Renderman 23 Holdouts Tutorial

hello michael here from small robot studio with another renderman 23 tutorial today we're going to be having a look at how to do holdouts and composite uh cg assets onto uh live action plates still live action plates we're not going to do camera match moving in this one and this is going to be kind of a bit bootstraps we're not going to be doing anything exciting with matching the camera up to the back plate we're just going to sort of jury rig it and this will work fine for most cases i'm just going to show you a pretty simple way of setting up a couple of shots and lining up your camera fairly simply so this is the image we're going to be dealing with and we're going to put some see any cg element onto this and what i've done is i've got a reference for the size of the model that i'm going to be putting on on um in this particular example i'm going to be using tongue face if you've followed the channel for a while or if you look i've seen my instagram you will have seen them around there and also i've got this square plane here now i wanted to use something that was artificial because i knew that it was going to be nice and square as opposed to this chopping board which is made out of black wood which is obviously wood a natural material and has a tendency to warp and as good as you might be on a band sauce it might be a little bit crooked or you know it you might have sanded it a little bit skew if so it's nice to have a nice square object that you can use to light up a plane and once we've got that lined up then we can just go back to our reference that we're going to be using now you'll notice there's a slight shift between those two um that's if i was trying to line this up uh with this obviously it wouldn't work but fortunately this shot and this shot are actually lined up nicely and the camera just shifted slightly on the tripod when i took this photo but we're only going to be using this one for a lighting reference as well as the size and scale reference for our model so what you want to do is have your take three shots take one shot of a nice square object in your scene and then a reference model so you can post that can compose the shot in real life and then your back plate so in maya we will set up a camera so we'll go create camera and camera first thing we need to do to it is find out the focal length of the camera that you used i was using a 28 millimeter lens on my sony a7 ii in this particular example and if you're using a mobile phone oftentimes the equivalent focal length is 28 millimeters but you'll need to check the specs for your phone then we'll add in a image plane set create there and open our image so we're going to open up our square our image that we're using for the um to line up our plane to begin with now i'm just going to split the viewport down the middle like this and then on the left hand side we're going to make this camera one and so you can see there the image is nice and squared up but obviously the plane isn't yet now um i'm going to turn the gate on so we can see that a little bit easier and you will also need to make sure that the aspect ratio of your camera is the same as what your image is i already cropped this image to be a nine which is the same as 960 by 540. so um if you haven't done that just make sure you have before you go and try and do this now it is going to be a matter of getting this plane to line up with uh the top of this lid here that i just took off a box of whiskey if we're being completely honest now you can do it with the grid lines but i actually prefer to create a planer i just find it a little bit easier to see so we're going to go to poly modelling let's grab a plane increase the scale of it and we're going to go to plane [Music] plane shape sorry object display drawing overrides enable overrides and disable shading and now what we can do instead of trying to line the camera up to the grid and re because you can't resize the grid that kind of makes a little bit difficult uh we'll turn the grid off there and we'll turn the grid off there now we can just move this and then we'll move the camera up to get it a little bit closer something like that now we want to not rotate this as best as we can we just want to rotate the camera because we know that this is squared with the grid the my default grid so we know it's going to be where when we're chucking objects into the scene we want them to be flat with the grid as well um particularly if you're animating or something like that so we can actually just zoom out a hit bit here and our objective is just to get those lines to follow um the lines of the probably use the inside lines of that lid so now with the right hand view i can rotate the camera or tumble it okay that looks pretty close so if you're looking at the grid lines there following the inside of that and if you haven't matched up your um your focal length of your camera you're going to have a lot of issues because it's going to skew much more than it is in the image also it's worth noting that most cameras are going to have barrel distortion on them if you haven't corrected already so lines close to the edge and top of the screen are going to kind of bow a little bit you'll be able to see it just a little bit there with those lines it's pretty minor on that lens that i used even though it's quite old but it is it is apparent so if i'm happy with that with the camera