Table 6.274 — DRM_Texture_Coordinate

Property

Description

Class

  • <DRM Texture Coordinate>

Superclass

Subclass

  • None.

Definition

An instance of this DRM class specifies an {s, t} tuple in image space (also known as texture space) used to specify the location of an individual texel within an image.

Each MIP level of a 2D <DRM Image> instance defines an image that has a width and height specified in texels. Regardless of the actual size of the image, the image space is defined by treating the 2D image as a square, defined by the lower left coordinate of (0,0, 0,0) and the upper right coordinate of (1,0, 1,0). A <DRM Texture Coordinate> instance is a coordinate within this image space.

A <DRM Texture Coordinate> instance specifies an exact location within a given image space, and this location is mapped to the object space location associated with the <DRM Vertex> instance, <DRM Point> instance, or <DRM Tack Point> instance of which the <DRM Texture Coordinate> instance is a component. A textured geometric DRM object generally has a <DRM Texture Coordinate> instance for each vertex of the object. The image is mapped to the DRM object by interpolating between the various texture coordinates specified at the vertices.

Whether a specified <DRM Texture Coordinate> instance corresponds to exactly one texel in the texture definition or to a blending of many texel values from the definition is a decision made by the texture interpolation algorithm used to display the texture. The methods for calculating the interpolated texture values and for blending the texture onto the object are determined by a <DRM Image Mapping Function> instance.

NOTE  According to 7.2.42 Image mapping functions and texture coordinates, <DRM Texture Coordinate> instances only appear within the scope of some <DRM Image Mapping Function> instance.

The s field specifies the s value of the {s,t} texture coordinate. For a <DRM Texture Coordinate> instance with a <DRM Texture Coordinate Control Link> component X, where the s_expression_index field of X is non-zero, the value of the s field is obtained from X.

The t field specifies the t value of the {s,t} texture coordinate. For a <DRM Texture Coordinate> instance with a <DRM Texture Coordinate Control Link> component X, where the t_expression_index field of X is non-zero, the value of the t field is obtained from X.

Class diagram

Figure 6.342 — DRM_Texture_Coordinate

Inherited field elements

Field name

Range

Field data type

None

   

Field elements

Field name

Range

Field data type

s

 

Long_Float

t

 

Long_Float

Default field values

Default field values for DRM_Texture_Coordinate

Associated to (one-way) (inherited)

  • None.

Associated to (one-way)

  • None.

Associated by (one-way) (inherited)

  • None.

Associated by (one-way)

  • None.

Associated with (two-way) (inherited)

  • None.

Associated with (two-way)

  • None.

Composed of (two-way) (inherited)

  • None.

Composed of (two-way)

Composed of (two-way metadata) (inherited)

  • None.

Composed of (two-way metadata)

  • None.

Component of (two-way) (inherited)

  • None.

Component of (two-way)

Constraints

Clarifications

None.

Example(s)

  • Consider a rectangular <DRM Polygon> instance P representing the location of a logo on the side of an airplane. P has a <DRM Image Mapping Function> component that describes how the logo represented by a <DRM Image> instance is to be mapped. Each vertex of P has a <DRM Texture Coordinate> component that specifies the position in the image that corresponds to that vertex.

  • Consider a complicated <DRM Polygon> instance representing the continent of North America. A <DRM Texture Coordinate> instance specifies a lower left corner of a satellite image that corresponds to the a position on the <DRM Polygon> instance specified by a <DRM Tack Point> instance so that the satellite image is properly displayed on top of the polygon.