This node defines the current surface material properties for all subsequent shapes. OIV.Inventor.Nodes.SoMaterial sets several components of the current material during traversal. The ambientColor, diffuseColor, emissiveColor, specularColor and shininess fields are interpreted according to the classic OpenGL lighting model. The transparency field is effectively the inverse of "opacity" or "alpha value".

If lighting is turned off (OIV.Inventor.Nodes.SoLightModel set to BASE_COLOR), only the diffuse color and transparency fields are used to render geometry.

Multiple values can be specified for the OIV.Inventor.Nodes.SoMaterial.diffuseColor and OIV.Inventor.Nodes.SoMaterial.transparency fields. Different shapes interpret materials with multiple values differently. To bind materials to shapes, use an OIV.Inventor.Nodes.SoMaterialBinding node.

Several other nodes can be used to set diffuse color and transparency for geometry.

If the other color values are not needed, these nodes use a little less memory than an OIV.Inventor.Nodes.SoMaterial node, especially if multiple color values are specified. Generally OIV.Inventor.Nodes.SoVertexProperty is the most efficient mechanism and may provide better performance than using OIV.Inventor.Nodes.SoMaterial. Note that for these nodes transparency is set as "alpha value" (inverse of transparency).

• Diffuse color (only) can also be specified using an OIV.Inventor.Nodes.SoBaseColor node.

• Diffuse color and transparency can also be specified using an OIV.Inventor.Nodes.SoPackedColor node.

• Diffuse color and transparency can also be specified for polygonal geometry using the orderedRGBA field of OIV.Inventor.Nodes.SoVertexProperty.

The color components specified for lights mean something different than for materials. For a light, the numbers correspond to a percentage of full intensity for each color. If the R, G, and B values for a light's color are all 1.0, the light is the brightest possible white. If the values are 0.5, the color is still white, but only at half intensity, so it appears gray. If R=G=1 and B=0 (full red and green with no blue), the light appears yellow. The intensity can also be modulated using the OIV.Inventor.Nodes.SoLight.intensity field.

For materials, the numbers correspond to the reflected percentages of those colors. So if R=1, G=0.5, and B=0 for a material, that material reflects all the incoming red light, half the incoming green, and none of the incoming blue light. In other words, if an OpenGL light has components (LR, LG, LB), and a material has corresponding components (MR, MG, MB), then, ignoring all other reflectivity effects, the light that arrives at the eye is given by (LR*MR, LG*MG, LB*MB). As a result, for example, shining a pure blue light on a pure red cone has no visible effect.

Similarly, if you have two lights that send (R1, G1, B1) and (R2, G2, B2) to the eye, the components are added, giving (R1+R2, G1+G2, B1+B2). If any of the sums are greater than 1 (corresponding to a color brighter than the hardware can display), the component is clamped to 1.

To force all geometry following/below this node to use specific color and transparency values, call the OIV.Inventor.Nodes.SoMaterial.SetOverride(System.Boolean) method with true. Overriding the diffuse color and transparency overrides the color and transparency values in other nodes including OIV.Inventor.Nodes.SoPackedColor and OIV.Inventor.Nodes.SoVertexProperty. This can be useful, for example, to highlight a selected object.

It is also possible to override only a subset of the OIV.Inventor.Nodes.SoMaterial fields. If, for example, you only want to override the diffuse color, but not the other values, call setIgnored(true) on the fields that you do not want to override. But note that this selective override technique only works on other OIV.Inventor.Nodes.SoMaterial nodes! For OIV.Inventor.Nodes.SoPackedColor and OIV.Inventor.Nodes.SoVertexProperty, the diffuseColor and transparency values are bound together and cannot be overridden separately.

The default transparency algorithm is NO_SORT. To get a nice appearance for transparent objects you must change this to another value, for example, OPAQUE_FIRST or SORTED_PIXEL, using the setTransparencyType method in the Viewer class. See OIV.Inventor.Actions.SoGLRenderAction for a discussion of transparency algorithms and rendering order.

For scalar (non-RGBA) volumes, the color and alpha value of a voxel is affected by two nodes. OIV.Inventor.Nodes.SoMaterial's diffuseColor field specifies the "base" color and alpha values for all voxels. OIV.LDM.Nodes.SoTransferFunction specifies color and alpha values based on the voxel value. The final voxel color and alpha (before lighting and other effects) is computed by multiplying these two color and alpha values. The default material is 0.8, 0.8, 0.8, 1 (fully opaque gray). The 0.8 value for R, G and B allows lighting to increase the brightness of the voxel. For slice rendering without lighting, the application may want to set the material to 1, 1, 1, 1 so that only the OIV.LDM.Nodes.SoTransferFunction affects the voxel color and alpha. Effectively the material alpha value (aka transparency) is a "global" multiplier that can be used to increase or decrease the transparency of all voxels in the volume.

FILE FORMAT/DEFAULT

Material {

ambientColor	0.2 0.2 0.2
diffuseColor	0.8 0.8 0.8
specularColor	0 0 0
emissiveColor	0 0 0
shininess	0.2
transparency	0

}

ACTION BEHAVIOR

OIV.Inventor.Actions.SoGLRenderAction, OIV.Inventor.Actions.SoCallbackAction Sets the ambient color, the diffuse color, the specular color, the emissive color, the shininess, and the transparency of the current material. Sets: OIV.Inventor.Elements.SoMaterialElement

Reference