Our thanks to Reynante Martinez for this tutorial. For more of his excellent work, head to www.reynantemartinez.com.
This tutorial first appeared in issue 83 of 3D Artist.
Lighting, in its broadest sense, can make or break a scene – it is often one of the most overlooked aspects of 3D and will dictate how believable and captivating your scene will be.
This is also one of the primary reasons why some artists will dedicate their 3D career to understanding and deconstructing it.
And with the advent of the Cycles rendering engine for Blender, lighting has never been so fun and intuitive. With that said, there are a few basic principles and rules to follow to create and complement convincing imagery, which will also give you more room to break these and experiment.
The question of what type of lighting is best comes up often. As much as we would like to give a definitive answer to this, it all depends on what scene you currently have and what emotion you are trying to portray. It also goes hand in hand with the other aspects of your scene and should, in most cases, exaggerate and give more meaning to them.
A very rudimentary example of this is when you have gone all the way in creating a very detailed model that has very convincing and realistic textures applied to it; however, during the lighting stage, you decided not to give much emphasis to it and just dropped in a few lamps here and there.
After a while, you realise your scene isn’t looking as good as you had hoped it would be, despite your efforts of adding all the necessary modelling and texturing details. Disappointed, you decide to abandon the project and swear to never finish it.
In this brief guide, we’ll touch on the fundamentals of lighting and how you can incorporate them into your scene and avoid caveats that may demotivate you.
Step 01 – Basic scene setup
For this guide, we will be utilising a very basic scene setup: a sphere and a backdrop. This is most useful when gauging your lighting scheme and will serve as a great reference later on when attempting larger and more complex scenes. Add a UV Sphere with the default settings, add a Subsurf Modifier level 2, and set the shading to Smooth. For the backdrop, add a Plane with a Subsurf Modifier level 3, then extrude the back part, as seen in the image below. Next, place your camera in front of the sphere so you can clearly visualise the whole scene.
Step 02 – Material and shader setup
In the meantime, we won’t be using any fancy materials and textures, just so you can clearly absorb the idea and not get distracted by other prevailing elements. Add a grey (RGB = 0.5) Diffuse material to the sphere and backdrop. You can either use the Properties Editor or the Material Node Editor when adding materials to an object, the latter providing you with more control over the nodes as needed. At this point, make sure you have the Cycles render selected as the scene’s renderer.
Step 03 – Key lighting setup
In the following steps, we’ll gradually build a lighting setup that is most commonly used in photography studios and product visualisations. The key light serves as the primary source of light in your scene. Its purposes include (but are not limited to) the following: highlighting/emphasising the main subject, providing the initial shape and adding the main shadow. Add a Sun Lamp, position it at an approximately 45-degree angle (Top View and Front View). Reduce the size to create sharper shadows and use a relatively higher lamp strength than the default value.
Step 04 – Fill lighting setup
The fill light is used to add illumination to the unlit portions of your subject and to even out the shading. Usually, in photography studios, they use a softbox – a type of modifier that scatters and softens the light shot from a strobe or flash. In most 3D applications, we can replicate this by creating an object that will emit light.
In Blender, add a Plane, position it adjacent to the Sun Lamp but on the opposite side of the sphere, scale it to a relatively large size, and add an Emission shader to it, increasing the strength as needed. You’ll now notice that it killed the dark shading that we previously had, as well as adding a soft shadow opposite the emitter’s location.
Step 05 – Back lighting setup
As you may have already noticed, this completes the three-point lighting setup. This type of lighting is a cliché to artists, however, it serves its purpose well and lives up to its reputation too. Used sparingly, these lights will give life to your scenes that you would never have achieved otherwise. The back light, or rim light, is used to add definition to the overall shape and silhouette of the subject. When used on character portraits, it creates this wonderful scattering effect that is most noticeable on the hair strands and on skin. Add a Sun Lamp in Blender, position it opposite the key Light or the fill Light, and adjust the strength accordingly. Depending on your scene setup, you also may want to create another back light to compensate the other side of your model, as well as disabling the shadows being cast from these light sources.
Step 06 – Ambient lighting setup
The primary purpose of ambient light is to simulate the illumination that we receive from the sky, for example, on a cloudy and overcast day. When used alongside a CG and live action composite, this can help blend the CG scene seamlessly with real-life footage. Blender doesn’t have an explicit way of achieving GI (global illumination), but by adjusting the World’s settings, the results are almost convincingly similar. You can use this technique in conjunction with the key light method, but a better option is available on the next step.
Step 07 – Image-based lighting (IBL)
One of the reasons we use HDRIs is because they have a higher bit-depth and can store additional lighting information that can dictate how your scene will be illuminated based on the image’s light intensity values. This technique is often used by animation studios worldwide to give more life to their scenes as well as seamlessly blend several elements together (ie by shooting a panoramic HDR of the set). In Blender, you can do this by adding an Environment Texture and adjusting the strength accordingly.
Step 08 – Image-based lighting controller
With the setup as seen in Step 7, we can further control how the lighting behaves by adding a couple of nodes in Blender that will enable us to rotate the environment texture, control the light intensity, control the light fill and adjust how much reflection it casts on reflective materials and objects. For the purposes of illustration, we’ve added two reflective (metal and dielectric) objects. However, there are still a lot of possibilities with IBL in Blender and we are only touching the surface with this tutorial.
Step 09 – Volumetric lighting setup
And to conclude this brief overview to lighting, we’ll introduce you to one of Blender and Cycles’ new features. Volumetric lighting simulates situations which include fog, god rays, dust particles and the like. To achieve this in Blender, simply attach a Volume Scatter node into the World Output node’s Volume Input, using a Spot Lamp as the primary source of light. By default, volumetric rendering in Blender is relatively slow, however, there are a few tricks to work around this with little or no detriment to quality.