Computer Animation Ying Zhu Georgia State University Lighting

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

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

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.

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

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

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

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

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 http://wiki.blender.org/index.php/Manual/Hemi_Lamp

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

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

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

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

Single rig

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

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

Studio rig

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.

Standard rig

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”

Radiosity Will discuss ray tracing and radiosity later