selected i want to go to well actually we'll just double check we'll move this into position and i'll just yeah that looks pretty good okay so let's select the camera go to the channel box editor select all uh the translate rotate and scale values right click on them and lock selected and now this is so you don't accidentally move into this viewport and tumble the camera and that will throw your um your your alignment off and then you'll have to redo it and you're screwed at that point so you don't want to do that okay so with our plane in place what we're going to do is go to the channel box editor for the plane and i'm just going to change the subdivisions to one and now i'm going to line the plane up with the chopping board that i used here as the ground and it looks like our right hand side's a little bit off and it's a little bit skewed there so even though it was pretty good on that i might just line that up a little bit nicer so just quickly adjust that by unlocking those values and rotating the camera slightly now like i said it's a bit of a bootstraps way of doing it we could go into nuke and we could do uh camera matching or something like that um some people have recommended f spy i've got no joy from using f-spy with maya if you've seen anyone use it with meyer and have any success i'd love to see it i haven't been able to work out how to get it to work well um so i'm just going to do a couple of fine adjustments to this tabletop now and this is just to mimic the surface of that so um when the we've got the lights in and it's uh and it's lighting up this floor we won't see any weird um disparity between the edges of the the platform and the edges of the what the light is heading now we have a nice surface and we're going to create the holdout now um there may or may not be depending on what version of random n23 you've got and whether or not this bug has been addressed an issue with creating holdouts so when you create the holdouts the normal workflow is to select your object before we create it i'm just going to give it a material and i'll just call that uh wooden floor now you know what actually i'm going to use this one here because it's basically the same color as what the the um the platform is so we want to use a material that is a similar color and if you can obviously get used texture um to what the uh real floor is just so when you get light reflections um they are similar or as similar as you can to the type of material that you're getting so we're going to this is the button here to create a holdout so you want to select your mesh click hold out and if you get this error here that may mean it is not working correctly what we'll do to double check whether it is or not is create a severe and i'm just going to move the pivot to the bottom of the sphere and then move the sphere to the grid because i know the grid is lined up with the top of the um of the platform there um we will create a light and i'll just light this very quickly something worth noting when you're lighting your scene is particularly with these real world examples if you normalize the night lights can make it a little bit easier to balance the values of your lights out because regardless of their size you'll get the intensity will work the same it sort of depends on how you prefer the workflow i i generally would do that um just as i find it easier to think about but it's not necessarily the right or best way it's just for me it's the way that works all right so we'll just make sure that my renderman is the renderer and if we hit an ipr we should be able to see ah so you can see the whole that is not working and the light is probably not bright enough there we go so that sphere doesn't appear to be creating a shadow and we could probably change the back plate to the actual back plate now so we'll do that just by going in here under the back plate and we'll just open up the correct one which is this one we're not going to make this backplate visible in our actual render we're just going to composite it in after the fact so don't worry too much about it in at this point but what we'll need to do is select our object to try and get this to work go to render stats and we're just going to disable hold out render it and as you can see that has made it so the textured floor is visible which we don't want so we're going to re-enable the holdout re-ipr we will try clicking the hold out button again that may have done it rerun the ipr there we go um you have to fiddle around if you do it in those exact steps that should work for you so now we can see that we've got the correct uh the correct thing happening with our scene now we're going to add in an hdri image i've already taken an hdri of my apartment which which was where this was shot so we'll stick in a pixar dome light and we'll open up the image and i didn't shoot this in the same day it was cloudy and rainy when i shot this and this was shot on a nice sunny day with direct light so i'm just going to reduce the exposure to 0.4 maybe and we'll run the ipr again and make sure that primary visibility is off we don't need to see the background because the plate is going to be our background and then at this point you want to start looking at your reference image versus what you're getting out of the render and you're gonna try to match up those lights and shadows so in this particular image what i'm looking for is the light direction um it's