How to use Relighting in Nuke

[Music] well everyone my name is zoo Gator and this is you goes desk welcome to another edition of you just have to be better this time we're gonna talk about relighting in new let's just get started shall we so relighting a nuke is something very controversial the force now you should never use relighting a nuke if you have access to the cg scene and if you actually have enough time to relight or rerender your shot so saying this means that whenever you have the opportunity you should always go back to cg to relight or to do any kind of rim lights that you might need in side of your cg now taking into this account you're probably wondering why the hell am i doing this tutorial well it's very important for you to understand that a sometimes you don't have time to rerender again B sometimes you have no control over the CG so maybe the CG artist has finished his work so you have to do it yourself see you might not need actual properly lighting in this case that's the way that I use the most is when you actually need to just do a few little hints of color correction or maybe use a few bounce lights just to establish a few more creative choices in terms of the graving of the scene so really use relighting with caution otherwise it could make your scene look ridiculous very fast first thing you need for relighting to work is you'll need the normals bias and you need a position pass the position points know there's something that we discussed in detail on the video that you can click right now in the screen but basically once you have your position pass what you will need for this to work will be a node called the real light now this node is part of nukes through the system and as soon as you bring it in it has two different inputs now one of them is the light I'm just gonna put a normal light here so it's absolutely normal light color means the RGB of the scene so I'm gonna just plug this in and to my actual render news today we're going to be using one frame from the Assassin's Creed trailer that I direct last year if you want to see more about this trailer you can click on this link on the screen right now for you to actually check it out and you can also see the full breakdown of it on file of smokes website now as soon as you put in some lights and some color you can see that the real light now has another input which is Kam now I'm gonna plug this into my camera because you do need a full exported camera for this entire thing to work and last but not least you have a material in this case you have a choice of materials you can either use the diffuse material you can also use specular material for a Phong material or you can use a basic material as well which has a combination of both materials at this stage which is gonna start with a specular material so I can show you what this is so I'm gonna just plug in the specular to that I'm using two viewers here so that I can show you a bit better both things I'm also going to add the light pass into my light seen in the CG and I'm gonna put my viewer to that so I can actually see the light in my position pass here you don't see anything because the real like note requires you to specifically tell him where the passes are so I'm gonna choose normal spots from my list and I'm gonna choose my position pass from my list now these two passes are here because I have brought in all the passes into my stream before as soon as you do that you can actually see that there's something going on on the output of the real light now this of course is just a specular pass and the reason for the light to be below is because just like you can see on the 3d representation the light is in below so now this is why you need a position pass the position pass allows you to actually preview in real time you where you're putting this light up as you can see now I have the light in front of them and as I put it closer and closer to their face this kind of gives you a representation of where the light is so Atkins you can see now I have kind of a specular material and and the cool thing with this is that now I can create some nice rim lights so imagine that I decide I'm going to change this to spotlight instead of a normal light and I'm going to just basically direct the spotlight into them and so the cool thing with using spot is that now I can direct where I want to light up my extra light so imagine for a moment here that I want to do a rim light behind him so I'm gonna point the light to him I'm gonna lower it a bit more actually make it higher and there you go so this would be our mind my first rim light so now you're probably asking yourself why don't I just go to tweenie to do this well the cool thing with this is that you can do it much faster and also you can use it for really specific color Corrections that you're gonna make now once you're happy with where your rim is and at the moment you can see that there's an actual rim light it's a light that is behind the statues just like you can see here I'm going to use a shuffle node and I'm gonna put it into my stream so this would be my first light now remember we use the specular in here so now if I go to my stream as you can see here I have my direct and then I have my subsurface scattering then I have my reflection and then I have my specular no because I already have a specular I'm going to shuffle my new specular into the specular area of my composite reason I'm doing this is because I never mix things around it's always easier for your own sanity to organize yourself when you're doing these kind of things and now I'm gonna also make sure that I have my off channel and I'm gonna put a unpromoted and now I have my extra light now I'm gonna put a merge node with a plus and I'm gonna merge it into my other specular so now you can see I don't have just the specular pass that the CG artist gave me I have it a little extra specular so if I now look at the full comp this is just enough to just give me just a little