Learn how to optimize Diffuse reflection depth.
- [Instructor] Our simple triangle lighting setup is ready for fine tuning. Let's take another look at the physical camera rendering. Click on active shade on the main toolbar. And we have a pretty good result here, but most of the illumination in the fill area is being provided by this fill light, and we're not actually getting a very good global illumination in this particular shot. That's because the default number of diffuse bounces is only one.
That means when a ray of light hits a surface such as the table cloth. That light will bounce off the table cloth, and hit another nearby surface, but that's the end of the bounces. With only one diffuse bounce, we're not getting a very good GI solution. So let's improve that. Go into the render setup dialogue, and in the Arnold Renderer tab we have the diffuse section, and by default we've got two diffuse samples, and only one diffuse ray.
We can increase this value up, and that's going to brighten the shot, but unfortunately we won't see that in the active shade window. We'll need to re-render. Every time we change any of these parameters, we'll need to refresh the active shade. Let's bring the number of diffuse rays up to six. And click the render button. We see that immediately it's a lot brighter, and if we let this finish we would also see that the quality is better because as we increase the number of rays, we're increasing the overall number of calculations, and that will reduce the amount of grain overall.
Well I know that this is over exposed at this point, so I can make some adjustments to my lights. I'll select the backlight over here, do that in the front view port. That's the backlight, and then go into the modify panel, scroll down and reduce the exposure. Let's bring the fill light exposure down to a value of six. And now we're getting better contrast. And likewise with the light coming from the other window, and that's the backlight.
Let's select that. We can navigate in the view port with middle mouse, and the mouse wheel dolly back. Here's our big backlight out there so we can select that, and then in its modify panel, set the backlight's exposure to negative two. And now we got a pretty good lighting solution here. And if we let this finish it will look okay in terms of the overall lighting, but it will still be a bit grainy.
So we want to switch over now into production mode. I'll close out of the active shade window. And in the render setup, set the target to production rendering mode. Go to the common tab, I want to render a smaller frame so click on 640 by 360. And then back to the Arnold Renderer tab. Notice that the ray depth has set itself to one, and that's because the settings for production rendering and activate shade are separate.
Let's increase the number of diffuse rays to six, like we just saw. And also increase the overall anti-aliasing to reduce the amount of grain. Set the camera anti-aliasing up to six also. Go ahead and click render, and that'll take a little while. We'll check in on that rendering once it's complete. We can see in the production render that it's still a bit grainy. So we've got quite a bit of noise especially in the shadows.
Let's make a copy of this so that we can compare it. Click on clone rendered frame window. Keep that off to the side. And to improve the quality of the rendering we might be tempted to adjust the camera anti-aliasing. We've got that at a value of six now, and if we increase that value we would get rid of a lot of this noise. However, there's a little bit more efficient way to do it. Because the noise is really the result of the diffuse reflections, we can increase the number of samples for the diffuse component only.
And that way later when we start adding reflected materials and so on, that doesn't get over sampled. In other words, if we increase the camera anti-aliasing up to like 10 or something like that. Then that would multiply the number of samples for the specular transmission subsurface scattering and so on. But we may not need to do that, we really only need better quality in the diffuse reflections. So let's only adjust the diffuse samples. Bring that up to a value of six also.
And then do another render. And be prepared for a longer wait this time because we're calculating quite a lot more samples. Our render finally completed, it took quite a lot longer due to our high sample values, but we needed those high samples in order to mostly remove the grain. The grain is especially visible in this shot because we have no textures, and it's just a flat white diffuse material.
Let's position the before and after images side by side. On the left we have six samples for the diffuse component, and on the right only two samples for the diffuse. Our triangle lighting setup is complete, and that concludes the chapter on studio lighting.
- Arnold rendering concepts
- Arnold lights such as quad, spot, and distant
- Modifying Arnold object properties
- Filtering light with the gobo filter modifier
- Image-based lighting with Skydome
- Daylight simulation with Physical Sky
- Arnold Standard Surface material parameters
- Diffuse, opacity, and bump mapping
- Rendering refractions with Transmission
- Building an Arnold shading network
- Test rendering with utility map
- Mesh subdivision and displacement at render time
- Atmospheric perspective with scene environment fog
- Rendering a spherical environment with VR Camera