Join Brian Bradley for an in-depth discussion in this video Working with irradiance mapping, part 2, part of SketchUp: Rendering with V-Ray 3.
- [Instructor] Although we have made a good start at getting a decent GI solution from the irradiance mapping engine, we would have to admit that we're still quite a way short of having a nice, clean solution and render. We still have some very obvious splotching coming from the irradiance mapping itself and you will also have noticed that with the addition of the sky portals, we have actually introduced quite a bit of fine noise or grain to the image. To deal with the first of those problems, the splotchiness, we could increase the resolution of our irradiance map here as we are still only making use of the low to medium settings that V-Ray gives us by default.
The problem with increasing irradiance map resolution though is that we can sometimes add significantly to overall render times without necessarily making any significant difference to the splotching that we are seeing. Sometimes a better approach is to try and work with two of the other parameters that we have here, namely subdivs or subdivisions and interpolation, often referred to as hemispherical subdivisions and interpolation samples in other versions of V-Ray. The subdivs parameter controls how may rays are traced from each of the irradiance sample points that V-Ray has placed in the scene, whilst the interpolation option determines how many of those irradiance samples are averaged or blended together at final render time.
Let's do a quick test using each of these controls. First of all, after making sure that our current render is added to the history list, let's bump our interpolation to quite a high value, say something around about 100 and again, take a render. The final result if we compare it to our previous image shows that we have indeed cleaned things up or more accurately smoothed them out somewhat. We did say though that we could also work with our subdivision control and so, with our interpolation value reset to 30, let's bump the subdivs up to a pretty high value of 200, save what we have to the history list and again take another render.
Now, whilst our render time does increase dramatically which isn't surprising given that we are theoretically now calculating a much better lighting solution and given that the more rays we use, the more accurate our lighting should be, a quick comparison between the two images reveals that this particular parameter change hasn't made any appreciable difference to our problems at all. That being the case then, let's drop our hemispherical subdivs back down to a lower and so faster to calculate value of 75.
Let's also set our interpolation up a little bit at 50 and then move on to tackling the fine noise or grain that was added when we enabled our sky portals. Now, before we try to clean this up using any kind of brute force sampling, we do need to understand that the irradiance map engine only adds a single bounce of light to a scene which of course is not how light behaves in the real world and this is a real contributing factor to all of the problems that we are seeing here.
To mimic real-world light behavior then, and to help bring our GI solution up to an acceptable level, we really do need to enable one of V-Ray's secondary bounce engines and in an interior setting such as this, the preferred option for most experienced users would probably still be the light cache system. Let's go ahead and enable that and after leaving all of the light cache settings at their defaults, take another render. What we get now shows quite a difference in terms of illumination levels in the scene which of course in turn also helps with the splotching and noise problems that we have been experiencing.
An added bonus here is the fact that we have actually decreased our render times by quite a bit. To add a couple of final tweaks that can help improve our render even more then, let's increase the resolution of the irradiance map just a little bit by setting the min sample's value to minus two and the max to one. We can increase our light cache subdivs to a value of 2,000 and then after enabling the ambient occlusion feature, take a final render. Having looked at some of the basic controls found in the irradiance mapping system then, let's move on in our next exercise and take a closer look at the other engine that we made use of here, this being the light cache system.
- Gamma handling in V-Ray 3 for SketchUp
- Working with interactive rendering
- V-Ray light types
- Working with irradiance mapping
- Rendering animations
- Working with the V-Ray camera
- Using the Materials UI
- V-Ray FX tools
- Stereoscopic 3D rendering
- Using V-Ray objects