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Time now to examine the final GI engine we will be working with in this chapter. This, of course, is the Brute force system. So with our now familiar GI room loaded, let's again run through the process of setting up V-Ray's global illumination systems. So into the Render Settings window; let's go into Indirect Illumination. I want to turn everything on. Now, by default, we get Irradiance map, and Brute force set up as our Primary, and Secondary bounce engines. As we are focusing on Brute force, let's set that in the Primary bounce slot, and let's turn off Secondary bounces for now.
Now, one thing that we do want to say right at the start: there are probably very few experienced V-Ray users who would choose to use Brute force for an interior GI solution, that is, unless there was a very specific need for it. Now, that can happen if we have lots of complex geometry; if we have very detailed geometry in the scene, then brute force may be the best option for you. It will really pull out that detail, but we have to be aware of the fact that brute force, when we are working on an interior, is at its slowest, and it is very, very difficult to clean up renders, in terms of the noise that can be found in scene.
We may want to just factor that in as we are deciding which GI engine we want to work with in a particular scene. Now, as brute force is a lot slower, in terms of render times, than all the GI engines, for this particular video, we are going to be working with some pre-rendered images. Of course, again, you can go and load these if you just go into File > Open, and come into your assets folder; here we are in Chapter 04, and you can see we have all of the renders for this chapter set up. So with our Brute force system set up, let's take a look at the parameters; the controls given to us. And you can see, we have a very, very simple set of controls. In fact, we have two; in reality we actually only have one, because this Depth option really only comes into play when Brute force is enabled to ask a Secondary bounce engine.
So to control the quality of our system, we are just working with this Subdivs parameter. With the default value of 8 set, this image we are looking at is exactly what we would get from our scene, which as you can see, is not very pretty. Indeed, lots of noise, lots of very dark areas that would need to be sorted out. Again, the first step we would take towards cleaning things up would be to turn on our Sky_Portal. So let's come up to the Window menu. Let's pull up that Outliner for ourselves, and let's select the Sky_Portal.
Close out the Outliner, and come into the Attribute Editor just to enable that light type. Coming down, we have to remember to turn on Shadows as we go, and then we want to enable our Skylight Portal option. With those changes made, we would go from this particular render, to this. As you can see, we have definitely improved the quality of scene lighting. You can see we are really pulling in a much greater level of illumination. Also, the colors are looking much more natural as well. Although there is a very high level of noise still in the scene, we can see that in areas where our geometry intersects, or comes into contact with all the pieces of geometry -- in other words, we are looking at the contact shadows -- you can see, we are getting some very nice effects indeed.
Of course, we still need to clean things up in our scene, and if we just pull up our Render Settings window again, you can see that, well, really the only option that would appear to be available to us is this Subdivs parameter. Remember, though, that the problem we have in the scene, the problem that we get with the Brute force GI system is that, well, we want to clean up the noise that is created because of the way that the system operates. So we could use our Brute force GI Subdivs parameter, or we could, indeed, work with our image sampling, and DMC sampler controls.
Well, let's do a little bit of a comparison. So first of all, let's turn our Brute force subdivisions up to a value of 24, and let's see what we would get from that. So we would go from this, to this. As we can see, it really does clean up a lot of the noise in the scene, particularly around the window opening. We can see all the noise, we see the light bounce in between these pieces of geometry; really starting to work very nicely indeed. But of course, all we would be affecting here would be the noise coming from the GI system itself. Any other effect found in our scene; any other noisy render effect would not be improved at all.
For that reason, we may want to work with our image sampling and DMC sampler approach. So let's reset our Subdivs value back to 8. Let's, instead, come into our V-Ray tab, into the Image sampler controls, and we'll leave our minimum subdivs set a value of 1, but let's set our Max subdivs to a value of 12. We are locked to our DMC sampler threshold, so let's come across to the Settings tab, and make a little bit of a tweak to that. So we are a set here at a value of 0.008. We want to make things a little bit more sensitive than that, so we are going to drop all the way down to 0.003.
With those changes made, we would go from this, to this, which, as you can see, is a very comparable render indeed. Different areas of the scene are being improved. If we keep an eye on the floor area here, you can see that the image sampling controls really clean that up, whilst this back wall actually fares better with our brute force Subdivs approach. The render times, if we look at those, are 1 minute 54 with the subdivision approach, and 1 minute 51 using the Image sampler and DMC sampler controls.
Bear in mind, though; using the Image sampler controls, and the DMC sampler settings will affect every aspect of the scene; not just the noise coming from our GI system. To finish up, then, or just to try and illuminate our scene a little bit better, let's just enable Secondary bounce engine in the system. So first of all, we'll work with the favorite, which is Light cache. Just accepting its default parameters, we would go from this, to this, which as you can see, adds an awful lot of extra illumination into the scene. And it does, to some extent, hide the noise problems that we have been seeing, just because we have that extra light bounce taking place in the environment.
Oftentimes, though, I like to use Brute force as a Secondary bounce engine as well, simply because it seems to add a greater degree of contrast, and a greater level of accuracy, in terms of the contact shadow. So let's go and set Brute force as our Secondary bounce engine. I am just going to set the Depth of the bounces -- the number of times each secondary ray can bounce -- to 5, and we would go from this, to this, which as you can see, is very comparable in terms of the illumination. I just feel that the colors we get in the scene on the contact shadows, the detail is pulled out, definitely seems a little bit better. And, of course, we would be able to work with our Image sampler controls to just clean up the noise in the scene a little bit more.
Brute force is possibly not going to be our first choice of GI Engine for our interior rendering, due to the length of render times that we can get from it. Hopefully we have seen just how easy it is to work with its very simple control set, and we've seen just how good this particular mode is at pulling out small details in a scene.
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