Great Looking Caustics in Redshift (Redshift Tutorial)

hey nerds I'm gonna go over some of the settings to get caustics up and running in redshift. So I'm just using cinema 4d here and I have a basic scene set up I've just got a sweep background which is just a plane with a bend deformer on it. Got a camera set up to 100 millimeters here and a dome light with an HDRI in it but I've got the exposure turned way down. Like minus three, and I just want to do that just to get some of the reflections going in the glass objects we'll be making. It's not really contributing much light to the scene. I'll do a test render there it's just dark gray. I also have a center target null I'll use for a target for the spotlights and objects will be put in the scene. All right, also I've got a just a basic dark gray material here dark gray and the diffuse and I've got a weight in the reflection of zero. And I have that applied to the sweep. Also just want to go over some of the render settings here before we get started so you know where I'm at here I've got the samples min set to 16 and samples max up to 256. I've got a sample override on the reflection of 1024 I've got GI turned off for now don't need it. Yeah that should be it. Oh I also have some AOV set up here so we can just take a look when we start to clean up these images start to try to get the caustics to be less grainy I wanted to use these as an example to show just sort of isolate the caustics from some of the other passes so we can take a look at that a little bit later. Alright so let's go ahead and put just a sample object and see and I think we'll just do a basic cylinder for now and I will turn on the fillet for the caps and just do a subtle little roll-off on the edges and just do a basic Redshift material and apply that to the cylinder. Then we'll go up to add a spotlight into the scene I'm gonna right-click on the spotlight go to cinema 4d tags and down to target and grab my Center target null into the target object and now I can move this spotlight around and get this lined up so it is a good spot for our cylinder. There, something like that. All right. Do a little test render here and we've got this crazy thing. Here, let's ease this up a little bit more oops all right okay we've got just the basic material on our cylinder and a spotlight on it let's go into the material and we can use for now just use the preset for glass and let this update and now we have a glass cylinder in the scene alright so in order to get caustics on this we have to do a couple things we need to add a tag on our cylinder we're going to go to cylinder right click on it and go to redshift tags redshift object and down under the visibility tab or section you want to click on override and down here cast caustic photons we want to check that on alright and if we do something now rerender we'll see that doesn't do anything we need to go up into the spotlight and turn photons on for the spotlight and under the photon section come down to caustics emit caustic photons we want to check that on now do a render take a look here and we've got something all right and it's pretty rough we can see here there's lots of grain the default settings aren't giving us a clean render at all alright so a couple things we can do to fix this in this scene here these caustics coming off of this cylinder are pretty basic they're just sort of rounded shapes so one thing we can do up in these settings up here up in the redshift render settings we can go to actually before yet let me just save this over the picture viewer we have a reference here okay so we go up over to the redshift settings under Photon we've got some options here now you see this here max number caustic photons this seems like something you'd want to adjust and change and get a better result but actually this is tied to the caustic search radius down below and I'm not really sure exactly how this works but this has something to do with the number of photons that are stored in the limit for the search radius and affects how many of them are averaged out when you adjust this number it's recommended to just leave this as the default this isn't going to really change the look of these at all so let's just for an example take this caustic search radius from point 1 up to I don't know like 5 crank it way up here I do a rerender okay so big difference let me stop this and send it over to the picture of you are so we can see here before after big difference but if we zoom in no we're already at 200% let's go that's good 400 you can see there's some I don't know if you can see this in the screen capture but it's it's smoother but we still have this splotchiness here so all this is done is basically just blurred the results from this image so that's one way to do this and you know it's not too bad if you're this is just one object in a scene this can be the way to go just leave the render times low keep the number of photons in your in your lights that pretty low and call it a day but let's see if we can get some better results here by putting this back to the default and let's crank this that let's add another 0 on to this and re render this and see what this does so we have 10 times the amount of photons in the scene and let this finish and then we'll send it over to the picture viewer to compare alright so now this is with ten times the amount I'm going to hundred percent again