UVs and UV Passes in Nuke: PART 1 [Beginner]

[Music] guys welcome to this beginner video uh intended for people to learn how to use uvs uh in nuke and just kind of what a uv pass is a little bit about uvs in general and then you know some of the practical ways that we can actually use them so this is again this is a big beginner video i'm intending to make an intermediate video and then an advanced video about uvs because it's a pretty in-depth topic and there's all kinds of stuff you can do with st map and uvs in general on 3d objects and as a compositor so there's some creative ways we can use those in the future but this is more of a beginner video i've split it into basically uh two parts one goes in maya explaining evs and then the second part will go into nuke and check out some of this stuff so if you guys want the project file it's in the description below for free and you can download there's a couple assets that come with it so you can actually play around and follow along if you want in terms of using some of these images here and i've also provided one of the uh i've provided this car render for free just one frame of it from my full nuke 303 class and it comes with the uv pass as well so you can actually use this and learn the technique so without further ado i'll get into the tutorial so for the first portion that we're looking at here it's really just the fundamentals of cg very much so the basics but i just want to cover this part in case some people don't have a 3d background some composers actually have no 3d background but i really highly recommend that you you know know some 3d as a compositor as it's going to give you a really big advantage and you're going to understand where things are coming from when you're working in nuke so i really recommend you get into maya or blender or one of the other 3d softwares that are widely used and understand these concepts so we're just going to briefly cover this in maya as this is an easy way to explain what uvs are and then we're going to go into more about what we can do with them in nuke and why they're relevant to us as compositors so the basics of uvs is very simple uh so you have this texture that's wrapped onto this cube here and essentially what you're doing is you're wrapping a 2d image onto a 3d model so essentially what you have to do is take a 3d model and you need to unwrap it so this is the unwrapped model so you can see if you imagine like a piece of paper you know if you were to cut this cube up and flatten it this over here on the right is essentially what that is it's just it's just a flat version of the model and if i turn on the texture view we can see that we're mapping this this kind of colorful checkerboard texture onto this model and if we hit this button here and i select one of the faces you'll see that this face here when i'm selecting the top of the cube is actually highlighting this specific square so we know that that texture here so you can see the numbers eight one one two are being mapped onto the top of that cube so essentially just taking 2d picture putting it on on there of course you can manipulate uvs if you're into 3d software so you can grab this uv and i can move it around and it's not going to change the geometry it's only mapping it's only changing the way this 2d texture is being mapped onto that geometry so we can slide that around and now you see that the top here is 2 3 2 three three four and also what you notice is that the side here is a bit stretched and diagonal and that's because you can see if we turn off the view you can see that these lines are diagonal so we're trying to map a straight a straight image onto a warped uv so that's kind of a problematic area so that's not how you'd want to map your uvs you'd want to make it so the lines flow the correct direction so that's essentially what uvs are and so when you're getting a uv pass in nuke you're essentially getting this layout this kind of layout and you can remap a new texture in nuke onto this layout so if i have these cubes like this i can you know put a different texture and it's going to wrap on the different sides of the cube without going back into 3d and so the reason for this is because you can save time and production and if you want to change or add some texture to cg that has already been rendered you can just do it quickly in post-production and you don't need to re-render or go re-light anything you can actually just do it in nuke so that's the reason we want to talk about uvs and now we'll start to get into you know other things we can do with uvs and just a couple examples on going over it so as we covered in the previous section um this is kind of the same concept and we're just looking at this inside of nuke now so i've kind of just laid it out on top here as the 2d view and then we have the 3d object underneath so on the left side here we have the unwrapped cube so this is brought in from maya this cube and the cube is unwrapped like so so we can see the 2d layout and we can see the numbers on here so for example that again that top face we have the numbers eight one one two um and we can see those on the top here and and just remind you guys this picture with all the numbers that's just for referencing where things are on the cube it doesn't mean all these numbers they don't mean something special it's just uh it's just a reference texture so we can see that that's wrapped around the object here and on the right here we have one uh that's called a normalized uh uv uh layout which means every single face is mapped uh basically over the same image so all of them are mapped exactly the same way so if we change the image here it's going to change all the sides exactly the same so it's not wrapping around really they're all all the faces are exactly the same so that's a little bit less useful but this is actually important to know because by default nuke is actually doing this um with the default cube it's creating this uh norm it's called a normalized uh uv layout so again so this is kind of uh when i keep saying u and v this is what this is referring to it's just an x and y representation so x and y coordinates of a 2d image and the reason we don't use x and y we use the letters u and v is just because in 3d we're already using the term x y and z pretty frequently so it's just confusing to have the same letters so u is horizontal and v is that vertical line here so that's uvs but now we only want to talk about uh uv uh renders so we can actually render out a special image so if we go down here this is a cube that's been rendered so we just have a cube with a basic texture on it and we also have a cube the same cube with this special image and these images are i'm going to get into it more in intermediate video on how we can actually create these special ramps so these gradient ramps are basically telling nuke the 3d coordinate system even though you don't have a 3d model anymore so this is a 2d image rendered from a 3d object so we only have 2d images but this one is special so we can basically use this to wrap textures around the 3d model without having to actually load the 3d model into nuke so i don't need to actually go and load and bring the entire model in from maya so if this was a character or something more complicated we don't need to bring in the character uh model we just need to have a 2d render of the uv pass here and so with this uv pass if we plug it into an st