DICOM PS3.3 2019b - Information Object Definitions

C.11.31 Render Shading Module

Shading enhances the visual perception of a volume by adding reflection characteristics.

Table C.11.31-1 contains Attributes that describe the shading used in a rendered view.

Note

This Module assumes a Phong shading model [Phong 1975]. An implementation may use any appropriate shading model, translating these parameters into a similar meaning in the chosen shading model.The generation mechanism for the surface normals that are required for the Phong shading model is not specified by DICOM.

Table C.11.31-1. Render Shading Module Attributes

Attribute Name

Tag

Type

Attribute Description

Shading Style

(0070,1701)

1

The style of shading.

See Section C.11.31.1.

Ambient Reflection Intensity

(0070,1702)

1

Intensity of the ambient reflection in the relative range 0.0 to 1.0, inclusive.

Light Direction

(0070,1703)

1C

The direction light is traveling from a single white light source at infinity. Represented as a unit vector encoded as three coordinates (x,y,z) in the VPS-RCS.

Required if Diffuse Reflection Intensity (0070,1704) or Specular Reflection Intensity (0070,1705) is present.

Diffuse Reflection Intensity

(0070,1704)

3

Intensity of the diffuse reflection in the relative range 0.0 to 1.0, inclusive.

If absent, a value of zero is assumed.

Specular Reflection Intensity

(0070,1705)

3

Intensity of the specular reflection in the relative range 0.0 to 1.0, inclusive.

If absent, a value of zero is assumed.

Shininess

(0070,1706)

3

Specifies the roughness of the rendered surfaces, in the relative range 0.0 to 1.0, inclusive. A value of 0.0 represents a rough surface and a value of 1.0 represents the smoothest surface which can be generated by the implementation.

Note

In theory, the range of shininess is from 0 to infinity. However, in practice each implementation has a finite upper limit for shininess. The implementation is expected to multiply this value by its upper limit value and use the result in its shading algorithm for shininess.

If absent, the shininess is an implementation decision.


C.11.31.1 Shading Style

The Shading Style (0070,1701) determines if the shading calculations are performed for all voxels, based on the facing of the surface normal which has been generated for that voxel:

Enumerated Values for Shading Style (0070,1701):

SINGLESIDED

Only "front-facing" voxels are shaded.

DOUBLESIDED

"Front-facing" and "back-facing" voxels are shaded.

Note

"Front-facing" voxels are those with a negative dot product between the surface normal which has been generated for that voxel and the vector between the Viewpoint Position (0070,1603) and the ViewPoint LookAt Point (0070,1604). "Back-facing" voxels are those with a positive dot product.

DICOM PS3.3 2019b - Information Object Definitions