ten times the amount as this one and it's a big difference so and the render times see what was this there's ten eleven seconds it's a little bit longer but not too bad let's do it again just add another zero on to this so that was eleven seconds let's try this one okay so that rendered in 23 seconds almost 24 seconds send it over to the picture viewer we can compare alright I believe this is was this one million? ten million? ten million photons. Let's go back to the Picture Viewer. Okay two hundred percent we can compare alright so this is ten million photons 1 million photons so it's a pretty good job so maybe bouncing back and forth if this is close enough maybe now come up and take the search radius to you know 0.5. rerender this and see. okay so this is 22 seconds for this render we've increased the search radius to 0.5 okay and over the picture viewer and compare so this is with a point 5 search radius you can look here little grainy and see a little bit of noise see here smoother results it could be okay now this is 200% as well so I mean go back to subtle difference looks a little dimmer with the smoothing on point 5 smoothing you know averaging these things out they get a little bit duller there is something you know I want to check this out here let's look at this little closer because there are some I don't like these little fragments don't think she'd be there but I think it's because of our subdivisions so I think we're seeing that faceted polygons of our cylinder so under our object tag let's go over to geometry we're gonna override the geometry click on enabled for tessellation and we'll use some of the redshift built-in smoothing on this we're going to take off screen space adaptive and just take this to like let's do two. take this to zero all right let's render this again and see what we get see if that fixes that kind of like I don't know striation in the caustics okay yeah big difference let's send us over the picture of you are take a look okay so big difference here between that completely different result interesting okay so let's maybe add something in here that has some more gives them a little bit different pattern into this okay all right now let's do a render okay so we've got some patterning here and let's take a look at that a little bit more interesting than before alright so let's go back up and take the search radius back down to default 0.1 and under the spotlight we've got an option here called intensity multiplier what I want to do is just bring up the brightness of these caustics here the caustics pattern so let's take this up to like three and this over a little bit okay and let's do a rerender okay so 30 seconds for that render big difference so we can see here increasing the intensity multiplier made this brighter but it also you know brought these other very minor subtle little caustic patterns here up a lot brighter which also increase the noise here so we can now see a lot more graininess in this than we did before so that's kind of the downside to cranking this up you're kind of cranking the gain on all of this stuff and so you're gonna get more of this noise introduced so the option then is to you know need to go back and blur this out which I kinda don't want to do because we can take a look but you know this pattern over here is nice I want to keep that the more we crank this up to clean up this noise the more we lose this subtle patterns has become blurred so let's try let's take this down to two so it's not so bright and we'll double the amount of photons in the scene we'll just take this up to guess twenty million I think that's what that is yeah 20 million turn to this and take a look Ok we've got 43 seconds on that one so we've gained 13 seconds from 30 seconds up to 43 we go from this to this so dimmer obviously and a little cleaner but we still have some noise in this and if we go over to I can use the layers on this but if we go over to the a AOVs we have setup here we can look at just the caustics for this and we can see in you know if you can see it in the screen capture so sort of isolates here the noise in the caustic so I can see here we've got some graininess in here so you know maybe 0.1 let's try 0.3 and see if this will clean it up enough take this back to beauty in here render again okay 41 second so actually rendered a couple seconds quicker and let's go back here and compare the two so this is the new one and that's the old one so things do get a little bit dimmer and a little blurrier see not much though so it did a pretty good job of cleaning this up but would you sacrifice a little bit of that brightness so caustics like in this case you know caustic stir started the show we want to showcase these things do we then have to crank up the brightness a little bit more you know find that balance again so that's sort of the basics of caustics at this point so what we have is you know a light that has photons set to emit caustic photons the object any object in the scene that you want to emit caustic photons and that's either reflected off of like a shiny surface like Chrome or you know silver or refracted through it or both of glass I can show you here let's do another we just change this material from glass over to I don't know let's do copper and we already have the tag on there so it's already visibility caustic photons we'll do another test render so you can see that no