hint of extra rim light and especially handy here if you want to actually intensify these kind of lights here and if you actually want to have a nice detail on the side there now one thing I should warn you is that when you're ever you bring in these kind of lights you have to careful with the edges because the edges of the scanline renderer don't really match the render the reason for that is because your scanline render will never be as good until is aided as the actual render so you see the render here looks very pretty it has a very good filtering system now the real lighting does not the filtering in the real lighting is much more harsh it actually does not match up with the edge of your CT so as you can see if you can pair it from one to the other it actually is not matching now it's very easy to for you to fix this the only thing you need to do is to use edge extend node so I I'm gonna use my favorite one which is the color edge and this should give me the ability for me to basically edge extend my I'm just gonna tidy up this a bit here so I'm gonna do basically just edge extend before I shuffle here now the mask of course should be still the same one I'm gonna of course invert my mask and so the edge extend is going to create extra edges around my CG that came out of new okay so now you can see that now as I bring it in into my shuffle node it shuffles out I don't need one promote it I do plus it in so now I'm actually using it to relight my scene but then because I'm promoting it now I actually have a perfect edge so you see that now I merge that extra rim but because I used the edge extent you can clearly see I'm gonna show you this in a bit bigger fashion you can see that the edge expand here the collar edge just fix that edge problem that I have here on the scan line so whenever you have a scan line issue with edges because of course that's normal it's normal because the scanline renderer and the relighting node is not as good as a tree as a CG render in terms of Antal ization so whenever you have those kind of issues just using a color edge you can find them in luca pedia you can use a color edge you can use an ex Ecstatic standards there's at least five or six different nodes and you CAPD that can do the same that's pretty much it now one last thing but I wanted to show you is that you can also add more lights and that's really handy for example if you want to put another line you could do two rim lights for the price of one so then I can if I put a scene here to see now I have light to not light to which is also on the bottom let's imagine for a moment that I decide to put light to as a little extra light maybe on this side of the cg so maybe there's two room lights maybe there's one on one side and one on the other side you see now I have an extra light which is the light that is actually bouncing in his face and you actually have a little bit an extra bounce light happening on that side now of course this is all created decision of course but now if I go back to my specular that extra light is now part of my specular light so now I have two lights of course you could it's it's up to you if you want to choose to just have one Real ID with all the lights together or you can actually render one relight per light and then have each of them individually shuffled copied into your comp and the main approach that you want to do on this is that you want to make sure that if you do a specular material you put it in the specular pass if for example you do a diffuse you put it on the diffuse pass so important for you to actually organize it like that because then when you're doing color correction you don't affect other materials because of course the bounce light or specular light shouldn't be affecting reflections so there's a lot of things like that but you know this tutorial is already going wait long so I just wanted to show you this really quickly and that it that is it really and so of course if you think about it it doesn't really mean that you need to use the real light node to actually relight that's really not what it is all about the biggest use that I use for this node is actually for color correction a lot of times you want to call it correct in 3d and not really just using masks and that very big fan of using masks and rotoscoping for doing advanced color correction it's much easier if you use the normals pass in position and the XenApp to do color correction because you were call correcting a volume your call correcting a CG object so why not use 3d tools for colour correction so using this technique that I just showed you really allows you to use very small spotlights in different areas too for example like you saw on that statue you can light up a bit of Enzo's face or if you want you can put a spotlight and light up a bit of a sword and it's fist so there's really a lot of ways and it's it it goes beyond using a little mask in 2d to just tweak the colour correction it really allows you to color correct in 3d and I think that's what I really enjoy about using this technique and that is it for me today thank you so much for watching and as always subscribe you just asked for more of these videos also follow me in Twitter you go see Guetta and please like the video and leave me a comment I would love to know what other techniques you might be using and what you thought about these techniques also if you would like to support me with $1.00 please support me in patreon so that I can do more of these videos more often well thank you so much for watching and I see you guys very soon on you goes desk bye bye [Music]

Channel: Hugo's Desk ™

Views: 43,443

Keywords: ReLight, Nuke, The Foundry, Visual Effects, VFX, CGI, CG, 2D, 3D, Compositing, compositing, The Mill, Hugo Guerra, Hugo's Desk, Gaming, After Effects, Tutorial, Training, Lecture, Escape Studios, FXPHD, CMIVFX, Be Better, Nuke Studio, FrameStore, MPC, DNeg

Id: VpQr5XUeoSg

Length: 12min 22sec (742 seconds)

Published: Mon Jan 02 2017