How to Render Clearly Defined Caustics using KeyShot

hey fellow key shooter welcome to this tutorial where we are going to have a look at this scene and more specific the caustics that you see here it's not going to be a step-by-step tutorial on how to create the entire scene but rather quick tips on how to achieve these kind of caustics without any trouble if you want to have a look at the full scene play with the model or take a look at the layered Photoshop file that I've used to do the post-processing of this shot you can go to my Gumroad shop through the link in the upper right corner and download it from there this tutorial is made in collaboration with render weekly the profile on Instagram that hosts weekly render challenges I'm not going to dive in the physics and math behind caustics but rather show some common examples so this one here is quite typical we have the glass we have the sunlight hitting the glass and then the light is being refracted through the glass and a liquid and focused into this caustic pattern hitting the ground playing on the floor in this case it's also what you see on the bottom of your pool or maybe your cat's smart water tank it's also used a lot in the jewelry industry where we have light being refracted and focused through the diamonds here and also in cosmetic marketing shots you'll see caustics used a lot to emphases and highlight the colors and the glass used in the packaging here's another example and caustics are not only caused by transparent materials it's also caused by very glossy and reflective materials so here we have reflected caustics from the metal parts on this packaging and here's a really cool shot where we get the caustic reflected caustics from the side of this car onto the ground and I think a lot of product renderings in general could be made more visually interesting and actually also more realistic if caustics were integrated when you start to look for it in real life you start to see caustics everywhere so it's something that you can integrate into in rings to make them pop some more and make them more visually interesting and also more realistic depending on what you are going for of course if we take a look at all these shots together we can kind of establish some prerequisites for caustics if we look at the materials here we can see that they are either transparent or they are glossy and very reflective so we have the glass the liquid and we have the glossy metal pots here on these cosmetics and on this car as well then we need the light to be intense and focused when we take a look at the shadows in all these shots we can see that they are quite sharp meaning that the light source is small and intense in the shots where it's a bit more soft like in this one here and this one here we also see that the caustics are less defined so if you want this very defined and very focused type of caustics you need your light source to be very small and intense and at last we need the we need something for the caustic to be projected on so here in this case it's the ground plane the same for the car yeah actually in all these shots and this shot here as well we have the wall where the caustics are projected to with these things in mind let's jump into key shot and get some caustics going here inside key shot I have the bubble important and I have some basic materials set up already and I've made sure to have both transparent materials and reflective materials s we just discovered is needed to generate caustics in particular we have the glass part with a dielectric material and an orange transmission color inside that we have the liquid that is a liquid material type with a hint of green in the color and then we have the metal plate here with the logo on and it's just a metal type with a colored appearance before going into the lighting and surroundings and everything there is one important thing to enable in keisha before we move on and it's in the project panel under the lighting tab but default the lighting preset is set to basic and we can see if we go a bit down that we have this caustics checkbox and it's disabled meaning that we are not going to see any caustics no matter what we do we need to enable this and actually also we also need some global illumination and we probably also need some ground illumination and we probably also need some or a bounces you see as I turn these up we start to see some kind of caustics here on the ground so we need to turn everything on and bump up the rear mount is instead of doing this manually you can also go ahead and hit this jewelry lighting preset and it's pretty much set up for you already if you have some specific needs you can always go ahead and say you can always go ahead and change that and save it as a custom lighting preset but for now the jewelry preset will it do so even though we don't have any elements for the caustics to be projected to we can already see it a bit and it's because and the ground plane or the diva ground plane in key shot picks it up as well but in my experience you get better looking results if you add in an actual ground plane and you also need to do that if you want to add some material through your ground plane so in this case I have a ground plane and also a wall that I want to project the caustics onto and you can see here in the geometry view that you can hide and show by hitting the geometric View button up here or hit o on the keyboard um yeah we can see that it's just two rectangular planes and nothing else the material on these at the moment are a diffuse material type with just a gray color same for the floor it's just a bit dagger you probably noticed when I turn these on that our caustics kind of disappeared and it's because they are at the moment blocking the lighting that generates the caustics if I go to the environment tab in the project panel you will see that we have our default startup environment and it's quite a contrast less and we don't have any small