Part1 Notes
The role of lighting TD in VFX
Responsibilities
- Assemble all the CG Assets in the shot from the upstream departments
- Design and implement lighting setup in shot to meet supervisor’s art direction
- Create production quality CGI with optimal render settings in respect to resources available
- Provide compositing team with the CG render elements required to deliver the shot
1 . Skill requirements
- Understanding real-world/ studio lighting and photography
- Knowledge in Physically-Based Rendering
- Problem-solving ( from the Pipeline point of view )
- Scripting ability ( For example: Python )
Understanding real-world lighting and photography
Help the artist to understand the motivation of the lighting design on-set and analyze the lighting methodically in order to replicate the look in CG.
- Three-Point Lighting
- Lighting Ratio
- Quality of Light Source
- Color Temperature
- Creative Setup
1.1 Three-Point Lighting
- Key light: the main source of light in the shot.
- Fill light: The light fills into the key light’s shadow area
- Rim light: For separating the subject from the background
1.2 Lighting Ratios
- Stop value is measurement unit of the exposure.
+1 stop : Doubling the amount of light
-1 stop : Halving the amount of light - The ratios of the stop value of the subject’s Key side to Fill
- For describing the lighting contrast.
High-Key lighting
- The stop difference between the subject’s Key side and Fill side is subtle.
- Low contrast ratio.
Low-Key lighting
- The stop difference between the subject’s Key side and Fill side is distinctive
- High contrast ratio
Lighting Modifiers
- Reflector is used for bouncing light into the shadow side to lower the contrast
- Flag is used to block the unwanted light on the subject to increase the contrast
1.3 Quality of Light Source
Hard light:
- Sharp transition between the Light
and Shadow on the subject. - Created by a single point of light
which is focusing on the subject. For
example: Spot light.
Soft light:
- Smooth transition between the Light and Shadow on the subject
- Created by
Large light source
Light Diffuser
Bounce light
1.4 Color Temperature
- Color contrast between different light sources helps to shape the subject.
- Interior vs Exterior
- Time in the day
Artificial lights vs Natural lights: Indicate whether it is an interior light source or from outdoors.
Natural light variation throughout the day : To suggest the time of day
1.5 Creative Lighting
Gobo lighting. Placing an object between the light source and subject in order to project it’s pattem / colour on the subject.
Identifying techniques from the plate / reference and re-create the CG lightings
Three-Point Lighting —————> Position and the direction of different light sources
High-key and Low-key Lighting —> The contrast ratio of the Key and Fill on the subject
Hard and Soft Lighting ————–> Transition from the Light area to the Shadow area
Colour Temperature ——-> Define the time and space of shot is taking place in the story
Creative Lighting ——-> Adding complexity to the lighting of the image
2 . Knowledge in Physically-Based Rendering
- Simulating light
- Behaviors of light on different material
- Method to Generate image
- Light Sources
Part2 Extension
Basic three point lighting technique
(1) Key light
Light source: It is usually the main light source in the scene. We will use it as a reference for color temperature and intensity to set other lights. If the color temperature of the main light is 5000K, when other lights are selected, the color temperature is roughly the same as that of the key light, and the intensity is lower than that of the main light.
Location: the larger the angle between the main light and the camera, the stronger the sense of volume of the main body, and the more dramatic the vision, so we have to consider how we want to feel.
Height: if we shine from below, it will create an unnatural and terrifying effect. If we raise the light 45 degrees above the main body, we have a good transition on the face and a good sense of form.
(2) Fill light
Function: the function of auxiliary light is to balance the main light and illuminate the shadow left by the main light.
Location: usually we want to put it in a complementary position with the main light, which can balance the shadow left by the main light. If you move to another location, shadows will appear in other areas.
Intensity: when we discuss the relationship between auxiliary light and main light, we are actually discussing the light ratio. When adjusting the intensity of auxiliary light, you should consider what you want to express and how you want to feel. So try to adjust the balance between the main light and the auxiliary light until you see the right effect.
(3) Rim light
Function: To separate the main body from the background, especially when the main body has dark hair, skin and clothes, and the background is also very dark, they are easy to mix together.