caustics is also the reflected off of like shiny chrome or something like that in this case copper okay there we go so 37 seconds that's over the picture so you can see here we've got caustics on this as well reflection off of this shiny copper still see the you know the noise in this and to me I think this is just a little bit too noisy if this was for a production render a final render probably would want to you know add like at least double or triple the amount of photons in the scene were this close to it rather than blurring it because I think what'll happen is we just get that splotchiness that you know these little the granular pattern here just becomes bigger so I tend to just, if I had the time, just crank up the photons in the in the light and then just wait for it to render especially if it's this close you know if you have a bunch of objects in the scene that are further away you can get away with just blurring them out not noticing them as much I did want to mention so if we go back over here to glass and instead do tinted glass we have a red color here I'm just I guess when you just get a little bit more I'll go to let go green and let's try this out and this is really just automatic so we're gonna get the color of the absorption I guess the transmittance color in this case of the glass is going to automatically create a colored light pattern on the on the ground the caustics will automatically take on the color of the material they're passing through there's no extra step to set that up there we go okay forty seconds and over to the picture viewer you can see they just have a green tint to them and no extra step that's already in there in fact you can even, if you wanted to, now let's go and do a ramp, if I can spell it right right and we'll leave it as a UV map and go orange to bright blue, pull these in a little bit so there's more of this we use this ramp to drive the, let's see here transmission I think refraction transmittance I think is what we want let's go back and check go down here to the color right all right grayed out so let's give this a render okay so we can barely see that let's take this absorption scale up to five try it again okay so I've got the the twist on this that's twisting the u-visa round that's weird it's good to uh a lot doesn't matter and you get the point so we've got both attest this over the picture viewer it's weird so we've got this both the orange and the blue patterning here from the glass coming through in the caustics pattern it's kind of unexpected and expect it to do that alright anyway you so that's automatic you get the color of the material will pass on the color to the caustics that's all automatic now couple of things that did affect the caustic so it's kind of difficult sometimes to know what you're looking for if you wanted to have a scene that you know had a bunch of caustics on it it's kind of it's hard to imagine like what's going to produce the best results so sometimes you know you think oh it's gonna be crazy and ton of things are on the scene is just like one simple line you know all the lights collecting in one area so the index of refraction plays role in that as well so if we crank this up to light and on 2.5 you know something close to the like diamond and then give this a render here we'll take a look and see the different pattern that comes out from this so we can see here a completely different pattern than we had before you know changing that index of refraction has a significant effect we also have an option here and go back to just class and option for dispersion and what this does is affects the way light is split into a spectrum as it travels through this material and so you think like oh I'll just try a little bit of it but actually if we if we go to like one it's going to be a tremendous amount so the way this works is very very low numbers is an extreme amount of splitting of the light a value of zero is it's not valid so it's just turned off so a kind of a standard range I think it's between like 30 and 70 so if we do a little bit here let's go to like you know like maybe 37 that's fine okay and we'll render this and take a look all right so over the picture of you are and see here we've got this nice sort of rainbow effect that's happening on these caustics so we can find this I don't know if I have one of our that cameras say yeah there we go so from this to this you can see this sort of splitting off sort of the expansion of these caustic patterns here and then this rainbow effect that's happening we can try it here an extreme number which is like you know like point seven do it again whoo what all right looks like that is crazy so that to that it's wild all right let's do you like six let that rerender oh and if you're interested in matching real-world values to a material for dispersion I believe the value there that you can Google is I'm not trying to pronounce it it's spelled a b b:e abba if you look up if you do a Google search for that or material or refractive Abba the hell you you able to see there's some charts online that have example numbers on there alright so this is ready just in their backs and see it's nice beautiful and that was the setting of 6.3 then we crank this up like that this in this area 60 is almost off again it's very very subtle okay oh another thing that affects this so right now I've got this glass is set to a roughness of