This is a projection manifold for tri-planar mapping. This techniques is also sometimes called "blended cube". It is often used to texture large environment without having to worry about UVs.
PxrRoundCube computes texture coordinates (uv) based on an object's surface position and orientation and can handle up to 6 sets of coordinates. It also outputs blending weights to be used by PxrMultiTexture.
PxrRoundCube only defines texture mapping coordinates and MUST be connected to a PxrMultiTexture pattern. To do so, connect PxrRoundCube.resultMulti to PxrMultiTexture.manifoldMulti. See maya example below.
You can choose to project 1, 3 or 6 images. The table below shows which textures will be used by the PxrMultiTexture node.
Manifold
Frequency
The frequency at which the texture will repeat. A value of 1 indicates that the texture will not repeat.

Tech Notes
| float frequency |
Default | 1.0 |
Transition Width
The filename of the texture for the Y axis. This parameter must be supplied if you chose to project 3 textures.

Tech Notes
RIB | float transitionWidth |
Default | 0.5 |
Pref
The name of the reference position primvar (Maya uses __Pref). The position reference may be used to keep the texture anchored to the surface while the object is deforming. If your deforming object is textured with PxrRoundCube, you need __Pref AND __Nref !

Nref
The name of the reference normal primvar (Maya uses __Nref). The normal reference may be used to keep the texture anchored to the surface while the object is deforming. If your deforming object is textured with PxrRoundCube, you need __Nref AND __Pref !
Coordinate System
Name of coordinate system transform (e.g. place3dtexture node in Maya). You can either use one of the predefined spaces ("world", "object", "current", etc) or the name of a coordinate system node in your scene. If empty, PxrRoundCube use "object" space.
Tech Notes
RIB | string coordsys |
Default | "" |
Use Undisplaced Position
When an object is displaced using PxrRoundCube, textures used during shading by the bxdf will not line up correctly with regard to the displacement map. The reason is simple : the displacement shader has moved P and the patterns attached to the bxdf are using the displaced P instead of the original. To avoid this problem, enable useUndisplacedPosition and the pattern will use the undisplaced position (Po) instead of the current position (P). Note that, under the hood, PxrRoundCube also uses the original normal (Non) instead of the current normal (N) when this is enabled.
Tech Notes
RIB | int useUndisplacedPosition |
Default | 0 |
Randomize
Sometimes, it is useful to randomize some of the parameters to make things look more natural...
Random Source
For each object to get a different variation, you need to select something unique about them to create a unique seed. You have a choice between the object's id and the object's name. These attributes are created by the software outputing the RIB and depending on your host, one may work better than the other.
Value | Meaning | Depends on |
---|
0 | Object ID | Attribute "identifier" "float id" |
1 | Object Name | Attribute "identifier" "string name") |
Tech Notes
RIB | int randomSource |
Default | 0 |
When set to zero, all PxrRoundCube patterns operating on the same node will compute the same random seed. If you want one of these patterns to compute a different variation, set the randomExtraSeed to a non-zero value.
Tech Notes
RIB | float randomExtraSeed |
Default | 0.0 |
Random Orientation
Set this parameter to 1 to randomly rotate the tri-planar projection. By default, the axes will be in object-space. This means that 3 spheres with the same PxrRoundCube pattern will look exactly the same. When you randomize the axes' orientation, they all look different, even though they might have the same transform. Typically, this is useful to control random variations of a lot of objects (think "rocks on the ground") from a single source.

Tech Notes
RIB | int randomOrientation |
Default | 0 |
Random Flip
This switch will randomly flip st coordinates of each axis of the tri-planar projection.

Tech Notes
RIB | int randomFlip |
Default | 0 |
Random Offset
This switch will randomly offset st coordinates of each axis of the tri-planar projection. You should probably make sure seams are not visible your texture is tiling.

Tech Notes
RIB | int randomOffset |
Default | 0 |
X Axis
Enable X
Enable or disable textures on the X axis.
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Scale S
Scale the textures on the X axis in the s direction (horizontal).
Tech Notes
RIB | float scaleSX |
Default | 1.0 |
Scale T
Scale the textures on the X axis in the t direction (vertical).
Tech Notes
RIB | float scaleTX |
Default | 1.0 |
Offset S
Offset the textures on the X axis in the s direction (horizontal).
Tech Notes
RIB | float offsetSX |
Default | 0.0 |
Offset T
Offset the textures on the X axis in the t direction (vertical).
Tech Notes
RIB | float offsetTX |
Default | 0.0 |
Invert S
Flip the textures on the X axis in the s direction (horizontal).
Tech Notes
RIB | float invertSX |
Default | 0.0 |
Invert T
Flip the textures on the X axis in the t direction (vertical).
Tech Notes
RIB | float invertTX |
Default | 0.0 |
Swap ST
Swap the s and t direction on the X axis. This is equivalent to a 90 degree rotation.
Tech Notes
RIB | float swapSTX |
Default | 0.0 |
Pivot S
Position in s of the scaling center on the X axis.
Tech Notes
RIB | float pivotSX |
Default | 0.0 |
Pivot T
Position in t of the scaling center on the X axis.
Tech Notes
RIB | float pivotTX |
Default | 0.0 |
Y Axis
Same controls for Y axis.
Z Axis
Same controls for Z axis.
The struct outputing all required information for a PxrMultiTexture pattern.