Full transcript
0:00hi everyone in this video i want to show
0:02you how we can render a transparent
0:04background and how we can do this using
0:07the region rendering instead of
0:10rendering a full frame so when
0:13you might consider disabling the
0:15background and having a transparency for
0:17example if your
0:19graphics card or system in general is
0:22too
0:22weak too slow to handle all of the 3d
0:26geometry you can then
0:28put
0:28a picture as a background in
0:30post-production
0:32so in order to do that you need a
0:34transparency here within the gloss areas
0:37to enable that we simply go to film
0:40transparency and we have to enable
0:43transparent glass
0:45the settings we've just enabled make all
0:47of the materials within our scene that
0:49include transparency and glass shaders
0:52within them well transparent so that
0:55means
0:56it will be possible to add anything
0:59behind them later in post-production so
1:02what you might want to do right now is
1:04re-rendering the entire frame but to
1:06save some time i'm going to press ctrl b
1:10and
1:10mark up this area so actually we don't
1:14have to re-render anything that's beyond
1:17it it's simply this kind of area we want
1:20to have re-rendered and transparency
1:23enabled actually i will press ctrl b
1:25once more and slightly decrease the area
1:29and you might wonder why
1:31am i not limiting this border region
1:33just to this
1:35glass area exclusively well the reason
1:38for that is since we've disabled the
1:40background the reflections within our
1:43scene will also change so you always
1:46want to leave this extra boundary so you
1:49can mask the details later and make the
1:52transition between the newly rendered
1:55region and the original image a little
1:58bit more smooth
2:00so here's our rendering result as you
2:02can see we only have the selected region
2:05rendered when i
2:07click my middle mouse button and pan the
2:09picture around you can see this checker
2:12here in the back stays untouched but you
2:15can also see upon zooming in that we
2:18have all those very slight
2:21shapes here and these are the
2:22reflections we had in our glass shader
2:25so that's pretty cool what you can also
2:28see is that we lack
2:29the environment reflections in all those
2:32surfaces as i mentioned the result also
2:35got a little bit brighter
2:37than the original rendering result but
2:40these are the things you should expect
2:42when
2:43disabling some of the 3d elements and
2:46preparing for the transparent background
2:49so let's now see how we can combine this
2:52result with the original picture in
2:54photoshop
2:55and before we jump into photoshop please
2:58remember if you save
3:01the results you always have to enable
3:04the rgba transparency here and the png
3:08or tiff file format or basically
3:11anything else except of jpegs because
3:13jpegs aren't allowing us to save the
3:17transparency
3:19with our original rendering opened i'm
3:21just going to drag and drop the region
3:24file to it so as you can see when i move
3:26it around we have this transparency
3:28visible so let's align the corners
3:32together
3:33hit ok here i'm going to right click and
3:36rasterize layer first so as you can see
3:39we have this border and that's because
3:42some things within our 3d environment
3:44changed and the rendered
3:46region is a little bit brighter but
3:48first
3:49we have to remove the actual background
3:52so to do that you can simply select this
3:55layer
3:57enable the eraser tool and just
4:00yeah
4:01paint it out
4:02from the image
4:05next step will be masking out the tone
4:07differences we can see so to do that
4:10let's
4:11add a layer mask let's switch to the
4:15black paint here
4:17let's make sure the mask is selected and
4:20let's use a very soft brush something
4:22like this maybe you can increase its
4:25size a little bit
4:27and yeah all you have to do right now is
4:30simply
4:31very softly trying to paint out
4:34the
4:35tone differences between those two
4:38layers
4:40so
4:41it's
4:42not gonna give you
4:44a perfect effect as you can see here we
4:47have this very clean uh difference of of
4:51tones but by increasing the brush a
4:53little bit
4:54and doing those very soft touches we can
4:57actually try to make it more
5:00uh smooth the transition here the
5:02biggest problem will be the fridge
5:04probably so here we would have to
5:06decrease the size of the brush
5:09and try to
5:11paint it out just by clicking multiple
5:14times
5:17so yeah this is one of the things you
5:18have to pay attention to when
5:21rendering regions and trying to make
5:24the transparent backgrounds you have to
5:27consider that the there will be
5:29illumination changes between the
5:31original rendering and the region when i
5:34click here you can see we have our
5:36erased effect visible so you don't have
5:39to be worried as we are using mask like
5:41this just
5:42switch the color to
5:44white and then you can paint back
5:47this area
5:49that you're not happy with so as you can
5:51see i'm just clicking here
5:54and making
5:56uh
5:57this layer natural again but i'm
6:00switching to black color again and
6:02trying to make this transition
6:04more smooth so you can see it's a back
6:06and forth process
6:08sometimes you just have to
6:10find a
6:12compromise between
6:14uh
6:15both of the effects so here within the
6:17fridge i think i'm gonna simply paint it
6:20out like that
6:22and if we zoom out
6:23well this area could look a little bit
6:26better but i think we can leave it just
6:28like that
6:30uh honestly
6:31as long as
6:33you weren't painting this region in to
6:36this original rendering you wouldn't
6:38necessarily notice there's anything off
6:40right now
6:42so the final step right now is simply
6:44adding the background image
6:46and it's going to be chuckle for hdr
6:48zero five a back plate from the hdr
6:51image as you can see i'm first dropping
6:53it to photoshop not directly to our
6:56image and the reason for that is if we
6:58have a big resolution change between
7:01images photoshop tends to crop or resize
7:05the pictures you're using
7:07and i want to keep my original size of
7:10this picture so now i'm just dragging
7:12and dropping it from this file to our
7:15rendering let's close it and let's move
7:18this layer to the bottom
7:20so now you can see we have it visible
7:23only
7:24here at the transparent area
7:26but the effect isn't
7:28that good and natural so we still have
7:31to adjust it a little bit
7:33what we can clearly see is the tone
7:36difference between the background and
7:39the rendering so let's add an exposure
7:43adjustment layer just above the
7:45background and let's simply use this
7:47slider to increase
7:49the
7:50exposure of the background image
7:53you might also play around with the
7:55offset settings to make it a little bit
7:57more
7:59not blurry but you know foggy
8:02and yeah now with this layer here on top
8:04we can move the background again
8:06and try to
8:08match the look we would be happy with so
8:11let's say
8:12maybe something like this maybe
8:15something like that
8:16um
8:18again
8:19one of the reasons i'm not the biggest
8:21fan of using the background images like
8:23that is you don't see it in any of the
8:27reflections so the result is not that
8:29natural to have this image in the
8:32reflections you would probably
8:34have to add it as an image in photo in
8:38blender sorry then render everything
8:41with transparency and only then add it
8:44uh here again in photoshop but i don't
8:46think
8:48there is any point in doing that because
8:52uh you could ask keep this image as a
8:54background in blender
8:56um
8:58as well so so you don't have to
9:00bother with playing around like this but
9:02there are certain scenarios with
9:05for example where you have way less
9:07reflections as we do in our scene
9:09where adding images
9:12in photoshop to the background is
9:15well it's something normal and
9:17everyone does it so let's say if you're
9:19rendering an exterior image
9:22then adding the background as jpegs as
9:26or as images simply
9:28is probably one of the best solutions
9:30instead of creating everything as a 3d
9:33model so yeah
9:35sorry for the long talk at the end of
9:37this video but i hope you find this
9:39technique useful and you will
9:41use it in your day-to-day projects thank
9:44you for watching thank you guys for
9:45watching this video is part of my
9:47interior visualization course in blender
9:49which you can watch for free on youtube
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10:11watching and i see you soon