Definition
The number of <Image Mapping Function>
instances referenced by a
<Geometry Representation> instance shall
equal the number of <Texture Coordinate>
components for each <Vertex> instance and
<Tack Point> instance within the
component tree rooted at that
<Geometry Representation> instance.
<Image Mapping Function> instances
referenced by <Feature Representation>
instances, on the other hand,
shall either have <Image Anchor> components, or
reference <Image> instances that have
<Image Anchor> components.
EXCEPTION:
<Image Mapping Function>
instance is used to specify a non-planar projection (such as spherical,
cylindrical), it shall use
an <Image Anchor> component, and the
<Geometry Representation> instance
to which the
<Image Mapping Function> instance
is attached cannot have
<Texture Coordinate> instances or
<Tack Point> instances within its component tree.
Rationale
The multiple <Image Mapping Function>
instances and multiple
<Texture Coordinate> instances
are ordered, and are defined to correspond to each other as if they were in
parallel arrays.
<Image Mapping Function> instances
referenced by a <Feature Representation>
instance are attributes for geometry that is to be
derived by the consumer for the
<Feature Representation> instance. Since
<Texture Coordinate> instances and
<Tack Point> instances are not applicable to
<Feature Representation> instances, such
<Image Mapping Function> instances
shall be specified with <Image Anchor>
components.
Example
Consider a triangular <Polygon> instance with one
<Image Mapping Function> instance
for the OTW domain. Each of the three
<Vertex> components of the <Polygon> instance
has one <Texture Coordinate> component,
specifying the (s,t) within the image space
that will be mapped to that <Vertex> instance.
Consider a triangular <Polygon> that has
different texture maps, one for OTW and one for thermal. The
<Polygon> thus has two ordered
<Image Mapping Function> instances,
so each of its <Vertex> components will have two ordered
<Texture Coordinate> components, one for
each <Image Mapping Function> instance.
FAQs
No FAQs supplied.
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