Cycles Max Bounces | Blender Light Paths Render Settings

if you have a look under your render properties tab you'll see a section for light paths specifically max bounces now what is that and how does that actually affect your renders in this scene we have a ball right here which is given just an emissive material and it's inside of a room with a partition dividing it from this section over here so if we take a look at the rendered view right now i have the total max bounces set to zero so what that means is all of the light that is being cast from this ball is hitting whatever surface it comes into contact with and stopping there it's not bouncing around and say going over here bouncing hitting the floor or anything like that it's just hitting a surface and stopping as a result the second partition over here this little room is completely black because no no light can directly go from here into this section and since it's not bouncing it's not able to say hit the floor and bounce back this way either so we can increase the total bounces and suddenly you can start see getting a little bit of detail in here and this is just with one total bounce so that means light may be going over here and then hitting this wall over here and then it's stopping it's not bouncing and hitting that wall maybe it's coming over here it's hitting this wall over here then bouncing off into that wall if we increase it further we get progressively more light it's hard to tell with all of the noise that naturally comes with a cycles render but it it does get a little bit more if we can let's actually right now let's take this right here if we go into the camera view you can see if we take it all the way down to zero bounces here we are again it looks black increase it to one bounce you get a little bit of light there so let's actually take that and do a real quick render all right so i finished rendering a few different versions of this this is the one we just did with one max bounce allowed and then if we bump it up to two max bounces you can see it gets a little bit brighter over here and actually this this side of it also gets brighter and then we bump it up to five more bright as well it's starting to get a little bit noisy but as you can see it does allow for increased brightness because what happens in the real world you're not going to have a limited number of bounces like this you're not going to get just five bounces what's going to happen in the real world is it's going to bounce and it's essentially just going to keep going in whatever direction the light takes it until it eventually reflects so much that it loses all energy and does turn into black but computers cannot do an infinite number of calculations so as blender artists we have to choose what level of realism we're willing to go for because going from one one max bounce you see it has a render time of eight seconds each time you increase it you increase from one to two it more than double it pretty much doubles go from two to five it increases a little bit more at that point we're getting more into the noise threshold side of deter limiting factors here but point being the more you increase the number of bounces the longer your renders are going to take but the more realistic it is and that like always it's always a trade-off between true photo realism and uh good good rendering times so that leaves us with whatever these other sections are we have diffuse glossy transmission and volume alright so these next five sections are essentially limits on specific types of light bounces and this could be very useful depending on the type of scene you have if you have a scene with a lot of glossy surfaces in their reflective surfaces you may be able to play a little bit with that value and get a better rendering performance and not sacrifice a whole lot on photo realism same goes for diffuse transmission volume and transparent most of the time you can leave these settings as is but let's just take a look at how they actually affect what you're doing so here we have the exact same scenario but the room is just a diffuse bsdf i switched it from the principal bsdf to just diffuse so let's take a look at how that affects what we're doing so if we take it down to zero total bounces we end up with the same situation it's all well lit on one side and completely black on the other we take it up to one it's the same result as we had before you know this this right here it's the same but then if we actually start increasing the total bounces right now since our diffuse is set to one what you're going to notice is that no matter how many times we increase this no matter what value it is it's going to look exactly the same and that's because the only type of bounces that are happening in this particular scene right now are diffuse bounces since our little room is made out of a diffuse bsdf so the only way to actually get more bounces is by increasing it on the diffuse specifically so in other words between these two in this particular scenario it's going to be whichever one of these is lowest is going to be the limiting factor because after all if we increase this back to its default value of 4 and take it down to 0 it's still going to follow the same behavior as we had before so it's going to be whichever one of these is lowest is going to give you your limiting factor and determine what gives you the most realism so then we can take a look at the glossy we switch this over here to a glossy bsdf first of all that's really rough so let's change that just make it a little bit you know rougher like that a little bit you can still see how it behaves as a glossy surface when we have it like that let's take it all the way down to zero what do we got total total bounces are zero so whatever you see it's gonna go from this ball right here it's gonna hit the surface and bounce off directly into the camera a glossy surface is a lot more reflective if we increase