This group node renders its children multiple times applying different per-instance attributes.

This node issues a single multi-instance OpenGL draw call that automatically applies per-instance parameters (SoInstanceParameter objects) set in the parameters field. Some predefined parameter names can be used for common instance parameters like position, rotation, scale factor, or color. Parameter objects with these names are automatically managed and are recognized and used by the default shaders. Applications can define additional parameter objects to be used by custom shaders. Custom shaders can also be used to set per-instance colors and so on.

The predefined instance parameters are typically set by the application to position the instances in space. The application does not need to set predefined instance parameter values if the default values are OK. For example, you may not need to set per-instance rotations. In that case you can just set the desired parameters for translating and/or scaling instances. If the application does not set any instance parameters, all the instances will be drawn at the same 3D position without any rotation or scaling factor applied.

Some methods are provided by SoInstanceParameter to create these per-instance parameters: see the SoInstanceParameter and SoMFInstanceParameter documentation.

The predefined names for the SoInstanceParametername field are the following. However we recommend using the SoInstanceParameter static method getPredefinedParameterName() to ensure future compatibility.

• "OivShapeInstanceTranslation": Data is an array of SbVec3f translation values (3 floats) to apply to the instances.

• "OivShapeInstanceScale": Data is an array of SbVec3f scale factor values (3 floats) to apply to the instances.

• "OivShapeInstanceRotation": Data is an array of SbRotation values (4 floats representing a quaternion) to apply to the instances.

• "OivShapeInstanceColor": Data is an array of SbColor values (3 floats) to apply to the instances.

• "OivShapeInstanceVisibility": Data is an array of unsigned int32 values to apply to the instances.

The OivShapeInstanceTranslation, OivShapeInstanceScale and OivShapeInstanceRotation parameters (if present) are combined together to create an equivalent matrix. This matrix is available to application shader programs using the GLSL function

mat4 OivGetShapeInstanceMatrix()

The OivShapeInstanceColor parameter affects the diffuse color of each instance.

Notes:

• The number of elements in each SoVertexShaderParameter must be greater than or equal to numInstances*SoVertexShaderParameter.instanceDivisor. If not, the attributes will be ignored with warning messages in debug mode.

• Traversing the Nth child sets the current switch value to N , for use with inherited switch values (see SoSwitch).

• Although SoMultipleInstance is derived from SoGroup, it behaves like an SoSeparator (traversal state is pushed and popped).

Limitations:

• The only SoShape nodes that can currently be used are: SoBufferedShape and nodes derived from SoAlgebraicShape (e.g. SoAlgebraicSphere).

• Multiple instance nodes cannot currently be nested. SoMultipleInstance, SoMultipleCopy and SoArray nodes may not be children.

• This node requires at least version 3.3 of OpenGL.

FILE FORMAT/DEFAULT

MultipleInstance {

numInstances	1
numBatches	1
parameters

}

Reference