map node we can switch the st map to switch it to rgb and essentially what that does and the reason we switch it to rgb is because this is saved in the red green and blue channel so we can see we're in the normal layer here which is the red green blue and if we switch from red and green we can see there's some kind of information in these gradients and so by setting that to rgb and plugging in a source which is another picture it will wrap around that object so you see uh we have a picture a 2d picture of some vines here and when i plug it through the stmap it's wrapping around that 3d cube without having a 3d model involved it's just using 2d so this is basically just a 2d trick and we can retexture 3d objects very quickly without having to render them so i can move this texture around if i go to here i switch the transform you see i can move these vines instantly and i'm not doing any kind of re-rendering or anything like that it's just a cheat basically and then we have down here just some lighting so we can multiply some lighting on there and that's just a simple example of uvs so you're like well why wouldn't we just you know take the vines and render these in cg and probably you would with vines because you're going to get better looking vines than maybe a 2d image but there are certain aspects that you might want to do in in compositing such as if you're going to simulate water running down this cube that's going to be an expensive thing to do and it's going to take you a lot of time whereas if this is far enough away from the camera we can take a video of raindrops on glass and then we could just put that on the cube and now it's going to look like the raindrops are running down the cube and we didn't have to go into houdini or do any kind of advanced simulation we're basically just saving time and saving money so again that depends on your shot it depends on how far away this thing is from the camera so if it's a hero shot and you're looking really up close you're probably going to need some 3d drips but if it's something that's a little bit further away we can use 2d tricks like this and save production time and essentially uh that's how you have to always think of things with cgs if you can save time save money uh you know and uh it's pretty important to think that way so uh this is another example um i've given you guys a free basically frame from my full class which is the cg compositing class some of you guys have probably already taken this class so this video is a little bit more in depth on the uvs but uh you know we have this is almost an eight hour class uh on cg compositing specifically so yeah so this is kind of uh just more on this so we have a car render so beauty um and this doesn't have any layers it's just a jpeg and we have a uv render of this car as well so we also have something called the uv layout which again i told you guys about with the cube but instead of it being a cube we can see it's just this car uh cut up into uh pieces and put flat so we can see all the pieces here and if we want to put for example let's say we want to put a color wheel on the back of this car here so if you look at the car let's say i want to put this picture onto the back of this car well i'm going to go here to the uv layout to figure out where to place it so i go to the uv layout i look for the piece and i actually unwrapped this car because i modeled it so this is actually the piece so i can place that cube so what i've done is i've taken the cube i've reformatted it into a square it's just a bit easier because these uv layouts are usually square so i've rent i've reformatted it to being a square as well and then i've just transformed it and we can basically just move it around and i can oops i'll grab it here put it on the back of the bumper and now if i run it through the st map so i plug in the uv render and i plug in the picture that we've just placed and i've used this you see i'm doing two different things here i'm using this as reference like this kind of merge over here and on the left here i'm actually doing the the uh st map so this is just for reference that's all this is for so we transform that and we can st map it and you'll see we get this result where it's folding on the back here and if i merge that picture this result from the sd map over the top of our render we can see that's been placed on the car and we can of course move this around so i can take the transform uh hit use up and down arrow keys and slide this around and it's going to wrap around the cg model and again we're just dealing with two 2d images we have the the beauty render of the car and we have the uv render so that's pretty cool um so one thing you might be confused about is you look at this thing and you're like well i didn't unwrap this model and if you have a really complex model you might have a lot more pieces than this you're like well where do i you know how do i you know if i want to put a color wheel on the top of this this tire here you might be confused when you look at this picture and then you're going to be moving this color wheel everywhere like well i don't know which piece is is the right spot to put it and that's where this tester material comes in so that's where that material we've been using if we plug that in to the st map and we just let that go around the car that's why this material is useful is because we can see all these colors and they correspond to this picture uh in this square image so for example we see this uh 3 here and a 4 three and four next to each other the three is white and their four is pink so if we look at this thing where is the three white and four pink well it's right here so three and four right here and if we go to the corresponding place on our uh template we see that that area is right here so that's what that's just telling us it's just telling us where on this thing uh it's gonna land so three and four so if i put my color wheel over in that spot in the three and four and then i plug that into the st map you can see that is being wrapped onto the right place so that's that's what the tester material is for it just helps um if you if you don't know where to place things and that's one way to do it there's many ways but yeah so hopefully that helps out some people and we can slide it around here and that's how it works so this is again it's 15 bucks if you guys want a full uh cg composing class which has a lot more detail than this about different things this is one aspect of cg compositing i'm going to make another video more intermediate uv uses so we're gonna get into more advanced stuff uh how we can actually generate these uh use expressions to generate these patterns and eventually after that i have some plans to do an advanced uh uv uh video on youtube which is gonna be things that even senior compositors will probably benefit from if you're a senior compositor following this channel so i kind of have a range of people here so i'm going to try to post beginner and intermediate content most of the time and occasionally post you know uh senior level uh tutorials out here so that people can get use out of it so if you guys liked the video hit the like button and it helps out a lot and thanks for checking it out

Channel: Compositing Academy

Views: 20,821

Keywords: nuke, compositing, uvs, uv pass, stmap, tutorial, training, academy

Id: wb1WjHlXbn0

Length: 15min 52sec (952 seconds)

Published: Fri Oct 16 2020