large spaces (office floors) so there is a lot of frustrating experimentation going on!
You can see the ceiling grid, but not the white 'panels' behind them, but only in certain places.
It looks like you have some sort of light source on the desk panels, like a LED strip. I wonder if they are causing issues with shadow casting and what not.
Try using the renderscene I included at something moderate like 195x135 mm at 300 dpi for a picture. It should render relatively fast and try with the light source on and off to see if the weird spots go away.