A Classic Technique for 3D Rendering & Presentation

Prior to the invention of artificial lights, (e.g., neon lamp & electrical lights etc), the subject of lighting and its effect has long been studied in the ancient culture, which can be dated as early as 700 BC under the field of optic study.  In fact, mankind’s interest in the properties of light does not limited to the arena of natural science, but it is also widely seen in many of our profound religious activities before it is being extended to literary works and visual arts.  For instance, in the high time of Renaissance, people did not just observed light as a natural agent that stimulates sight and provides visibility (e.g., making things visible), but it is also used to describe one’s spiritual   (or philosophical) attainment as the word enlightenment said it allSuch light up feeling can be recognised as a kind of warm emotional experience when you are leveling up or striking the eureka moment.

By making the mental connection between lighting & the idea of greater illumination, it is common for some of us to think of Da Vinci and his association with illuminati (all thanks to Dan Brown!).  Well, worry not, I am not going to discuss any conspiracy theories and its secret societies here.  However, like many other grand masters from Renaissance, Da Vinci did strive to render illumination faithfully in his works, and I think Da Vinci could be the first person who had observed and noted the phenomenon of subsurface scattering (SSS effect) that found in the organic matter, and he had applied it into his paintings (Da Vinci & Richter, 2012, pg. 118; or see the Wikipedia’s entry).  As Da Vinci wrote:

“The lights which may illuminate opaque bodies are of 4 kinds. These are: diffused light that of the atmosphere… And Direct, as that of the sun… The third is Reflected light; and there is a 4th which is that which passes through bodies, as linen or paper or the like.”

After Da Vinci, there is another highly accomplished French Baroque Painter – Georges de La Tour, who dedicated most of his lifeworks to capture the artificial lighting effect of candle fire.  La Tour has demonstrated a high level of technical mastery when capturing artificial light.  His works had made me think that he is even better than Da Vinci in this sense.  La Tour used the contrasts of candle light to achieve a sense of volume for modelling after the three-dimensionalism within a flat 2D canvas (see the following figures).  Should you are interested to learn more about the classical art that dwelled with artificial lighting, you would also appreciate the art of Giovanni Baglione too!

Lighting Study 1 - Georges La Tour Joseph the Carpenter

To our daily practice that deals with 3D computer graphics, we too are just like some of the grand old masters who is constantly working with artificial lights, except that we don’t need to crack our head for years in learning how to dap with the paintbrushes.  In fact, we are quite lucky to be able leveraging the rendering technology to emulate almost all kinds of lighting effects that to be found in the physical world and some others that running from our imagination.  Nevertheless, we still need to be observant and stayed curious like the artists of the 15th century, as the study of the nature of light is essential.

There are many different ways to emulate a system of light in 3D environment, and for the purpose of learning we are not going to talk about Mental Ray or any other physical based light engine.  Rather, I would like to “briefly” discuss our deliberate use of lighting in the context of aesthetic effect (美学用途).   By now, you all should realize that all the programmed light types that found in our 3D applications were largely borrowed from the media productions, such as theatre, video, film, and photography.  From the perspective of creative entertainment, the purpose of lighting is to create dramatic effects that can entice our audience or allure their desire to shop sometimes.  For instance, to protect their business interest, Amazon had patented their ways of photographing and lighting all their catalogued products (See below)!  Though it may sound ridiculous as it seems for owning a photographic technique that found since the invention of camera, we must aware that lighting and the use of colour does has its own psychological effects that sometimes can dent a business conversion rate.

Amazon Patented Lighting Technique

Although the Amazon’s approach looks complex as it seems, there is this simpler lighting method that known as the Three (3) Point Light, which can be cross-applied into all kind of visual productions including computer-generated imagery (CGI).  As the name implied, the method of 3 Point Light uses lights that set in three different positions to illuminate the subject (such as a person or 3D Model).  The only fun and unique thing in 3D lighting is that we can control which light to cast shadow or absorbing other lights intensity with negative value!  In real world, you can’t do so with a real lighting kit.  To setup three point light in a 3D scene, we always starting off with a bright key light, and follow by the fill light and back light.  Below is a functional summary about these three (3) types of lights:

Key Light

As the name connote, key light is the main illuminator for the entire scene.  It should command the highest value of intensity while tying up with the prime colour key.  Also, it should be the only light that is shadow-enabled.

Fill Light

The purpose of fill light is to cover a subject’s unlighted surface that missed by a key light.  It usually acted as a softener to eliminating the stark contrast and shadow that caused by a key light.  Therefore, it usually has much lower intensity with a complementary colour key for balancing the composition.

Back Light

The back light is often being placed in counter direction of the key light, and it is known as the rim light as well.  The purpose of a back light is to enhance the silhouette of a subject, by providing a rim of light that outlined the subject’s edge.  This will help to separate the subject from the background and subsequently increasing its visual interest to the audiences.  Back light is also commonly used to provide some shines for the hair and the shoulder of a character during staging.

3 Point Light Setup for 3D Model

 

Setting up a 3 Point-Light

As mentioned before, in order to compose an effective 3 Point-Light effect, the positioning for each of the light types is very important.  I would strongly courage you to follow the suggested arrangement from the above diagram as a start before you tweaking it to suite your needs.  Do keep in mind that the orientation and the position of the key light had to be parallel with the render view of the camera.  Remember, the render view is also your audiences viewing perspective as well.

