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Lighting and Rendering with mental ray in Maya with Eric Keller shows how to master practical mental ray techniques for rendering models created in Maya. This course walks through the most efficient and innovative mental ray techniques, including direct versus indirect lighting methods, creating different types of shadows, using the new ShadowMap camera, and reusing shadow and final gathering maps. A chapter on optimizing render times and enhancing render quality is also included. Exercise files are included with the course.
In this movie, we are going to look at some ways that we can improve the look of the indirect lighting created by Final Gathering. If we take a look at my Render view, we can see that we are getting some effect of indirect lighting, but it's very, very dim. So let's look at some ways that we can improve this. I am going to store this image and go to the Render Settings. With Final Gathering, for the most part, I only need to deal with the settings in the Final Gathering section of the Indirect Lighting tab. The first thing I can do is work with Secondary Diffuse Bounces.
What this refers to is the light enters the environment and bounces once - if I increase the number of Secondary Diffuse Bounces, I increase the number of times that the light actually bounces around the room. So I am just going to set this up to 1, and create a test render, and compare this with what we had before. Immediately, you can see that the effect becomes much more pronounced. We can see more of the room, because the light is bouncing more times around within the environment.
By just changing that one setting, we already have a brighter effect. This effect right now looks fairly blotchy. Let's look at some ways in which we can improve that aspect. The Accuracy of the default setting is of 100. I am going to increase this to 400, which is going to increase the render time but should improve the look of the overall effect. So you'll notice, as a render is being created, we are actually going through two passes.
The initial pass is where the Final Gather points are actually calculated. And you'll see that it looks very low-quality on the edges here. But that's okay. Right now, it's just calculating the Final Gather effect. Once this pass has finished, you'll see that mental ray goes through a second pass where it actually renders the room and integrates the Final Gather effect with the rest of the render. So that's the first pass. The second pass, in this case, happens very, very quickly. So you can see some of the blotchiness has been removed.
So this is before increasing Accuracy, and this is afterwards. We have increased the render time; before it was 19 seconds now it's 57 seconds. So you can see that increasing Accuracy is going to have a huge impact on your render times. The other thing that we can change is the Point Density. This is the number of Final Gather points created by each ray. Again, increasing this will improve quality, but also increase render time. Point Interpolation refers to how the Final Gather points are blended together.
Increasing this will smooth out the effects somewhat, but it can also cause a loss of detail in some of the shadowing, so it's something to be a little bit careful with. And then with the Primary Diffuse Scale, this is another way to brighten the overall effect. It's like turning the effect up. And to work with this, you can click on the color swatch and then increase these values of R, G and B. In some cases, it might be a little bit easier to switch the color chooser mode to HSV - this is Hue, Saturation, and Value - and then you can just increase the value.
So if I set this up 2 and switch back to RGB, you'll see that it's the same as setting all of these to 2. So it can save you a little bit of typing. But also I think, to me, increasing the value is a bit more intuitive. I am going to set this down to 1.1. And the Secondary Diffuse Scale has the same effect, but it controls the brightness of the secondary diffuse bounces. So I am going to increase Point Density up to 2 and create another rendering. Now we can see that we've improved the look just a little bit more.
Once again, we've increased render time significantly. Now we are up to 1 minute 31 seconds for a single frame. So it's something that you need to be aware of as you start to increase these values.
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