V-Ray Render ID

The Render ID Render Channel creates selection masks based on the node handle of each object or the V-Ray assigned render ID. In Houdini, each object is internally assigned a unique node handle when the object is created. When V-Ray is rendering, each object is assigned a render ID. The intended use for the Render ID channel is to quickly create masks, based on the node handles or the render IDs, for various objects in a scene without having to set up a separate Multi Matte Render Channel for them. A wide variation of colors is used so no two objects will have the same color in the render element.

Node handles and render IDs are not the same as the Object ID: The node handle is assigned by Houdini (and can only be changed by Houdini internally), and the render ID is assigned by V-Ray during rendering only. Meanwhile, the Node ID is assigned by the user and can be changed at any time. In addition, while several objects can be assigned the same Object ID, each node handle and render ID are unique to a specific scene object. To create a channel that renders object colors based on node IDs, use the Node ID Render Channel.

Node handle numbers do not ever change, even if objects are deleted; a node handle number for a deleted object is simply no longer used. Specific node handle values can be retrieved using Python commands, but it is not necessary to do this to use the Render ID Render Channel.

There is no anti-aliasing with the Render ID Render Channel; where the edge of one object meets another object, the pixel color at that spot is the color from the object that contributes most to the pixel value.

The parameters for this render channel appear in the Parameters tab under the out Network and within the render elements node.

Name – The text added to the end of the rendered file, when saved as a separate file (e.g. myrender.Render_ID.vrimg).

Deep Output – Specifies whether to include this render element in deep images.