Package com.openinventor.inventor.nodes

Class SoLightModel

  • All Implemented Interfaces:
    SafeDisposable
    public class SoLightModel
extends SoNode
    Node that defines the lighting model to use when rendering. This node defines the lighting model to be used when rendering subsequent shapes. The lighting model is specified in the model field which is PER_VERTEX_PHONG by default.

    Several types of light model are supported and the following images are examples of rendering of 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.

    An SoEnvironment node can be used to specify additional options related to lighting:

    • 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 by 3 channels red green blue (rgb). It corresponds to the color of an object before being altered by light effects. Unfortunatly the term of *base color* is not always used in the API and documentation, sometimes it can be a mentionned as *diffuse color*, sometimes it can be a *rgb color*, a *rgb* or just a *color*.

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

    Thus, the following code C++ 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();

    Moreover, changing the value of any of those fields override the *base color* of an object. It means that if 2 different fields are set 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
 mySoMaterial.transparency.setValue(0);
 myRoot.addChild(mySoPhysicalMaterial);
 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 the 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

    Using PER_VERTEX_PHONG or PER_PIXEL_PHONG

    • 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

    Using PHYSICALLY_BASED

    # Two side lighting

    By default, lighting is only computed for the "front" faces of geometry, so the back face of the geometry will be dark. The front face is determined by the normal vector, if specified, or by the vertex ordering (see SoShapeHints) if normals are computed by Open Inventor. 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_PIXEL_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.