By Sasquatch
#376898
I was wondering if I somebody could give me some tips pertaining to inserting background images. Whenever I've done exterior shots I've just imported a large jpeg and place it behind the building. However this technique never fares very well when I try to do interior scenes. Since I have to turn the EV down to accommodate the interior scene the exterior becomes a blazing white void (like in the 1st image below). However you can see the background reflects perfectly on the TV screen.

Bright white background in quick render (notice the TV reflection): https://www.dropbox.com/s/vfxxyhpz1ge7m ... 20room.png

How the shot has been set up: https://www.dropbox.com/s/9niqvgqr6938a ... 20room.png

I've turned the sun intensity down considerably (to 0.08) and the EV is 5, any higher and the scene is too dark.

Could somebody tell me how I could improve my backgrounds? Or is the method I've been using too cumbersome and counter productive?

Many thanks
By JDHill
#376902
A couple of things, but mainly, the most important thing is to keep in mind that the camera in Maxwell is designed to work exactly like a real camera, which means that it is both correct that you need to use a lower EV for an interior, and that light from a sunlit exterior will be very overexposed in that scenario, the same as it would be were you shooting the same situation with your DSLR. The thing is to try and ignore that until the rest of the scene is set up using real world values, and only then, to deal with it as you would in normal photography, but with the added benefit that you can tweak some things you couldn't in the real world, if absolutely necessary.

So first, try to make sure things are set up to mimic how they would be in the real world -- light wattage values, sun & sky intensity, etc. It is also important to make sure that materials are not using unrealistic values; for instance, even the whitest paint is only going to be in the 220-230 range in RGB; using brighter values than this produces unnatural energy levels in the scene (rays of light that would have been absorbed by a given point, aren't), and can produce slower rendering and fireflies in the image. Once everything is in line, and it is time to deal with the exposure issues, you can then use any number of different strategies from the real world of photography (just for example, here or here), with the additional benefit that if you really want to, you can unnaturally dial the environment down, and so forth.

Lastly, it is difficult to tell in this case whether or not you are using the Production render engine; the image you linked is quite sparkly, suggesting this may have been rendered with the Draft engine, though it is difficult to say, given that some of the lighting parameters have been brought out of their normal ranges.
By Sasquatch
#376927
The light bulbs are 100 watts (bulbs are actually flat discs), EV is 6, and all of the white materials don't have an RGB range higher than 220. If I bump up the EV to 9 the background starts to come in but then the rest of the room becomes rather dark. https://www.dropbox.com/s/3z7fr9dxmmv4o ... om%202.png Unfortunately my computer isn't exactly cutting edge (to put it nicely haha) so indoor scenes take a good deal longer than exterior scenes for me. Those two PS techniques you shared look good, if all else fails I guess I can just use those. Is there anything silly about my method of setting up a background (jpeg as a backdrop)? Or is there a much simpler way of doing this?

Also, I noticed you mentioned in another thread that version 3.0.1 has the grass not rendering issue fixed. How can I download this new version or update?
By JDHill
#376929
There is nothing wrong with setting up a backdrop (or Image Based lighting) like you are doing, if it serves the purpose. The only problem, here, is that there is simply no getting round the fact that you cannot expose for both dark & light situations at the same time. In a more simplistic renderer, that would not be the case, but you would not be able to get the feeling of real light in the scene, either, as you do with a camera, or with Maxwell. There has been another thread, in the main forum (here), discussing this very topic over the weekend, so you may want to take a look at that discussion, too.

The upshot would be, if you need to have sunlight streaming in through the windows, then I don't see many ways other than doing as the photographers in those tutorials are doing, and combining two shots -- at least you have the benefit of having a perfect tripod, and being able to change some values that are fixed in the real world, albeit likely at the expense of realism. As far as alternate approaches go, this type of thing can be much quicker and easier to deal with when using the Maxwell Render Suite, since there, you can render out different channels along with the main render, where for example, you would not render twice, but instead insert your backdrop directly, using an alpha, or material or object ID output to do accurate masking (a luxury that a real-world photographer never has, since those passes are generated by the renderer, which has full knowledge of the 3D scene, preventing the need to use manual or magic-wand selection).

Actually, it occurs to me, there may be a way of getting at least part of the way there, using the standalone plugin:
  • 1. Switch Manager > Environment > Type to Image Based.
    2. Set the Background channel to Disabled.
    3. Set the Reflection, Refraction, and Illumination channels to Active Sky.
    4. Enable Hide from Camera (and maybe also Hide from GI) for your backdrop.
Please note that the backdrop needs to be a group or component in order to enable those rendering options. With this setup, what you should get is your scene, with the backdrop showing up in reflections, but not being visible through the windows -- instead, you will just see black space there, due to the disabled IBL Background channel. Now, you can possibly put your backdrop into the scene manually in Photoshop, rather than actually rendering two different exposures. Lastly, if there is glass in your windows, you might try hiding that to reduce render time a bit, as it's not likely you'd actually see any reflections from it in this scenario.

So please give this a try anyway, and let me know if it helps.

Regarding 3.0.1, I'm not entirely certain on how access to the beta download site is regulated, but you should be able to download the plugin from this page. If you are not able to access that page, please let me know -- it has been my understanding that if you have the permissions necessary to post here, you will be able to access the page, otherwise I will need to talk to the web people about it.
By a.behrens
#376930
@Sasquatch: What you could do is to cheat: You could let flood more light into to room. Increase the window size for example and add a new dormer window. You can also remove parts of the room walls which are invisible for the current shot and you could add a a large reflector http://www.geofflawrence.com/lighting_reflectors.html behind the camera.

You could also add some curtains to break the direct light or put something (a large tree) out of the window.

And you could use different environment settings. If you increase the ozone (sky is more bluesh), decrease the atmospharic water (even more blue and lesser white) and decrease the turbulence you will get a sky as it was in our childhood. Then move the sun to a place that the sun itself is not visible through the window. With all that you will get a more overall light and lesser direct light and lesser overexposed areas on the floor.

What photographers do in such a situation is quite simple: The similar cheats and the wait for the right atmospheric settings. For example for cloudy days or the sun set.

If you want to reduce the render times for the required testrenders: Disable all objects but the walls/windows and use simplified materials without bumps/coating/displacements.

By the way: The room looks promising.
By Sasquatch
#376993
Thanks for the tips so far! You've both helped put things into perspective. I've been playing around with the settings that you both suggested. I seem to have the most success when I experiment with opening up areas out of frame to let in more light. I definitely seem to be put on the right track now, I just have to familiarize myself more with the settings in these tips and tricks. I haven't tried the PS and post production techniques yet though they look like they would help a lot, a friend of mine works a lot in that area so I will talk with him this weekend.

@JDHill I just uninstalled the demo maxwell suite and installed the beta of 3.0.1 and the grass works perfectly 8)

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