intense sources of light that we need as we discovered just before I can go ahead and create a new environment here and I can try and go to the HDRI editor add in a pin make it small maybe a radius of five and then make it really bright so maybe 250 in brightness and I can able this aim or set highlight option and drag it over here and now we start to see the caustics pretty nice so you can definitely use the HDR I to generate caustics but in this case I want to use a spotlight because I want to add a stencil to create my composition and in my experience the caustics also renders a bit faster using the physicalized so either a spotlight or an area light also when using the physical lights you get a bit more dynamic feel to the shot because you get a more visible fall-off depending on the direction of the lighting so let's go ahead and do that instead instead of using this environment I'm going to use this one I have set up already with a decelerated dark blue background and just a small rectangular pin for adding a bit of depth to the glass material here so you can see if I turn it off we lose that reflection here here and here and it just adds a bit of depth to the shape of this glass as set for this shot I have a spotlight I want to use so let me turn that on and you see right away how we get these really nice caustics both the refracted ones from the in light going through the glass and the liquid and we also have the reflective ones coming off this logo batch and you can see it here on the ground and where we have the dark areas from the logo we don't have anything so we get this really cool effect on the ground this Bud Light is a sphere that I added in from the Edit add geometry menu and then I applied a spotlight material to it and in this case the power is set to 16 we have a beam angle of 70 to make sure that it covers the entire scene like that and fall-off is point one radius is point two just to have a tiny hint of softness on the edge here so if you wanted it to be more soft you could bump this up that might be too much maybe five centimeters and as the shadow becomes softer you also see that the caustics becomes more soft so again if you want the clearly defined caustics make sure that your radius of your light source is small if I go here in the geometry view and select my spotlight right click and say move selection and go ahead and pick the glass as the pivot point like that you can see how the caustics updates almost in real time as I move this around and you can really quickly fine-tune your composition of your caustics and how they should look and how everything changes depending on the angle of this source of light so there has a lot of fun doing that but let me jump back to my previous setting and I like this set up here one thing I want to mention here as well is that caustics are also affected by above maps so if i zoom in here on the glass and right-click and select it first right click and select edit material graph we can see that we have two bond maps at the moment and what I want to show is particularly this Prust one here that I have just going around the glass to give it a bit of imperfection making making it look a bit more realistic and but if we take a look at the caustic here as well let me turn on the read region view so we utilize all the CPU power just for this area we can see that if we take the bump height for that down to zero that the caustics will also be more perfect and if I take the bump height up to one we can see how the caustics are now way more distorted so if you lack detail in your caustics you can try and go ahead and add bump maps to your materials and see what kind of effects you can create of course right now it's way too much when we look at the glass but just having something subtle as point one will also help to give it a bit of interest to your caustics or maybe a bit more realism again all depending on your specific and needs so this is all good let me go to my camera view here and to like my preset up main camera with a tiny bit of depth of field and let me update the environment so this is telling you that some changes has been made to this environment and it's using a low res version so just to see everything in the full resolution make sure to update this one and here we go we have our shot and we have some pretty interesting caustics if I go to the render settings give this a name and put it in a specific folder I'll output this as PSD 16-bit and for now I don't want to include anything I just want to show you and that once I go to options set a quality and when using the interior lighting mode so when you pick jewelry it will also pick the interior mode and that also renders caustics faster than the product mode so make sure that you also use interior mode and and I said it's automatically selected when you take the jewelry preset but when you have interior mode you can only use maximum samples or maximum time so let's pick maximum samples and in my experience around 500 samples is needed to get nice and smooth looking caustics so if I hit render in background you will see that it looks quite nice so in the beginning we have a lot of splotches up here and on the side here but once it gets time to rest up a bit more these will eventually disappear it's not a big problem at all these will go away with more samples easy peace right but they're seen as also quite simple with we only have diffused materials on the wall and the ground lane once you start to have a bit more complex materials or if you have large areas that have a material that has some reflectivity to it in my experience you will get trouble with caustic splotches all over no matter how long it gets to render and let me demonstrate that so let me stop this one and don't want to save it so I just stopped all right so let's see what happens if we add some more interesting materials to our wall and ground here for the ground plane I have prepared a material a plastic material with full