coming from the right hand side it's nice and diffused and we've got i was using my phone to just give a bit of extra light on the right as well which is why it's a little bit warm so it's probably something like a 5500k light would probably be okay which is going to create that close um sharp shadow and then the diffused light coming from the sky is going to create the softer shadow here so i'm going to go ahead and add in those lights the one other thing that we want though is another hold out for the window because we're not getting any reflection of our ball at the moment and there's a window i but buttered this right up against the window so we'd have the reflection so we'll put that in now it's the same method as what we did for our um chopping board so we're just going to create a plane and we'll just rotate that scale now i know that it's butted right up against the chop chopping board so i just need to line that up which i'll do from the side and then just go back to our normal view and i'm just going to change that to be invisible as well or see through and we will want to make sure that it is not overlapping the door frame i'll tell you what i haven't lined this camera up very well um because i'm rushing uh because for this exactly tutorial so spend a little bit more time on it than i am um when i purchased this i did actually get it a lot better so learn from my errors and this i'll still be able to get it to work though for the most part so we will just continue on like i did it perfectly the first time um we're going to create another holdout with this first we'll add to i need to add a material to it and we'll just call this glass and it needs no diffuse and it needs a glass lobe with a refraction and reflection of 1.0 and a ior of 1.33 and we'll just check that that's rendering correctly it's probably having the same issue so we'll just try enabling the hold out oh that seems to have worked okay cool second time's the charm so we're starting to see a little bit of reflection there i probably want a little bit more reflection i'll put a backlight on there to get it to reflect a bit more but i'm going to go ahead and put in the mesh that i want and light the scene and then i'll show you what that looks like and we'll move into the next stage okay so you can see it rendering up here in the ipr i've added a few lights in and just fixed a few things with the camera so it looks pretty good the lighting isn't 100 accurate to what it would be in the lighting reference you can see i'm still getting a nice soft shadow which is what i want the values very close but i actually added in a nice little rim light as well just so he popped a little bit more against the background it was looking a bit dull otherwise i could go through and probably do a bit more to this and light link so i didn't get such a soft shadow on the ground but for this one i think we're going to call that close enough so we will now go through and do the aovs for this and just so you can see this is the setup so it's just the character he's pretty close to the window there i've got that back light there which is creating the rim and also helping to get him a little bit lighter on the back so we're seeing a bit more of that reflection in the background there um also i've got a large light and a small light which is replicating our diffused light and the light that i was using from my mobile phone you can see i've got the temperature set to 5500k which should be about the same um okay so let's do our aovs we're going to go into our render settings and go to render man and aovs now i did an aov tutorial last week and we're going to be doing something very similar here so we're going to create a lobe and we're going to call this passes because i can't think of a better name and we will just grab the director fuse direct specular indirect diffuse and indirect specular and pop it in there we do not need to get the emissive lighting as a pass because all we need to see are these here um the last thing we need is our shadow pass because we're going to be compositing this over a plate and i'm just going to create its own lobe there now for passers we're going to make those denoised and for shadow i don't believe denoising will work on the shadow but we will attempt to do it anyway i've got to do a little bit of investigation i'm not sure if this is if i'm doing something wrong here um i will update you in the comments if i can uh regarding this because the shadow is generally fairly hard to see anyway in the scene you don't really tend to notice the noise in it but you could always add a little bit of gaussian blur to get away with it if you wish this is only going to be the cast shadow we're not going to see the shadows on our actual mesh being in this okay two more things i wanted to bring up before we continue on i want to show the uh render again um i had something enabled that i'd forgotten to show if you have a look at the shadow here that is obviously incorrect because we're getting some weird artifacting basically it's creating a kind of border um whereas if we look at the correct render it should be sort of dark and more consistent the whole way around obviously this is not rendered as far as that but you can see it very clearly that that is not correct and the second thing that's not correct is that the shadow pass you shouldn't be able to see basically any of that so i don't know why it's done