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:¶

../../../Modules/Inventor/SoGVR/mhelp/Images/PointLightNoAttenuation.png

Linear/Quadratic attenuation:¶

Spherical attenuation:¶

../../../Modules/Inventor/SoGVR/mhelp/Images/PointLightSpericalAttenuation.png

Windows¶

Default Panel¶

../../../Modules/Inventor/SoGVR/mhelp/Images/Screenshots/SoGVRPointLight._default.png

Output Fields¶

self¶

name: self, type: SoNode¶: A node that must be placed in front of a SoGVRVolumeRenderer.

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.

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.

Coordinate System¶

name: coordinateSystem, type: Enum, default: WorldCoordinates¶: Sets the coordinate system in which the light Position is specified.

Position¶

name: position, type: Vector3, default: 0 0 1¶: Sets the light 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.