This node defines the lighting model to use when rendering subsequent shapes. The lighting model is specified in the OIV.Inventor.Nodes.SoLightModel.model field, which is PER_VERTEX_PHONG by default.

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

OIV.Inventor.Nodes.SoLightModel.Models.BASE_COLOR	OIV.Inventor.Nodes.SoLightModel.Models.PER_PIXEL_PHONG	OIV.Inventor.Nodes.SoLightModel.Models.PHYSICALLY_BASED

When the light model is not OIV.Inventor.Nodes.SoLightModel.Models.BASE_COLOR, there must be light nodes (e.g. OIV.Inventor.Nodes.SoDirectionalLight) in the scene graph for objects to be easily visible. When using the Open Inventor viewer classes (e.g. OIV.Inventor.Win.Viewers.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 OIV.Inventor.Nodes.SoEnvironment node to specify additional lighting options:

• The ambient light component of the Phong reflection model.

• Light attenuation for OIV.Inventor.Nodes.SoPointLight and OIV.Inventor.Nodes.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:

• OIV.Inventor.Nodes.SoPhysicalMaterial.baseColor

• OIV.Inventor.Nodes.SoMaterial.diffuseColor

• OIV.Inventor.Nodes.SoBaseColor.rgb

• OIV.Inventor.Nodes.SoPackedColor.orderedRGBA

• OIV.Inventor.Nodes.SoColorMap.colorMap

• OIV.Inventor.Nodes.SoBufferedShape.colorBuffer

• OIV.Inventor.Nodes.SoVertexProperty.orderedRGBA

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

mySoMaterial->diffuseColor = SbColor(1,0,0);
mySoMaterial->transparency = 0 ;

mySoPhysicalMaterial->baseColor = SbColorRGBA(1,0,0,1);

mySoBaseColor->rgb = SbColor(1,0,0);

mySoPackedColor->orderedRGBA = SbColorRGBA(1,0,0,1).getPackedValue();

mySoColorMap->colorMap.setValues(0, 4, new float[4]{ 1, 0, 0, 1 });

mySoBufferedShape->colorBuffer = new SoCpuBufferObject(new float[4]{ 1, 0, 0, 1 }, 4 * sizeof(float));

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
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 OIV.Inventor.Nodes.SoLightModel.Models.BASE_COLOR

• Objects are drawn using the base color only. There is no lighting.

• If a node related to the material is visited after OIV.Inventor.Nodes.SoBaseColor during the traversal, the rgb defined by the OIV.Inventor.Nodes.SoBaseColor may change.

• The base color is specified as described [above](OIV.Inventor.Nodes.SoLightModel-base-color-def).

• The OIV.Inventor.Nodes.SoMaterial fields are ignored except diffuseColor and transparency.

• The OIV.Inventor.Nodes.SoPhysicalMaterial fields are ignored except baseColor.

• The OIV.Inventor.Nodes.SoLight instances are ignored.

• The OIV.Inventor.Nodes.SoEnvironment instances are ignored.

Using OIV.Inventor.Nodes.SoLightModel.Models.PER_VERTEX_PHONG or OIV.Inventor.Nodes.SoLightModel.Models.PER_PIXEL_PHONG

• The lighting takes into account all fields of OIV.Inventor.Nodes.SoMaterial.

• If a node related to the material is visited after the OIV.Inventor.Nodes.SoMaterial during the traversal, the diffuseColor and transparency defined by the OIV.Inventor.Nodes.SoMaterial may change

• The base color is specified as described [above](OIV.Inventor.Nodes.SoLightModel-base-color-def).

• The OIV.Inventor.Nodes.SoPhysicalMaterial fields are ignored except baseColor.

• The OIV.Inventor.Nodes.SoLight instances are used.

• The OIV.Inventor.Nodes.SoEnvironment instances are used.

Using OIV.Inventor.Nodes.SoLightModel.Models.PHYSICALLY_BASED

• The lighting takes into account all fields of OIV.Inventor.Nodes.SoPhysicalMaterial.

• If a node related to the material is visited after the OIV.Inventor.Nodes.SoPhysicalMaterial during the traversal, the baseColor defined by the OIV.Inventor.Nodes.SoPhysicalMaterial may change

• The base color is specified as described [above](OIV.Inventor.Nodes.SoLightModel-base-color-def).

• The OIV.Inventor.Nodes.SoMaterial fields are ignored except diffuseColor and transparency.

• The OIV.Inventor.Nodes.SoLight instances are used.

• The OIV.Inventor.Nodes.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 OIV.Inventor.Nodes.SoShapeHints) determines the front face. To enable "two sided" lighting (lighting both front and back faces) see OIV.Inventor.Nodes.SoShapeHints.

# Light model and VolumeViz

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

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

FILE FORMAT/DEFAULT

LightModel {

model

PER_VERTEX_PHONG

}

ACTION BEHAVIOR

OIV.Inventor.Actions.SoGLRenderAction, OIV.Inventor.Actions.SoCallbackAction Sets the current lighting model in the state.

Reference