the total from zero to one we're starting to get some of that behavior where it's lighting up this section of the of the room we're getting a little bit of lighting in there increase to two and so on and so forth we get there and we can go backwards going uh limiting from the glossy side specifically and we're getting that initial same behavior there as we did before all right so here we are back looking at volume what have we got here still got that same initial room set up with the ball inside the little room this time though we've got this big cube surrounding the entire room and right now it's set with a volume principled volume uh shader so what does that mean well let's look at it from here right now you can see the outline of our cube and the ball inside there is shining light out into the cube if we take a look at the volume shader or the volume bounces specifically it's set to zero so what does that mean uh basically the light is going in there and however far it gets that's the power of it and that's essentially that's what you're seeing if we increase that by one click you can see it starts spreading a little bit more it's a little bit more diffuse you're getting some more complex interactions with the scene go down from there and as you do that each time you can see your start starting to get a little bit more specs everywhere within the volume honestly leave it at zero unless you're running you know ultra realistic because that increases your render times a lot and it for very minimal advantage uh in fact i will render a couple of shots with different max bounces and we'll take a look at that in just a second alright so i've rendered out a few different versions of this with different settings on the volume bounces so here's with the default of zero bounces you know you can get that uh volumetric look here going pretty good if you increase from zero to one you actually you know it does spread it out a little bit more but you actually go from a render time of 111 to 141 which is not great if you increase from one to three you get a little bit more of that on there not as dramatic an increase as from zero to one uh render time does go up by about 14 seconds though so again i would personally recommend just leaving this at the default unless you did need a specific look you were going for like in this case you know we can see the if you have just zero you can't really see this second compartment in there if you increase it to just one you can start to see a little bit of detail going on inside there and if that's important to you then by all means increase that uh otherwise just leave it as is all right so if you want to take a look at the transparent light bounces let's take a look at this scene right here we have three planes and one light and these two planes right here are both given this transparent shader whereas this other plane right here is just given a regular bsdf shader right now the light paths are set to too transparent so the light cont it still gets through if we increase it further no matter what we increase it to this plane over here is still illuminated by the light over here when it's going through both of these right here it goes through there through that one and then eventually onto that plane and as long as this number is sufficiently high it doesn't matter what it is the plane will be eliminated if we go all the way down though you can see that it actually with zero transparent bounces it is not illuminated at all so what does that mean for us well it essentially means that the light is going and hitting this one and stopping and that is the end of that story if we increase it to one we get some weird funkiness that i don't really understand why why it looks like that uh we can you know move that up if we move the one plane away so that the light essentially is just passing straight uh into the one plane then no issues there it's only whenever we start having a little bit of interaction between everything even then it's not it's not there i don't know anyways uh the thing though is it goes both ways the transparent max bounces and what do i mean by that essentially the light with one you know we can give it two transparent bounces so the light is able to go through here through that one and hit that and then it can come back towards us so we can see the plane but if you'll notice if we have a single light bounce what it cannot do is pass back through here through the plane and to us so the plane essentially acts as a holdout it cuts off the light you can't see behind it if you increase it a little bit more then what you've got here is you can see through a single transparent plane you can see through it um but what you cannot see is when it has to pass through two planes so if we switch back over to solid view mode this cross section right here the light has to pass through both planes back to the camera in order for us to see but since we only have two light uh bounces available for transparency it continues to act as a holdout but if we increase it yet once more we suddenly can see again however yet again if we increase this if we have instead three planes that it has to go through i can if we have three planes that it has to go through then yet again we cannot see behind that since we're only at three so yeah that's just kind of a basic introduction into the light paths just figure out what works for you and what settings you have most of the time the default values are fine they give you reasonably good performance and pretty good realism i wouldn't change them unless you're doing like an animation or something that requires you to have or squeeze as many seconds out of your renders as you can otherwise leave it all the same and i'll see you on the next video

Channel: Learn Together Filmmaking

Views: 18,419

Keywords: blender, tutorial, cycles, settings, render

Id: L2uYyoPwk10

Length: 14min 17sec (857 seconds)

Published: Mon Mar 07 2022