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Creating vs. editing prims
This node belongs to a class of nodes that create or edit USD prims directly. These nodes operate in Create mode or Edit mode. This is controlled by a Create primitives checkbox or a Create/Edit popup menu. In create mode, the node creates new prims. In edit mode, the node changes the attributes on an existing prim.
Parameters that correspond to a USD attribute have a pop-up menu to the left that controls how the node authors the attribute.
Pop-up menu item
Set or Create
Sets the attribute to the given value, whether it previously existed or not.
Set If Exists
Only set the attribute to the given value if it previously existed.
Use this mode to make sure an attribute is only set on primitives of the correct type. For example, only
Makes the attribute appear to not exist, so it takes on its default value. (If the attribute doesn’t already exist on the prim, this does nothing.)
Ignore this parameter, don’t create or change the attribute in any way.
Editing the camera in the viewport
Enter the Camera state
Select the Camera node in the network, then in the viewport click the Handles tool, or press Enter.
⇧ Shift + T
Depth of field
⇧ Shift + F
Cameras in USD are always "Y up", regardless of the stage’s orientation, and look down the -Z axis.
Whether this node should create new prims, or edit existing prims.
In create mode, this lets you control where in the scene graph to create the prim(s).
The default is usually
/$OS. This creates a primitive at the root level with the same name as the node (for example,
/tube1). This is a useful default for preventing naming conflicts, but terrible for organization. You should try to remember to change the Primitive path to a better value when you create prims.
For example, instead of naming models after the node that created them, you might want to name them after the geometry inside, and organize them under a
The "Create primitives" section contains basic controls for how to create the new prim(s).
In edit mode, the node has a Primitive pattern parameter. This lets you specify the prim(s) the node should operate on. You can click the select button beside the text box to select the primitives from the scene graph tree. You can also use primitive patterns for advanced matching, including matching all prims in a collection.
How the transform parameters below apply to the primitive. (Because each USD prim can contain multiple transforms, and be affected by parent transforms, there are many different ways to apply new transforms.)
Apply the parameters as a new, most local transform.
Apply the parameters as a new, least local transform.
Overwrite or Append
If a local transform exists with the name
xformOp:transform, overwrite it with the parameters. Otherwise, apply it as a new, most local transform.
If this replaces an existing transform, that transform’s order in the local transform stack is not affected.
Overwrite or Prepend
Like "Overwrite or Append", but least local.
Apply Transform in World Space
Apply the parameters as a new, most local transform. However, prior to applying the transform, it is updated so that the result of the transform appears as if the transform was being applied in world space, before any local or ancestor transformations were applied to the primitive.
Replace All Local Transforms
The transform specified in the remaining transform parameters is always applied as a new transform. Prior to applying this transform, all existing transform operations on the local transform stack are cleared so that only the supplied transform remains on the local transform stack (though ancestor transforms still have an effect).
The order in which Houdini applies translates, rotates, and scales, and the order in which it applies rotation.
Movement amount along XYZ axes.
Degrees rotation around XYZ axes.
Non-uniform scaling along XYZ axes.
Scales the object uniformly along all three axes.
Moves the local origin of the object.
Rotates the local origin of the object after translation.
USD currently does not have look-at constraints. This node calculates the per-frame transform to fulfill the constraint and applies it to the object.
See the Light tool help for how to set up the look-at constraint interactively in the viewport.
Enable Look At
Turns on the constraint that orients this object to look at a point or another object.
Look At Position
If Enable look at is on and, this is a point in space this object will look at. If Look at primitive is not blank, this is an offset from the centroid of the target object (in the local space of that object).
Look At Primitive
The path to a USD prim this object should look at. If this is not blank, Look at position is an offset from this centroid of the target object.
Up Vector Method
Controls how the up vector is set.
Use (1,0,0) as the up axis.
Use (0,1,0) as the up axis.
Us the value of the Up Vector parameter as the up axis.
When Up vector method is "custom", this is the up axis to use for the look-at constraint.
A twist rotation (around the -Z axis, clockwise, in degrees), applied after the lookout transform.
Whether the view through this camera is perspective or orthographic.
Perspective focal length (in tenths of a world unit).
Horizontal aperture (in tenths of a world unit).
Vertical aperture (in tenths of a world unit).
Horizontal Aperture Offset
Horizontal offset of the aperture from the center of the image defined by the view frustum (expressed in tenths of a world unit).
Vertical Aperture Offset
Vertical offset of the aperture from the center of the image defined by the view frustum (expressed in tenths of a world unit).
Don’t show geometry closer than the near distance or farther away than the far distance (in world units).
Shutter-open time, relative to the start of frame, in
UsdTimeCode units. This is used to calculate motion blur. You can use a negative value to indicate that the shutter opens before each frame.
Shutter-close time, relative to the start of frame, in
UsdTimeCode units. If this is not greater than Shutter open there the shutter will never open and the renderer will produce a black image.
Distance from the camera to the focal plane, in world units.
Lens aperture. Default is
0, which turns off focusing.