1. Computer Graphics Imaging Ying Zhu Georgia State University
Lighting

2. Color
In previous lectures, we have learned how to change the location, shape, and size of an 3D object.
Now we are going to learn to add color to an object.
In computer graphics, you generally do not “paint” color directly on the surface of the object
The color of an object is calculated based a lighting equation

3. Color
To change color, you set up lights, manipulate surface material properties, and apply textures
In general, follow this order
Set up lights
Set surface material properties
Apply texture

4. Lighting Parameters Things you can control in Blender: Type of light
Color of the light
Position of the light and it’s direction
Other parameters: e.g. energy, dropoff, etc.

5. Types of lights To add a light, press Space bar, and select Lamp
Five types of lights
Lamp
Area
Spot
Sun
Hemi

6. Lamp light In Shading panel (F5), click Lamp Buttons icon
Parameters you can control
Dist(ance)
Energy
Color
Fall off
Shadow color, etc.

7. Spotlight Parameters you can control Dist(ance) Energy Color Falloff
Spot light angle
Spot light edge
Halo (volumetric spotlight)
Texture
to simulate a projector

8. Area light Simulate light emitted from an area, not a point
TV screen, window, or cloudy sky
Create soft shadows
Parameters you can control
Dist
Energy
Color
Shape of the light

9. Hemi light Simulate light emitted from a 180 degree hemisphere
E.g. heavily clouded sky
Has no location, just direction
Simulate outdoor light
Use a warm yellow Sun light and a weaker bluish Hemi light
For details see User’s Manual

10. Sun light Simulate sunlight Parameters you can control
No location, just direction
Cannot adjust intensity falloff curve
Parameters you can control
Dist
Energy
Color

11. Lighting rigs Standard setup of lights
Very important for creating a particular mood
Often overlooked in previous CGI course projects
Note the default camera location in most lighting rigs
15 degrees off dead-on
25 BU back
9 BU to the side of the subject
Eye level

12. Ambient only Under Shading panel (F5), click on “World buttons” icon
Can change AmbR, AmbG, AmbB to adjust the global ambient light
An rough simulation of the lights reflected from surrounding objects (e.g. walls, clouds, etc.)
Does not create shadows
Can be used to lighten up the scene a little

13. Single rig
Provides a dramatic and showy illumination of one or a few objects
Direct the attention to that object
A spotlight is placed above and directly in front of the subject
10 BU in front and 10 BU high

14. Single rig

15. Two point rig Provides a balanced illumination of an object
E.g. light a glossy product
Two hemi lights

16. Studio rig Use three lights Provide both soft light and highlight
One area light (key light) slightly above and to the left of the camera
Two hemi lights placed at the side and in front of the subject
Provide both soft light and highlight
Can be used to film a talking actor or highlight one actor among several

17. Studio rig

18. Standard rig
Similar to the studio rig but move one side light behind the subject (a backlight)
The key light is now a spotlight
Can be used in 3D animations to light the main actor
Use this rig especially if you have transparent objects (like glass) so that there is plenty of light to shine through them to the camera.

19. Standard rig

20. Volumetric spotlight Only available for the spotlight type Steps
Select the light
In the Shading (F5) panel, select Spotlight
Under Shadow and Spot, press the Halo button
To cast shadow in the light shaft
Press “Buf(fer) Shadow” button
Increase “Halo step”

21. Radiosity
Will discuss ray tracing and radiosity later