Congratulations! You've added fog to your scene. Now it needs lights and shadows! Here I will discuss the types of lights I used in my scene, the settings I used and how to modify them.
In this scene, I used a total of 5 lights; an ambient light which has the environment fog attached to it, 3 point lights, and 1 spot light. The simplest way to describe my light setup is if you look at one object, I have a soft highlight on the left side, and a bright highlight on the top-right side. I use the ambient light of the environment fog to act as the filler between both highlights.
The lighting set up for Cave Eggs is easily seen in the image
Here are the light settings for all my lights except ambient, which was covered earlier in the environment fog section. Take note that all my lights use a linear decay. I use decay on most of my interior or night scenes to give a softer, more natural light that dissipates the further light travels away from its source. The only time I wouldn't use decay is when the scene is in direct sunlight in an open exterior environment.
Also note, depending on the scale of your scene, the Intensity values of your lights may be higher or lower.
My light settings are shown here in the menu panels
Rendering with mental ray
There is a few different ways you can do this; you can either render in passes, or render all at once. Since this scene wasn't particularly complex, I rendered everything in 1 pass.
The image below shows what the default mental ray settings look like. I consolidated the tabs to only show things that I edited in my scene.
The default render settings menus
Many of the settings are fairly straight-forward so I will cover the five areas that had the most impact to my render and give a description of what those areas are actually doing for the environment.
: This will be a very large influence of your render time. Anti-Aliasing will alleviate the jaggedness of your polygons edges as well as affect the crispness of your textures. I chose to use Adaptive Sampling in order to save a portion of render time. Objects much further away from the camera will use fewer samples than objects closer to the camera, helping save time. In the Multi-Pixel Filtering section, I chose to use the Lanczos 4x4 setting which increased the rendering time. I chose this filter type because I wanted my textures to be as crisp as possible while still having adequate poly-edge softening. Sometimes the Lanczos filter doesn't soften the edges quite like the Mitchell filter, so I checked the Jitter box which helps correct that problem.
: This is a large portion of your indirect lighting. The best way to think about this is to go into a dark room with a flashlight and light a wall in front of you. The light will bounce from the wall and affect the surrounding area, such as the ceiling, the floor, or any object near the light's main impact area. In addition to creating this indirect light, the darkness of any shadow the light encounters will also be affected. Low accuracy values can cause splotches in your scene, most of which can be alleviated by pushing the accuracy slider up. I just pushed the slider up until those artifacts were less noticeable.
: This is a reflection of light from specular and diffuse surfaces. If you have a matte bright orange object sitting next to a white wall, some of that orange color will spill on to the wall. If you took a rounded metallic object, the reflected light will be significantly brighter and the reflected light will also be bent like the object. Caustics are very important when trying to realistically light metals and liquids. In my scene, I applied caustics so that the orange color from the cave eggs would splash slightly onto the surrounding rocks. Though, admittedly, it did very little for my scene and I could have gone without it.
: Adding this feature should definitely be coupled with Global Illumination to ensure the most realistic lighting possible. As such, your render time will increase dramatically with Final Gathering. This process essentially turns every object in the scene into its own light source. When an object in the real world is hit with light, the light hits and then bounces off that object in all possible directions. Naturally, larger values make for a better render at the expense of time.
: Ambient Occlusion fakes the darkness between 2 objects near one-another. If you place a pen on a post-it note, for example, you can see that the area where the pen and the post-it note are touching is the darkest area. That is what Ambient Occlusion attempts to accomplish. This also adds a good chunk of render time, and I have found that there is no noticeable difference in quality if your ray count exceeds the resolution of your image.
You can read more about indirect lighting in another tutorial here
Various lighting settings
And that's all folks! Thanks for reading, I hope you found this information useful and I hope to see your great work here on 3dtotal!
For more of Steven Carroll, check out his website
Another useful tutorial on indirect lighting can be found here