Make Your 3D Lighting Shine - Tips for Realistic Lighting
Lighting is a critical part of the rendering process. The goals for 3D lighting are the same as in the real world; you need to properly illuminate your scene or subject in the best possible way. If you were to look at a photographer or cinematographer, you'd notice they don't just use the lighting that is given to them in that particular room or area. Instead they must recreate light and light direction in order to produce the best possible results. You're essentially doing the same thing, but you are using a 3D light setup for your 3D scene, and it doesn't hurt to have some helpful tips for establishing more realistic 3D lighting.
If you don't have good lighting for your scene, then your renders won't produce the results you want. Trying to simulate real-world lighting in a computer-generated world can be a daunting task. However, if you apply some simple lighting techniques and workflows, you can ensure the lighting for your scene will match the mood and emotion you're trying to get across to your audience.
You're working in 3D space, but what is rendered and displayed on the monitor is still a 2D image so lighting plays a critical role in establishing the correct shadows and highlights to give your render that three-dimensional look. All 3D applications provide powerful lighting capabilities that can simulate just about any lighting desired; you just need to know the basic practices to get to where you want to be.
Use Global Illumination
In order to achieve photorealistic lighting results, your best best is to use global illumination (GI). Take the time to understand Global Illumination, if you don't already. Global illumination simulates how light interacts in the real world by carrying different color values and distributing the light evenly based on what the light rays come into contact with. It can greatly increase render time but it's also vital for establishing more photorealistic results.
Outdoor Environments Don't Need a Lot of Light
If you're working with an outdoor 3D scene, the lighting needed to create photorealistic results is often a lot simpler than you may think. It's a common mistake to have way too many lights in an outdoor shot when, in reality, all that's needed is just one or two. In the real world when someone is outside during the day the obvious point of illumination is direct sunlight and the sky. The direction that the sun is shining determines what time of day it is.
You can achieve this by using a simple directional light, with adjusted intensity, direction, color, etc, to achieve the look that you want. You can also add in a type of sky dome to simulate the light and shadows that would be cast from the sky. This is a very simple but effective way to achieve a photorealistic light setup for your outdoor renders. You can use global illumination in conjunction with this type of setup to achieve an even better result.
Render Lighting Elements Separately
There is inevitably going to be some adjusting that needs to be done later on in the compositing stage, whether it's color balance, light balance or specularity. So it's a good idea to render out separate lighting passes so you can adjust things after the fact. You can also breakdown the scene to see exactly what type of effect each pass is having on the final render, and how to fix an area that may not look right. For instance, you can turn off the diffuse pass or separate lights to see if they have an added benefit to your final composite. This will let you see what isn't really needed, and also what you might need to add.
Light Direction & Color
The direction of the light source can enhance the shape of the subject and, depending on the direction of the light, it can give off a completely different feeling for your shot. You should be thinking about where you want the direction of the light to come. For example, if this is a night scene outdoors the light source will be from the moonlight or maybe from a street lamp.
Along with light direction, the color for your light is also key for simulating realistic lighting. For instance, very rarely will a light give off a completely white color; more often it has a yellowish tint. You can also use color to enhance the temperature for your render, maybe it's a very warm and sunny day so there is a more prominent yellow tint to the light or, if the light is coming from the moon, it might give off a blue hue.
Preview Your Lighting in the Viewport
Most 3D applications by default won't display the light source in your viewport. You can move it around and change the direction, but you won't see the effect it has on your scene until you actually render it. Having to render every time you want to see your lighting effects can be quite time consuming. If you use something like Viewport 2.0 in Maya though, you can see exactly what type of effect the light is having on your scene, including color and intensity settings, without having to render, and saving a lot of time in the process.
Use Reference Material
As with any other task within the pipeline, reference material is one of the best ways to achieve realistic and believable results. Even if you think you know how the light should look, without comparing to real-world examples, you could be missing out on the small details that could really make your render look absolutely real.
If you're lighting an outdoor scene, grab some outdoor photographs, either from the internet or just take them yourself, pick the time of day that you are trying to replicate, and compare them closely to your render. Study how the light is being reflected, how the shadows are being cast, and the light direction and intensity the light source is providing. This comparison will give you a better understanding of how your final render should look, and what needs to be adjusted to get the most photo realistic results.
Next time you're tasked with the challenge of creating photorealistic lighting, try incorporating some of these tips into your workflow. Experiment with different light types and different settings to achieve the desired results. If you aren't sure how your lighting should look, find some reference images to help you establish more accurate results.
If you want to learn more about realistic lighting, check these 3D lighting tutorials: Rendering Interiors with V-Ray for Maya, Creating Interior Visualizations in 3ds Max and an Introduction to Lighting in CINEMA 4D.