Class

• <DRM Image Mapping Function>

Superclass

• <DRM SEDRIS Abstract Base>

Subclass

• None.

Definition

An instance of this DRM class specifies how the given <DRM Image> instance is to be mapped onto a given textured object, including the mapping method, the projection, and how <DRM Texture Coordinate> instances (if present) are to be treated if they fall outside the image space bounded by the image indexes (0, 0) and (1, 1).

The image_mapping_method field specifies how to combine the referenced texture map with any <DRM Colour> instances on the textured object.

The image_wrap_s field specifies whether to clamp or repeat the given <DRM Image> instance in s.

The image_wrap_t field specifies whether to clamp or repeat the given <DRM Image> instance in t.

The image_projection_type field specifies the type of projection to be used when applying the given <DRM Image> instance to textured objects.

1. If planar projection is specified, the following cases may apply.

   1. The DRM object may have <DRM Texture Coordinate> instances or <DRM Tack Point> instances, in which case 7.2.42 Image mapping functions and texture coordinates applies.
   2. The <DRM Image Mapping Function> instance may have a <DRM Image Anchor> component.
   3. The <DRM Image> instance may have a <DRM Image Anchor> component.

2. If cylindrical or spherical projection is specified, the DRM object shall not have <DRM Texture Coordinate> instances or <DRM Tack Point> instances. Instead, either the <DRM Image Mapping Function> instance or its <DRM Image> instance shall have a <DRM Image Anchor> component.

The intensity_level field specifies the percent contribution of the <DRM Image Mapping Function> instance to the total effect on the textured object. For a <DRM Image> instance with a colour coordinate component specified by its signature, multiply first, second, and third colour coordinate values within the texels of the <DRM Image> instance by this value.

The value of the gain field is to be added to each colour data value from the texel data of the given <DRM Image> instance to obtain the displayed image.

The image_detail_mapping field specifies whether the <DRM Image Mapping Function> instance is used to describe mapping of a detail image on the textured object.

Class diagram

Figure 6.134 — DRM_Image_Mapping_Function

Constraints

• <DRM Image Anchor> SRF
• <DRM Presentation Domain> constraints
• Image mapping functions and texture coordinates
• Publishable object

Example(s)

• Consider the visualization of a tree. An image of a tree stored in a <DRM Image> instance is to be mapped onto a rectangular polygon represented by a <DRM Polygon> instance as depicted in Figure 6.135.

  

  Figure 6.135 — <DRM Image Mapping Function> example

  The <DRM Polygon> instance is composed of:

  1. a <DRM Image Mapping Function> component associated to the <DRM Image> instance containing the tree data, and composed of a <DRM Presentation Domain> component with presentation_domain = {OTW}. The fields of the <DRM Image Mapping Function> instance are specified as follows:

     image_mapping_method	REPLACE
     image_wrap_s	CLAMP
     image_wrap_t	CLAMP
     image_projection_type	PLANAR
     intensity_level	1,0
     gain	0,0
     image_detail_mapping	TRUE

  2. four <DRM Vertex> components, where each <DRM Vertex> component is composed of:

     1. A <DRM LSR 3D Location> component specifying the location coordinate of the <DRM Vertex> instance, and
     2. A <DRM Texture Coordinate> component specifying the texture coordinate of the vertex onto the texture map. The texture coordinate values for each vertex map to the [0,0, 0,0], [1,0, 1,0] range of texture coordinate space.

• Consider a <DRM Polygon> instance with two <DRM Image Mapping Function> components. One <DRM Image Mapping Function> component specifies the <DRM Image> instance displayed for most cases. The second <DRM Image Mapping Function> component, if instance, if image_detail_mapping is TRUE, specifies the imagery that is added to the <DRM Polygon> instance when the eyepoint is so close to the <DRM Polygon> instance that the main <DRM Image> instance texels are no longer useful for texturing the <DRM Polygon> instance.

• Considering <DRM Polygon> instance D representing the door of a truck that is painted brown, where the door has a forestry service logo on it. D has a <DRM Inline Colour> component that colours the polygon brown and a <DRM Image Mapping Function> component F that texture maps the logo onto the surface of the door representation as follows.

  F has image_mapping_method = DECAL.

  The logo image has 123COLOUR_ALPHA signature. The logo portion of the image has alpha = 1, the border of the logo has alpha = 0,5, and the background of the image outside the logo has alpha = 0,0. When F is applied to the surface of D, therefore, the logo replaces the brown colour since it has alpha = 1, the background of the logo is replaced by the brown colour since it has alpha = 0, and the border of the logo blends the logo colour with the brown colour since it has alpha = 0,5.