COMP GRAPHICS FINALS

Textures

• refer to images applied to surfaces of geometric shapes in three-dimensional scenes.

• For example, the figure below shows an image of a brick wall mapped to a triangle.

texture coordinate

specifies what part of the texture image to sample from

0 to 1

Texture coordinates in the x and y axis range from___ .

sampling

The process of retrieving the texture color using texture coordinates is known as

texels

pixels of the texture

mipmap

collection of texture images where each subsequent texture is twice as small compared to the previous one.

texture object

• a data structure that stores pixel data from an image

• stores information about which algorithms to use to determine the colors of the surface the texture is being applied to;

• this requires some type of computation whenever the texture and the surface are different sizes.

Lighting

• refers to the placement of lights in a scene to achieve a desired effect.

• It is one of the most important considerations for realistic 3D graphics.

• The goal is to simulate light sources and how the light they emit interacts with objects in the scene.

Ambient lighting

affects all points on all geometric surfaces in a scene by the same amount.

Diffuse lighting

represents light that has been scattered and thus will appear lighter or darker in various regions, depending on the angle of the incoming light.

Specular lighting

creates bright spots and highlights on a surface to simulate shininess, which is the tendency of a surface to reflect light.

illumination model

a combination of lighting types used to determine the color at each point on a surface.

Phong model

• One of the most commonly used illumination models

• which uses ambient, diffuse, and specular lighting, and is particularly appropriate for reflective or shiny surfaces.

1. the direction vector of the light ray

2. a vector perpendicular to the surface (normal vector).

The magnitude of the effect of a light source at a point depends on the angle at which a ray of light meets a surface.

This angle is calculated as the angle between two (2) vectors

point light

simulates rays of light emitted from a single point in all directions and incorporates attenuation.

Attenuation

is the decrease in intensity as the distance between the light source and the surface increases.

directional light

simulates a distant light source such as the sun, in which all the light rays are oriented along the same direction and there is no attenuation.

Shadows

• are areas hidden from the light source.

• They add great realism to a lit scene and make it easier for viewers to observe and estimate spatial relationships between objects.

• They give a greater sense of depth to the scene and objects.

Shading

When using lights, the colors on a surface may be brighter or dimmer, depending on the angle at which the light rays meet the surface. This effect is called ____ .

shadow pass

• The data required for creating shadows will be gathered in a rendering pass called ____.

• The purpose of it is to render the scene from the position and direction of the light source to determine what points are “visible” to the light.

shadow mapping

• in which the scene is rendered from the light's point of view.

• Everything seen from the light's perspective is lit and everything that cannot be seen must be in shadow.