zero this is perfectly clear so let's go back and turn off dispersion let's turn this off as an example so if I increase the roughness a little bit not that much just something that adds a little bit be like that's fine and just person is off okay and render this half again this is also something that's going to affect the clarity of the caustics how rough the material is and I do have the the roughness of the reflection is still tied to the roughness of the refraction transmission so we'll see the difference here in a second let this render you can see here we've got this sort of blurring effect happening with the I don't you know this sort of frosted glass look and this is a little bit extreme that's probably not realistic but you know it's not also realistic to have it a hundred percent perfectly reflective either so this is sort of a way to you know if you're looking for extremely realistic caustics you know that search radius function you know it's right now it's set to 0.3 but it you know a more realistic thing may be something more like this the sort of blurred or blurred settings so you know cranking this up may not be a bad option sometimes you know it's if you're going for maximum realism so right now what we have is just a spotlight in the scene and pretty good results with this I'm gonna set this back down to the roughness I mean back down is just a very small amount now what if we have a scene that's already set up we want to add something with caustics into a scene with more complex lighting we've got area lights we've got HDR eyes turned up so let's see what happens here let's turn off our spotlight and take our dome light go back over and crank this up now caustics should be off we don't have anything emitting caustics anymore so we turn the spotlight off and even though we have caustics on for the object there's nothing and meeting them in the scene right now because I don't have caustics turn on for the dome light and that looks pretty dull this is red tape it's dumb light zoom out here and see try this on let's take a look here at our I've seen we can rotate this around whoops I don't like rotate this around to get some better lighting all right there we go let's try this why yeah all right so let's say this was perfect what is this sort of lighting here very supersoft and another thing we can do here in the material is take our shadow will pass the up a little bit it's kind of unrealistically low I think it might be realistic I don't know but it seems like things should be a little bit darker clear glass should have a little bit more shadow to it so that's under advanced settings of the material shuttle shadow opacity you just crank this up until it's not like you know tell it's completely dark but just move this up a little bit okay so let's say we have this scene lit with an HDR I'm we want to add caustics to it problem is that a photon here turn off this render turn it on and go back to what we had before what was like 20 million it rendered and about there's about 30-40 seconds and we'll take the intensity multiplier up to to what we haven't yeah so it's like the same thing all right so we've had the same photon settings the objects the same let's take a look and see what this this gives us right back here turn this on and turn on bucket mode okay a brutal two minutes 14 seconds up from what 30 seconds there's last ones so and what we have here I should close this too soon is a mess we've I mean 220 million well we have 20 million photons in the scene on this dome light and it's just an unrecognizable grainy mess if we look at just the caustics pass it's awful so what's happening here we've got our dome light shooting out 200 million photons but they're going everywhere the spotlight was the focused beam right on our caustics object so it's 20 million photons being emitted from this light and it we have it set going in a very restricted area here we've got it pointed our spotlight you know it's only in this area here the dome light it's going everywhere and it's the it's super inefficient and what we've got here is just I mean just a mess we can't use it so what we can do to work around this and keep our our lighting let's go back to the beauty pass here and take a look here we've got let's do another render with Alice turn these back off and take a look at our lighting and see what we've got here for our shadows do the right one okay so it looks like we've got a light source over from certainly got to a couple of shadows here a little bit harder one and a softer one larger brighter light source over on the left-hand side coming this way so it would be like maybe coming from over here we can take a look see if we've got this lined up right we want to see if the shadows going directly straight back from our camera yeah it looks like it so it looks like it's going straight back from us so we can do is take another light we're gonna do another spotlight and call this caustics all night and some movie cinema 4d tags target hunger target ok caustics only and we want to put this light up kind of where our cameras like this okay and now if we do another render here let's go ahead and leave it on this view and see we've matched up our shadows pretty close looks a little bit we move this a little bit further away and take the angle down the general under our caustics only light take this cone angle down just want to cover up