SoGVRPointLight

InventorModule

author	MeVis Medical Solutions AG
package	MeVisLab/Standard
dll	SoGVR
definition	soGVR.def
see also	SoGVRVolumeRenderer
inherits from	SoGVRShaderParameterPosition
keywords	shader, pipeline

Purpose

The SoGVRPointLight adds a point light to the SoGVRVolumeRenderer. The light has a diffuse and specular intensity and uses the material properties (specularity, etc.) as specified in the volume renderer. It supports different attenuation modes to model how far the light reaches, which is turned off by default.

Usage

Any number of SoGVRPointLight modules can be placed in front of a SoGVRVolumeRenderer. Note that each light needs to have a unique Name in the same Open Inventor scene, so you should name the lights according to their role, e.g., headlight or highlight1.

The attenuation mode can be used to either highlight just a specific region, or to improve depth perception by adding attenuation to a headlight, e.g., for endoscopic rendering.

The light Position can be specified in world coordinates (to highlight special features of a dataset) or in eye/camera coordinates to attach the light to the camera (for a headlight).

Details

Examples showing the same point light for the different attenuation modes, the light position is shown as a sphere.

Attenuation off:

Linear/Quadratic attenuation:

Spherical attenuation:

Windows

Default Panel

Output Fields

self

name: self, type: SoNode

A node that must be placed in front of a SoGVRVolumeRenderer.

see also SoGVRShaderParameterPosition.self

Parameter Fields

Field Index

Attenuation Mode: Enum	Percentage: Float
Color: Color	Position: Vector3
Coordinate System: Enum	Specular Intensity: Float
Diffuse Intensity: Float	Use For First Hit: Bool
Enabled: Bool	Zero Intensity Distance: Float
Full Intensity Distance: Float
Half Intensity Distance: Float
Name: String

Visible Fields

Enabled

name: enabled, type: Bool, default: TRUE

If checked, the light is enabled.

see also SoGVRShaderParameterPosition.enabled

Name

name: name, type: String, default: pointLight1

Sets the name of the light; the name needs to be unique in the same Open Inventor scene.

see also SoGVRShaderParameterPosition.name

Coordinate System

name: coordinateSystem, type: Enum, default: WorldCoordinates

Sets the coordinate system in which the light Position is specified.

see also SoGVRShaderParameterPosition.coordinateSystem

Position

name: position, type: Vector3, default: 0 0 1

Sets the light position.

see also SoGVRShaderParameterPosition.position

Color

name: color, type: Color, default: 1 1 1

Sets the light color.

Diffuse Intensity

name: diffuseIntensity, type: Float, default: 1, minimum: 0, maximum: 1

Sets the diffuse intensity of the light.

Specular Intensity

name: specularIntensity, type: Float, default: 1, minimum: 0, maximum: 1

Sets the specular intensity of the light.

Use For First Hit

name: useForFirstHit, type: Bool, default: FALSE

Attenuation Mode

name: attenuationMode, type: Enum, default: ATTENUATION_OFF

Defines how the light intensity is attenuated by the distance to the light position.

Values:

Title	Name	Description
​Off	​ATTENUATION_OFF	​No attenuation.
​Linear Quadratic	​ATTENUATION_LINEAR_QUADRATIC	​A mix of linear and quadratic attenuation, specified by Percentage and Half Intensity Distance. linearFactor = (attenuationPercentage<50.f) ? attenuationPercentage/50 : (100-attenuationPercentage)/50; quadraticFactor = (attenuationPercentage<50.f) ? 0 : 1. - linearFactor linearAttenuation = attenuationHalfIntensityDistance / (attenuationHalfIntensityDistance + linearFactor * distanceToLight) quadraticAttenuation = attenuationHalfIntensityDistance2 / (attenuationHalfIntensityDistance2 + quadraticFactor * distanceToLight) attenuation = linearAttenuation * quadraticAttenuation
​Spherical	​ATTENUATION_SPHERICAL	​A spherical attenuation, specified by Full Intensity Distance and Zero Intensity Distance: attenuation = 1. - smoothstep(attenuationFullIntensityDistance, attenuationZeroIntensityDistance, distanceToLight)

Percentage

name: attenuationPercentage, type: Float, default: 50, minimum: 0, maximum: 100

Defines the percentage of attenuation in linear/quadratic mode.

Percentage	Description
0%	No attenuation
0% - 50%	0 to 100% linear attenuation
50%	full linear attenuation
50%-100%	mixes linear attenuation with quadratic attenuation
100%	full quadratic attenuation

Half Intensity Distance

name: attenuationHalfIntensityDistance, type: Float, default: 20, minimum: 0

Sets the approximate distance in millimeters at which the light has half its intensity. Only used if Attenuation Mode is set to “Linear Quadratic” attenuation.

Full Intensity Distance

name: attenuationFullIntensityDistance, type: Float, default: 20, minimum: 0

Sets the distance in millimeters up to which the light keeps its full intensity. Only used if Attenuation Mode is set to “Spherical” attenuation.

Zero Intensity Distance

name: attenuationZeroIntensityDistance, type: Float, default: 40, minimum: 0

Sets the distance in millimeters up to which the light falls off to zero, using hermite interpolation. Only used if Attenuation Mode is set to “Spherical” attenuation.