that i've done a little bit of investigating but i can't seem to re-create the same issue in a different scene whereas i'm using the same method i had previously and it wasn't doing this so i'm not sure why that is something to do with the shadow path specifically try changing the name of the scene didn't help either so what we're going to do to fix that is we're going to go up to the render settings we're going to disable learn light results that will fix the shadow and then output holdout map this is going to be for our shadow pass we're going to create it as a separate aov so now when we ipr you'll see that our shadow has not got those weird artifacts obviously it'll take a second to fully render up there but you get the idea well i'm stumped shadow pass is now correct and working so um maybe enabling that as a separate aav fixes the problem um it didn't previously but here we go living and learning live in the tutorial uh but you can see that that shadow issue is fixed there so if you're having that issue make sure you disable that learn like results um otherwise we'll keep those aovs as they are the other thing worth mentioning is the [Music] beauty pass if you want your other passes denoised make sure that you've got denoising enabled on your beauty pass as well otherwise it won't work correctly so we'll just go ahead and batch render this now all right here we are in nuke and we're just going to bring in our images i've just got them here in windows explorer so we'll just drag all those in and we'll also grab the plate okay now i've set the scene you'll see this format to 960x540 so i'll just need to reformat the plate to be the same as the root format and then we're just going to grab our passes filtered yep that one and we're just going to do the same thing that we did in the aov tutorial if you haven't already watched the aov tutorial make sure you do because it's going to show how to set up what i'm about to do okay so what we've got here is our beauty pass rebuilt and our shadow pass also rebuilt um this is quote unquote denoised it is obviously not very well denoised i'm not sure what the story is with the shadow passes and why they do not denoise i'll have to do some further investigation um into that and repost the result in a de-noise tutorial but if i find out before then i will make sure i put it in the comments for you so check down there or if you know the answer let me know down there now you were probably thinking the best thing to do here would just be to grab that and stick that underneath it and invert it that would maybe work but you're going to have some issues with the alpha particularly when you add in your backplate so what we're going to do and this is what i learned from reading the documents which if you haven't already you should always be reading the documents because they're just quite good nowadays as opposed to how they used to be about 10 years ago all right so we've got our shadow here and what we're going to do is keep that shuffle as is and we're going to need a merge this has to be a plus enter that shuffle and then on the other side we're just going to grab the beauty we'll just use the variance because it's just the alpha that we need out of this so another shuffle and we'll just grab the alpha out of all that side and then plug that into the a channel okay and then from our beauty composite we'll create a shuffle copy with one going into there and two going into there and then what we'll do is we're the rgba from that and the alpha from the second input so we're just grabbing the alpha from the side merged from the shadow and then the rgb info from the composite then we'll just create another merge with um a going into the shuffle copy and b going into the back drop plate and then if we hit that you'll see that that works correctly now and uh that is pretty much all there is to it um it's fairly straightforward there are obviously some hiccups involved and obviously i've been having some issues with the shadow pass i'm not sure why that is but like i said i'll let you know in the comments um if i have any updates to this tutorial um so far as the workflow goes but generally this will work for you then you just need to go in and i didn't put a crypto mac with this one but we could do a crypto mat we could sort out this shadow we could blur it a little bit using a cryptomat to um to sort of isolate it and uh then yeah we'd probably get a little bit better result and obviously you know at this resolution you can't really see it but if it was animating that would probably be a bit of an issue so we'd want to go through and fix that otherwise the denoise has done a pretty good job on our subject and there was only 128 samples so you know not massive uh but yeah that's pretty much all there is for this tutorial if you liked the tutorial make sure you hit the like button if you've got any questions or comments leave them down below if you want to see more of my work check out my instagram or the facebook page link in the description and if you would like to stay up to date with the tutorials i'm bringing out every week make sure you are subscribed for more content like this that's it for now though thank you very much for watching and happy rendering

Channel: Small Robot Studio

Views: 4,371

Keywords: renderman, maya, nuke, compositing, plate, holdout

Id: I_l5S0OW-q4

Length: 24min 59sec (1499 seconds)

Published: Tue May 12 2020