Location: we try to stay away from the main body in the rear. Be careful not to see the light or lamp holder in the lens. When we move to the side, be careful not to illuminate the main body’s face.
Intensity: the stronger the outline light, the stronger the sense of hierarchy, but it will look unnatural. Low intensity contour light makes it feel more natural.
(4) Background light
Function: the background light is used to illuminate the background. We use this light to control the coordination between the background and the main body.
Intensity: if the background light is turned on too much, the background will be very bright and the attention will be separated from the main body. However, if there is no background light, the background will lack vitality.
How does light play the role of “Narration” in film visual effect
Light type
1 . Direct light (hard light)
When irradiating the object, it produces clear projection and forms obvious transition layers, such as sunlight, moonlight, lightning, etc. It is often used as the main light, contour light, local modification light (eye light) and so on. It is conducive to the performance of the three-dimensional sense, contour and surface texture of the subject.
2 . Scattered light (soft light)
Only improve the general brightness of the object to be illuminated, receive light evenly, projection is not obvious, there will be no obvious light and shadow transition level. Such as skylight, astigmatism, diffuse reflectors.
Direction of light
1 . Front light
When the light source is close to the camera height and on the same horizontal plane, and the ray casting direction is consistent with the camera direction, the light is smooth, also known as front light. Front lighting can make the object receive light evenly and eliminate unnecessary shadows. Because the light of the subject is uniform, the front lighting with astigmatism makes the subject obtain soft and warm modeling effect. But usually front light is not conducive to the performance of the 3d sense of the subject, texture and sense of space, will make the picture appear flat, no ups and downs.
2. Side frontlight
The light with a 45 degree angle between the projection direction of the light source and the shooting direction of the camera is Side frontlight. When the subject is affected by the lateral smooth light, it will produce the shadow tone level of light dark transition, which is beneficial to enhance the stereoscopic sense. The scene under the Side frontlight illumination will produce projection, which can enrich the picture composition if handled properly. It is the standard light method of portrait, and uses direct light as the main light of the subject from the side.
3 . Side light
When the direction of light source is 90 degrees to the direction of camera, the light is side light. With full side lighting, the contrast between light and shade is obvious, but there is a lack of delicate shade transition.
4 . Side backlight
The light source comes from the top of the camera, and the side backlight is about 135 degrees away from the camera. The use of side backlight lighting can better outline the outline, its front dark part is larger, forming a special atmosphere, but also conducive to the performance of multi-level scenery and atmospheric perspective.
5 . Backlight
When the projection direction of the light source is 180 degrees to the direction of the camera, the light is backlight. It can delineate the outline of the scene and separate the subject from the background. It is suitable for multi-level perspective of the scene and the atmosphere, as well as the depth of space. It can also cause different effects such as silhouette and half silhouette of the scene or person.
6 . Top light
The light source projected from above the subject is the top light. The subject will form a large contrast between light and dark. When shooting close-up or close-up of a person, the eye socket will sink and the cheekbone will protrude. It is usually used to defame the person to cause abnormal feelings.
7 . Foot light
The light projected from below the subject is foot light. Such as oil lamp, fire, candle, etc.; used to render special atmosphere, such as the performance of terror, thrilling atmosphere, or in order to uglify a character. Foot light can also be used to modify light, eyes, clothes, hair, etc.
8 . Modified light
The light that can modify the shooting object is the modified light, which can partially modify the eyes, hair, face, clothing, etc. It can improve the contrast of the brightness of the picture, enrich the image level, and enhance and improve the artistic expression of modeling. Generally, small lights are used to decorate the light. It is suggested to use spotlights or area lights in 3D. Light spot, light bar and other light effects can be used to create a certain atmosphere, complete the artistic conception.
9 . Eye light
The light that makes the eyeball reflect is eye light. In general, when the angle between the main light and the auxiliary light and the camera is appropriate, the effect of eye light can be produced. If the main light and the auxiliary light can not produce eye light effect, the face lamp can be used to supplement eye light near the camera. Usually, there is only one highlight area in the eye light. Try to avoid two highlight spots in the eye, which gives people a sense of distraction.
Part3 Exercise