Class SoLightModel

  • All Implemented Interfaces:

    public class SoLightModel
    extends SoNode
    Node that defines the lighting model to use when rendering. This node defines the lighting model to use when rendering subsequent shapes. The lighting model is specified in the model field, which is PER_VERTEX_PHONG by default.

    SoLightModel supports several types of light model. The following images provide examples of rendering the same scene using a different light model.

    When the light model is not BASE_COLOR, there must be light nodes (e.g. SoDirectionalLight) in the scene graph for objects to be easily visible. When using the Open Inventor viewer classes (e.g. SoWinExaminerViewer), the viewer will create a "headlight" (directional light attached to the camera) if no other light nodes exist when setSceneGraph() is called. When using the Open Inventor viewer components (e.g. SceneExaminer), a "headlight" is automatically added to the scene graph.

    You can use a SoEnvironment node to specify additional lighting options:

    • The ambient light component of the Phong reflection model.
    • Light attenuation for SoPointLight and SoSpotLight nodes.
    • Ambient occlusion.

    # Definition of base color

    All the light models supported by Open Inventor use the concept of base color composed of 3 channels red green blue (rgb). It corresponds to the color of an object before being altered by light effects. Unfortunatly the term *base color* is not always used in the API and documentation, sometimes it is referred to as *diffuse color*, rgb color*, a *rgb* or just *color*.

    The following fields define the same concept of *base color* of an object:

    The following C++ code samples are equivalent and define a single red opaque base color:

     // using SoMaterial
     mySoMaterial->diffuseColor = SbColor(1,0,0);
     mySoMaterial->transparency = 0 ;
     // using SoPhysicalMaterial
     mySoPhysicalMaterial->baseColor = SbColorRGBA(1,0,0,1);
     // using SoBaseColor
     mySoBaseColor->rgb = SbColor(1,0,0);
     // using SoPackedColor
     mySoPackedColor->orderedRGBA = SbColorRGBA(1,0,0,1).getPackedValue();
     // using SoColorMap
     mySoColorMap->colorMap.setValues(0, 4, new float[4]{ 1, 0, 0, 1 });
     // using SoBufferedShape
     mySoBufferedShape->colorBuffer = new SoCpuBufferObject(new float[4]{ 1, 0, 0, 1 }, 4 * sizeof(float));
     // using SoVertexProperty
     mySoVertexProperty->orderedRGBA = SbColorRGBA(1,0,0,1).getPackedValue();

    Changing the value of any of those fields overrides the *base color* of an object. This means that if you set 2 different fields to specify a color, the current definition of a color during the scene graph traversal overrides the previous one. For instance, the following code sample specifies an opaque red color that overrides the semi opaque green.

     mySoPhysicalMaterial.baseColor.setValue(new SbColorRGBA(0,1,0,0.5f)); // semi opaque green color
     mySoMaterial.diffuseColor.setValue(new SbColor(1,0,0)); // red color
     myRoot.addChild(mySoMaterial); // this red material overrides the green color

    # Light model and property nodes

    According to the light model selected, the following notes explain what is taken into account in the scene graph, and what is ignored:

    Using model BASE_COLOR

    • Objects are drawn using the base color only. There is no lighting.
    • If a node related to the material is visited after SoBaseColor during the traversal, the rgb defined by the SoBaseColor may change.
    • The base color is specified as described [above](SoLightModel-base-color-def).
    • The SoMaterial fields are ignored except diffuseColor and transparency.
    • The SoPhysicalMaterial fields are ignored except baseColor.
    • The SoLight instances are ignored.
    • The SoEnvironment instances are ignored.


    • The lighting takes into account all fields of SoMaterial.
    • If a node related to the material is visited after the SoMaterial during the traversal, the diffuseColor and transparency defined by the SoMaterial may change
    • The base color is specified as described [above](SoLightModel-base-color-def).
    • The SoPhysicalMaterial fields are ignored except baseColor.
    • The SoLight instances are used.
    • The SoEnvironment instances are used.


    # Two side lighting

    By default, lighting is only computed for the "front" faces of the geometry, leaving the back face of the geometry dark. If the normal vector is specified, it determines the front face. If normals are computed by Open Inventor, the vertex ordering (see SoShapeHints) determines the front face. To enable "two sided" lighting (lighting both front and back faces) see SoShapeHints.

    # Light model and VolumeViz

    The SoLightModel node controls lighting for most VolumeViz shapes, but *not* for SoVolumeRender. The lighting for volume rendering is controlled by the SoVolumeRenderingQuality node.

    Two sided lighting is automatically enabled for "slice" shapes, such as SoOrthoSlice.

    File format/default:

    LightModel {

      model PER_VERTEX_PHONG

    Action behavior:

    SoGLRenderAction, SoCallbackAction Sets the current lighting model in the state.

    See Also:
    SoBaseColor, SoEnvironment, SoLight, SoDirectionalLight, SoPointLight, SoSpotLight, SoPhysicalMaterial, SoMaterial
    • Constructor Detail

      • SoLightModel

        public SoLightModel()
        Creates a light model node with default settings.