specularity and with some roughness and bump maps if we take a look at the material graph it looks like this down here so just a single bond map and a single roughness map but it will look a bit more interesting like some kind of concrete surface for the wall I have also prepared one a textured one and again if I open up the material graph you can see that it's one with a bump map a roughness map and also a subtle displacement map for just adding a bit of depth or variation of the depth to that completely flat plane and already now you start to see some trouble we can see we get these splotches all over their scene so if I go ahead to the render options and select render in background once again we can see that we now have way more splotches scattered around the scene and maybe if you let it rest up for a crazy amount of samples it will be good but in my experience it's not really feasible so what to do when you get these kind of problems and this is a very common issue with the caustics there is no direct way to fix this but by doing a kind of workaround you can make it work quite well so let's go ahead and have a look at that so in this shot besides having these materials on the wall and the the ground I also want to have a brushed material on the logo batch so a table click on that and take my brush preset material here and when that one is loaded in you'll see that we lose our reflection or the caustics here on the ground and actually I kind of want to keep that so we can also see how we can get that back and through the work around another thing I want to do is to add a stencil to my spotlight so we have just this defined square of the light I go into my spotlight material and select the one with stencil as you see here only thing that I have done to this one compared to this one here is that I have added this rectangular texture and positioned it to only show the spotlight in this specific area what we see here as well is that even though we still get all all these caustic splotches we don't see the caustics coming from the glass and for this time being there are a bug I guess in Keyshia where with this blend with color is set to black and you don't get the caustics if I turn it up to white you see we get them but then also the effect is kind of it doesn't really make sense I mean this could be cool but I want this in this example so what are we going to do here as well and again the same workaround that we are going to use for for getting rid of these blotches will also work for getting these caustics back so this is the main lighting I want to have in my scene so the default model said I have renamed that to Maine to show your model sets you either pick this these two arrows in the upper left corner of the scene tree or you can take these three dots here left click and drag it to this side what we want to do is to create a version of the scene that contains our lighting and material as we want them and then we want to create another version that will generate the caustics that we are going to need you can do this in a couple of different ways either with multi materials that I have already and studios or with model sets when you do it with model sets you get the option to change the position of the lighting or maybe add in more light sources to generate the caustics and without having them interfering with the main lining of your scene so depending on how complex you want to do this mixing you want to go with either model sets or studios or maybe a combination in this case we're just going to do a another model set so I make sure I have my main one selected and then I hit this add model set and I call this main / caustic pass so I know it's the caustic pass for the main model set I don't want to link materials I want to be able to add some and some other materials to these surfaces and I want to include these four parts that looks good so I hit OK so here in the caustics pass because I made sure to unlink the materials I can go back to my original spotlight here so yes right now I'm changing the spotlight material for the one in the main I have to make sure to double click this new spotlight you can see that it's a number one so I can select this plane without the stencil and get my caustics back here I will also pick my ground and wall and I can change that back to the diffuse and but what I usually do when I don't have any if I didn't have any multi material setup is to open up the material library by hitting him on the keyboard and search for diffuse and pick this interior diffuse and put it on all the parts that doesn't contribute to the caustics so in this case we have the plate here we have the and most of the bottle actually generating caustics and but I don't want to get the caustics from the ground and the wall and this is the problem at the moment that the reflection of the perfect ivities we have from this random wall are costing all these splotches that will never rest up so I take the diffuse and add to the ground plane and the wall just like that and now you see how it already looks way better and then again I also wanted to have the reflected caustics from this piece here and I also want to keep the brass material finish but if I go back to the main model set I have the brushed finish here so in the caustic pass model set I can do whatever I need to do to get the caustics I want so I can pick this one and the plate material by double clicking on it and selecting the polished version and it takes a bit of time due to the fact that I have this place mapped they ran a weekly logo but once we have the polished version again we see that we get that on the floor the trick now is to render the caustic pass with the caustic turned on and render the main pass with the caustics turned off if I go to the main model set and go to the lighting tab here and make sure to uncheck caustics we get this it's looking pretty nice so let me go ahead and render that I select my render menu I go to the