Shading - Computer Graphics - Lecture Notes | ECS 175, Study notes of Computer Graphics

Download Shading - Computer Graphics - Lecture Notes | ECS 175 and more Study notes Computer Graphics in PDF only on Docsity!

Shading

1. Light sources
2. Basic illuminication models
3. Phong shading
4. Polygon shading
5. Global illumination (later)

Photorealistic rendering

1. accurate graphical representations of objects
2. good physical descriptions of the lighting effects in a scene Lighting effects:

− light reflection − transparency − surface texture − shadows

Modeling the colors and lighting effects that we see on an object is a complex process

approximation

Surface types

− Rough, grainy surfaces tend to scatter light

− Glossy, shiny surfaces result in highlighting effect

− Transparent surfaces can transmit light

Basic illumination models

1. Ambient light
   2. Diffuse reflection
   3. Specular reflection

− model the combination of light reflections from surrounding objects in the scene

− no spatial or directional characteristics

− background light

− account for all the complex ways in which light can reach an object that are not addressed in the other parts of the illumination equation

I = kaIa

Ambient light

where I is the intensity of the

ambient light, and ka (the ambient reflection coefficient ) is the percentage of ambient light reflected from the object’s surface

Specular reflection

− on any shiny surface

− appear white, the color of the incident light

− reflect light unequally in different directions

− on a perfectly shiny surface, light is relfected only in the mirrowed direction of L about N. N

L

R

θ θ V

Ι = Is ks (R V)

n

Ι = Ia ka + Ιd kd (Ν L) + Is ks (R V)

n

where n makes the specular highlight rapidly fall off

This is the Phong shading model!!

α