SoVRMLSpotLight -

#include <Inventor/VRMLnodes/SoVRMLSpotLight.h>

Inherits SoVRMLLight.

The SoVRMLSpotLight class defines a spot light source.

The detailed class documentation is taken verbatim from the VRML97 standard (ISO/IEC 14772-1:1997). It is copyright The Web3D Consortium, and is used by permission of the Consortium:.

  SpotLight {
    exposedField SFFloat ambientIntensity  0         # [0,1]
    exposedField SFVec3f attenuation       1 0 0     # [0,inf)
    exposedField SFFloat beamWidth         1.570796  # (0,pi/2]
    exposedField SFColor color             1 1 1     # [0,1]
    exposedField SFFloat cutOffAngle       0.785398  # (0,pi/2]
    exposedField SFVec3f direction         0 0 -1    # (-inf, inf)
    exposedField SFFloat intensity         1         # [0,1]
    exposedField SFVec3f location          0 0 0     # (-inf, inf)
    exposedField SFBool  on                TRUE
    exposedField SFFloat radius            100       # [0, inf)
  }
  .fi


The SpotLight node defines a light source that emits light from a specific point along a specific direction vector and constrained within a solid angle. Spotlights may illuminate geometry nodes that respond to light sources and intersect the solid angle defined by the SpotLight. Spotlight nodes are specified in the local coordinate system and are affected by ancestors' transformations.

A detailed description of ambientIntensity, color, intensity, and VRML's lighting equations is provided in 4.6.6, Light sources (<http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-IS-VRML97WithAmendment1/part1/concepts.html#4.6.6>). More information on lighting concepts can be found in 4.14, Lighting model (<http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-IS-VRML97WithAmendment1/part1/concepts.html#4.14>), including a detailed description of the VRML lighting equations.

The location field specifies a translation offset of the centre point of the light source from the light's local coordinate system origin. This point is the apex of the solid angle which bounds light emission from the given light source.

The direction field specifies the direction vector of the light's central axis defined in the local coordinate system.

The on field specifies whether the light source emits light. If on is TRUE, the light source is emitting light and may illuminate geometry in the scene. If on is FALSE, the light source does not emit light and does not illuminate any geometry.

The radius field specifies the radial extent of the solid angle and the maximum distance from location that may be illuminated by the light source. The light source does not emit light outside this radius. The radius shall be greater than or equal to zero.

Both radius and location are affected by ancestors' transformations (scales affect radius and transformations affect location).

The cutOffAngle field specifies the outer bound of the solid angle. The light source does not emit light outside of this solid angle.

The beamWidth field specifies an inner solid angle in which the light source emits light at uniform full intensity. The light source's emission intensity drops off from the inner solid angle (beamWidth) to the outer solid angle (cutOffAngle) as described in the following equations:


  angle = the angle between the Spotlight's direction vector 
          and the vector from the Spotlight location to the point 
          to be illuminated 

if (angle >= cutOffAngle): multiplier = 0 else if (angle <= beamWidth): multiplier = 1 else: multiplier = (angle - cutOffAngle) / (beamWidth - cutOffAngle)

intensity(angle) = SpotLight.intensity × multiplier .fi

If the beamWidth is greater than the cutOffAngle, beamWidth is defined to be equal to the cutOffAngle and the light source emits full intensity within the entire solid angle defined by cutOffAngle. Both beamWidth and cutOffAngle shall be greater than 0.0 and less than or equal to pi/2.

Figure 6.16 depicts the beamWidth, cutOffAngle, direction, location, and radius fields of the SpotLight node.

Figure 6.16 -- SpotLight node

SpotLight illumination falls off with distance as specified by three attenuation coefficients. The attenuation factor is

  1/max(attenuation[0] + attenuation[1]×r + attenuation[2]×r^2 , 1),
  .fi


where r is the distance from the light to the surface being illuminated. The default is no attenuation. An attenuation value of (0, 0, 0) is identical to (1, 0, 0). Attenuation values shall be greater than or equal to zero. A detailed description of VRML's lighting equations is contained in 4.14, Lighting model (<http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-IS-VRML97WithAmendment1/part1/concepts.html#4.14>). 

Public Member Functions

Static Public Member Functions

Public Attributes

Protected Member Functions

Static Protected Member Functions

SoVRMLSpotLight::SoVRMLSpotLight (void)

SoVRMLSpotLight::~SoVRMLSpotLight () [protected, virtual]

SoType SoVRMLSpotLight::getClassTypeId (void) [static]

SoType SoVRMLSpotLight::getTypeId (void) const [virtual]

  void foo(SoNode * node)
  {
    if (node->getTypeId() == SoFile::getClassTypeId()) {
      SoFile * filenode = (SoFile *)node;  // safe downward cast, knows the type
    }
    else if (node->getTypeId().isOfType(SoGroup::getClassTypeId())) {
      SoGroup * group = (SoGroup *)node;  // safe downward cast, knows the type
    }
  }

const SoFieldData ** SoVRMLSpotLight::getFieldDataPtr (void) [static, protected]

const SoFieldData * SoVRMLSpotLight::getFieldData (void) const [protected, virtual]

void SoVRMLSpotLight::initClass (void) [static]

void SoVRMLSpotLight::GLRender (SoGLRenderAction * action) [virtual]

SoSFVec3f SoVRMLSpotLight::location

SoSFVec3f SoVRMLSpotLight::direction

SoSFFloat SoVRMLSpotLight::beamWidth

SoSFFloat SoVRMLSpotLight::cutOffAngle

SoSFFloat SoVRMLSpotLight::radius

SoSFVec3f SoVRMLSpotLight::attenuation

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