where our object is we want to caustics on it okay let's go back to our main view and render we're gonna have a kind of a spotlight showing up over our scene sort of a double shadow okay exactly under our caustics only light it's going to ray we're gonna take off effects diffuse an effect specular under photon we'll turn this on take this up to two and number of photons to admit let's go yeah about ten million now well for a second let's turn these photons off we render again since we took off our ray here effects diffuse effects specular what we're getting is back to our normal HDR lit only scene so the same as we had before so that's the picture viewer so this is our beautiful beautiful scene we're super happy with it we just want to add caustics in there so now we go back to our caustics only light under photon we turn on our photon we make caustics photons render again 41 seconds so we have this 41 seconds down from let me know if we saved it or just terrible we did save it from this mess that was over two minutes now we what we have is a very sharp you know detailed caustic pattern here and it technically you know we've got we can tell by the light source out you know diffuse and softest shadow is that that's not really what we would get what we can do is take the spot light and turn it into an area light make this pretty small we don't need to be that big but area lights because of their size because the area they're shooting out all of this light in a sort of a broad pattern you will get you know no easier and more diffuse more soft caustics so we can give this a shot just to match our scene but I will probably have to tweak some settings here and probably have to up our search radius to clean this stuff but let's take a look and see what this looks like of course they did the wrong let's go back to this start over we can barely see anything so I've resized this light which decreases its output power let's go back over to Ray and do X specular thanks to fuse turn this back on and let's go back to you general and intensity multiplier do you like I don't know try 300 let's see let's do a little test render here 3000 okay so maybe 1000 1000 let's see this is affecting the scene you know another thing to which since what we're going to do is be turning off effects diffuse effects specular we don't really need decay on anymore because all we're doing all we're using this for is just to shoot photons so we can turn this on to none and that way if we move and we don't have to do a thousand this is like 120 5.01 let's try this the benefit of this is readjusting this or moving it around to change our shadow isn't going to affect the brightness once we get to styled in we don't have to tweak it anymore kind of see and get this lined up to where we want if we turn this off we can see before after seems pretty close okay all right let's go back to right and I'll turn these off now all it's doing is just firing these photons for our caustics okay and we'll turn on bucket render and take a look and see what we got yeah beautiful let's take a look here at just our caustics and see and they're not bad that looks pretty clean and that was a forty about forty nine second render slid over to the picture of you are so this is before this is with our spotlight you can see how sharp these caustics are and with this area light we've got much more realistic caustics with what our lighting would be in the scene and now this other subtle go back and look at our scene here we can see that there's another light source it's making another harder shadow over here so let's uh duplicate our spotlight our original one that we turned off control-drag we'll turn that back on and it looks kind of like this lights coming here so maybe like right like this let's take a look at our seen here and turn off our bucket render will turn this spotlight off for now so this looks like I know if you can see that in the spirit core you've got like a harder shadow a secondary light source here that's creating another shadow right here so we want to line this up straight ahead that's not coming from like right in here turn our light back on and then we'll back this up I can't slip this off I'll check whoops this off right through here we'll see how it looks like this needs to go up down a little bit spend that shadow a little bit further here we go let's turn that off it's very subtle you can take this cone angle down as well and back on okay so now I'll go to array turnoff effects diffuse effects specular over the photons and really this is subtle let's take this back down to one and maybe drop whoops just do like 1 million and intensity multiplier back down to 1 back up here and do another render so it looks like okay so I think that is just way too bright let's just point like 0.25 it's just overpowering everything you're just gonna be really subtle and try that one more time okay yeah way better so I think we've got this harder very subtle shadow here from one set of lighting from our hgri and the stronger sort of key light over from the left creating these softer caustics their object here okay so I've got this scene here so I've got a glass some went to the one in the last scene with these sort of bumps on and this half Taurus with the same sort of bumps just to throw the light through this material around the scene a little bit and this is just these two things are just sitting