output settings and make sure to call this one main I will save it as a PSD 16-bit and I don't want to add anything here so maybe the clown pass and add to PSD so it's all collected in the same Photoshop file I want to render 500 samples that's good so let me add that to the queue yeah so I already output this so it asked me if I want to overwrite and I don't want that right now so let me just call this one main tutorial and add to queue then I go ahead and select my main caustics pass and now we don't see any caustics because we have disables it here so I make sure to enable it and/or pick the jewelry lighting preset and the important thing here is now to use the same settings let me call this caustic pass and then in the Photoshop file we want to include caustics pass a separate pass so we have that on its own layer we also want to include reflection and refraction and because we can use that in the post-processing process to enhance the look of the glass and the liquid and no need to output the clown again we have that already so with this setup and 500 samples for this as well I'm going to add this to the queue I can go and take a look that we have these two setups here the one with the main look with the main materials in the main lining and then the caustic pass just for generating the caustic now I'm going to output that and then in Photoshop I will be able to combine these two into one coherent shot so let's go ahead and do that my two shots finished rendering and I have opened them up in Photoshop I have the main PSD as you see here just a single layer with the main lining and then we have this caustic pass PSD with the RGB output of course and then we also have this folder of it render passes containing the refraction the reflection and the caustic pass and what we want to do is to wrap these three and ctrl C copy them and control we paste them into this shot here and that's actually all we need for the caustic pass we can now go ahead and close it down and just for your information these two these two raw outputs are also included in the file that you can download on my grammar out site let's close down the caustic pass and work with the file here if we take a look at the caustics they are looking quite dark at the moment and we don't really see anything of the original shot beneath what we need to do here is to select the layer and go to the blending modes and pick one of these in this group here so either Lydon screen color dodge linear dodge or liner color and there's no specific rule for what you have to pick but I find that the linear dodge probably is it's the one that makes the most sense for for putting your caustics on top of your original shot so when I do that we can see that we get our caustics without any issues or artifacts whatsoever it is a bit faint though but what we can do is to select the caustics layer and simply hit ctrl J to copy it and to make it look a bit more bright another thing you could do sometimes is looking really dark is to select the caustics layer go to filter and add a Camera Raw filter to it and inside that you can go ahead and play with the exposure and the highlight and white sliders and to get all the details out but be very careful not to overdo it so it's kind of burning out and you lose details and do this very subtle if you want to do it this way in my case if possible creating these multiple copies will yield a more naturally looking effect and to clean up your layer stack a bit you can select all your caustics caustic passes and hold down shift while clicking this folder button to group them into one folder and let's call this caustics and then you can of course go ahead and adjust to fill all the opacity and if you want to make it less visible or more visible in this case I want to tone down this reflected costing a bit because it's actually a bit unrealistic due to the fact that brass materials don't reflect these kind of focused caustics but I like to have it for the effect and let me add a layer mask to the to the folder the caustics folder by hitting the layer mask button and I can take a black brush let me make it soft quite big let me take the flow down maybe 230 and let me zoom out and then I can just draw on top of that just to fade it out a bit but still have it and very subtly in the scene so this is not related to the caustics directly but I can go ahead and do the same for the reflection maybe if I want to make those a bit more visible like that and the refraction as well take that change the blending mode - I don't know maybe screen see how that makes the liquid a bit more glowing or the glass that's actually all there is to it now you have full control over your caustics you can hide them if you regret and don't want to have any caustics you can turn them on you can do local changes just to the caustics and that's super cool to have when art directing your final shot all there's left to do is to do the rest of your typical post-processing process and I have done that in this file here called main underscore post and it's also included in the download in the file that you can grab on the klom Road shop if you want to have a look at all these layers and what they add to the final appearance and that's all for this tutorial I hope that it will help you to create some cool looking product shots with caustics in them if you use these tips for your render weekly challenge submission feel free to tag me and I would love to give it a look and see what you create using this tutorial and as always like and subscribe if you want more content like this in the future and until next time take care

Channel: Esben Oxholm

Views: 68,764

Keywords: keyshot, tutorial, keyshot tutorial, how to, training, keyshot 8, keyshot render, cg, cgi, 3d rendering, esben oxholm, freelance, esben, oxholm, rendering, caustic, splotches, avoid, keyshot caustics, render caustic, problems

Id: K0jHnoXhtis

Length: 30min 38sec (1838 seconds)

Published: Mon Apr 22 2019