In contrast, the back light needs to be directed from the opposite view of the camera.  You can explore the options for positioning the back light within the suggested area.  Alternately, you can add an extra back light and change the entire composition to the “4 Point Light” setting, so that the subject has the optimum light rim effect.  As for the fill light, you can choose to either place it on the right or the left-hand side of your model; it is entirely subjected to structure and meaning of your composition that you would like to present. (you can read more about it in cinematography).

The workflow for setting up a 3 Point-Light in 3D environment is actually quite straightforward, as the positioning of the lights are all depended to the camera’s render view.  In fact, you need to nail down the framing of your composition first before setting up the light, and always remember to lock your 3D camera after you have decided on its viewing angle, aspect ratios and pixel resolution (e.g., HD720 in the render settings etc).  As long the positioning of the 3D camera is set, you can begin to light your model with a key light that is shadow enabled, then follow by the fill light and back light as demonstrated in below.  Alternately, you can add a fourth light (aka the kicker light) at the near end of the process for softening the entire composition.  To do so, I would use a low intensity point light (or Omni Light in 3dsMAX) to give it an extra kick.

lightingSequence_gameartworkbook

Case Studies

The process of setting up a 3 Point Light in 3D Rendering can be easily mastered as long you know how to control the total intensity of all the lights that found in your scene.  Heuristically speaking, I would not use more than the total value of 3 with all the combining intensity-value for my lights.  In fact, I would distribute the intensity for each of the lights with these two variables in mind: the total number of lights in the scene and its level of importance in relation to the model, as demonstrated below.

Scenario 1
Lights Key Light Fill Light Backlight Total Intensity
Intensity

1

.5

1.5

3

 

Scenario 2
Lights Key Light Fill Light  Backlight Kicker Light (optional) Total Intensity
Intensity

1

.4 1.35 .25

3

 

The rationale behind this sort of rule of thumb is meant for attaining a balanced exposure when lighting your 3D model.  For instance, let’s look at the following Sample 1.

Sample 1

3 Three Point Lights Sample Case Study 1

Sample 1 is a good work-in-progress (wip) example that carried the visual evidence of bad exposure (over-expose).

1. As pointed out in (1), all the textured-details for this lighted area has been washed away by the immense intensity of the key light!  At max, the intensity for this key light shouldn’t be more than the value of 1.5 even if you want to emulate a broad daylight.  With such overly expose imagery, your audience (me) will not be able to see all the normal and specular map effects that you have planted.  Besides that, the key light had cancelled the effect of the fill light too.  Lastly, the orientation of the key light needs to be tilted down more for avoiding an elongated shadow.

2. Secondly, the base of the turntable deserved better polygonal-resolution.  For the purpose of presentation, it isn’t a good idea to complement your game model with such a low edgy-looking cylindrical chunk.  I would advise you to increase the resolution of the turntable, and not to worry about the polygon count when you bevel it, as demonstrated in the following example.  Also, do try to size the turntable with some reasonable radius, so that the shadow of your model can be better captured.

Sample of Turntable Base Mesh

Should this turntable render of yours is going to be a showpiece in the demo reel, then I would strongly encourage you to “decorate” it with more polygons and textures, as what the pros has demonstrated in their works.  However, do not overly doing it too, for you do not want the turntable stealing the limelight of your character work.

Turntable_examples

3. Thirdly, the blue-colored back light failed to give the rim light effect over the character mesh.  This is simply because the back light did not set in accordance to the camera’s viewing angle.  Besides that, the angle of the back light has been tilted down in way too much.  Remember, you should focus on lighting the game character and not so much of the turntable.

Sample 2

3 Three Point Lights Sample Case Study 2

The above Sample 2 is another interesting wip example; overall, it had near balanced exposure with a working back lighting effect.  This had made the entire composition to have much better legibility, as all the bodily textures and details can be clearly seen.  Notably, the used of a grey-colored background does have its effect too for it had help to us to focus more on that “green-thing” instead of others.  To do so, simply go to the attributes editor of your render camera (renderCAM), then lookout for the Environment dropdown menu and tweak the Background Color from there.

Although Sample 2 fares much better in term of lighting & rendering if compare to Sample 1, nevertheless it still has a poor looking turntable that plagued with normal shading issue (See 1).  Also, the orientation for key light needs to be re-adjusted for removing the elongated shadow.

Summary

The method of 3 Point-Light is actually quite easy to learn and apply.  Besides that, it is also quite cost effective during the process of batch rendering as it uses less rendering time if compare to other rendering approaches (like mental ray).  Although it is arguably that the method of 3 Point-Light in 3D rendering is seemingly limited if we want to generate a hyper-realistic render, nevertheless the method itself can be served as a good starting point for you to build the required complexities at later stage.

I hope this article will provide you an additional insight when composing your turntable render.  In sum, never underestimate the importance of lighting during presentation.

#End.


References

Da Vinci, L. & Richter, J.P. (2012). The Notebooks of Leonardo da Vinci, Vol. 1: 001 (Dover Fine Art, History of Art). Dover Publications: Kindle Version.