on a plane in the middle of nowhere with an HDR eye lighting it I've got a yarder to turn the background here and do a quick render I'll show you the HDR I it's just a outdoor sunlight HDR I take a second to prepare this scene just an outdoor bright sunny day with this update for a second there you go okay so go back to the camera so we've got this set up it's two glass objects and I have on the dome light I've got the photons turned off and I've got a spotlight zoom out a little bit here a spotlight that's covering the glass now I've turned on the spotlight I've turned off the decay so it's moving this around so much I didn't want to have to go back and readjust the intensity or anything I had that set and then now I can tweak it without having to worry about it so that is just covering this glass only and I've got another spotlight that's covering the entire Taurus and I can turn I didn't turn the decay off on this one I was able to adjust this pretty easy after I had the first one set so I'll turn on effects diffuse and okay I could do a quick render here and what I've done is just line this up to match this shadow as best as I could so I'll use this top view here as an example just like we did in the last scene trying to match the shadow of the HDR eye with the spotlight and see here so I've got the spotlight just covering this object and not this glass although it looks like I do have it just a little bit so let me tweak that I've got a target here for my spotlight and I'm gonna move this just forward a little bit whoops my target this is going to update for me quick enough there we go okay so we move this okay okay great so now I'm not getting any of this object in this light this is going to be only used to shoot photons for this this object it looks like that is pretty close so I'll stay close enough so I'm gonna go back and turn off effects diffuse so now this light is doing nothing for this scene I do have photons turned on but I'm not in bucket mode so the photons 'unity caustics won't render alright so back to this main camera scene I'm gonna go ahead and send this over to the picture viewer render out of full scene so you can see this scene with the caustics okay and like nine minutes later it's this beautiful caustics all over the place so we've got the whole object each object lit by its own light you and full caustics on the whole thing so now what if we had a scene that was a little more obstructed so if we have something like this I'm just doing a quick render here this it's a little bigger you can see we've got all of the glass that's lit but the tour is only part of it so what we want to do is have caustics on the glass like we had before but instead of all of this Taurus getting lit with the caustics light we want to just limit it to this area inside this beam of light so what we can do let's come up here and instead of using this spot light covering the whole thing I'm going to turn that off we're just gonna match up this beams I'm gonna show you here it's hot so what what I have is another spot light that's only on this area and I'll go back in and turn on let's see here affects diffuse okay so we want to adjust this a little bit just to line up with this beam of light we want to match match this right in here so this needs to be hit this whole section you what we're really focused on here is where this beam of light is hitting this Taurus so let's turn off the spotlight for a second you take a look turn our light back on you okay all right back to our light and turn off effects diffuse now if we go back here look at our photons shooting a bunch 60 million and we had the intentional intensity multiplayer cranked up to five same as it was before as soon as the other light excuse me same as this other light that was surrounding the whole thing turned it back on it's got the whole object in it but now we just want to limit it to just this little sliver and turn that off and we'll do another render here's the finished render you can see we've got just the caustics happening inside this narrow beam of light and this area here go back where the caustics were on this area they are there no more alright and so basically that's the best way to be the most efficient with firing a bunch of photons into the scene is using spotlights or very small area lights if you're trying to match diffuse or diffuse lighting but really the only way is to clean up the caustics aren't gonna be with let's go over here with the unified sampling this isn't gonna clean up the caustics there's no sampling overrides for caustics all you have is the photon number in the light and the photon caustic search radius here those are really the only things that are clean it up and this all this does is really just blur any sort of noise in your caustics that's there from lack of photons alright yeah so this is my first tutorial so if you all enjoyed this light doesn't want me to go into other topics or if there's something in here I missed feel free to leave a comment and yeah let me know what you think if there's anything I do better let me know alright thanks everybody

Channel: i_go_by_zak

Views: 29,310

Rating: 4.9872475 out of 5

Keywords: Tutorial, Redshift Tutorial, Redshift Cinema4d Tutorial, Redshift Cinema 4d Tutorial, Caustics, Render Settings, Lighting, Render, 3d

Id: ljRfI4-D6u0

Length: 50min 13sec (3013 seconds)

Published: Mon Dec 31 2018