ZBrush: Transpose, Masks and Subtools

Transpose 

Allows for the repositioning and moving of models within ZBrush. This allows for movement, scaling and rotation. When the Transpose tool is activated, a pivot appears in the model you are moving. Thic contains arrows, axis rings and block shapes. Pulling on the arrows of the Transpose tool moves a model. Axis rings allow for rotation and the block shapes allow for scaling. These are all measured on the X, Y and Z axis. 

There are also a number of options that allow for the Transpose tool to be customised. The Lock 
Gear: Allows access to deformers.
Pin: Pins the pivot to its current location.
Locator: Centres pivot to unmasked areas of the model. 

Home: Centres the pivot on the model.
Circle Arrow: Reset rotation of pivot
Lock: Unlocks the pivot, allowing for the pivot to be moved independent of the model. This allows for the centre of rotation to be changed, 
Checkbox: Transpose multiple models at once.

Masks

Masks allow for areas of a ZBrush model to be protected from manipulation, as masked areas cannot be influenced by Brushes. Adding a Mask itself uses the MaskPen Brush. Holding the CTRL key brings up this Brush and allows for Masks to be drawn over the model. 

CTRL + Click outside the model inverts the Mask selection.

CTRL + Click/Drag outside the model draws a flat selection over the model, with the area inside this selection having a Mask drawn over it. 
Holding CTRL+ALT reverses the Mask Brush, allowing for Masks to be erased. 
 Mask gradients can also be created to assist in the sculpting of fine details. Masks can be blurred by simply clicking using the Mask Brush. Alternatively, Masks can be sharpened by clicking with CTRL+ALT. 
CTRL+ Click and drag across the model to create a wide masked area. This functions like a select box and has a sharp edge.

I utilised the Mask tool to create horns on a model of a human head, one of the basic demo projects for ZBrush. This allowed me to add to the model whilst not influencing the other regions of it, creating horns whilst not damaging the face or scalp. Whilst doing this I noticed that the geometry of the horns became incredibly pinched and warped, because the Brushes I was using were pulling sharply upon geometry whilst not adding anything to the model, creating sharp edges and vertices.
To clear this sharp geometry up I turned on the "DynaMesh" function, adding sculpting geometry to the model. I found that this did not work whilst a Mask was active, as the DynaMesh influenced the entirety of the model. As such, when activating DynaMesh I removed all Masks and then worked on the horns themselves, sculpting them utilising the sculpting geometry of the DynaMesh.

IMM Primitives / Subtools

IMM Primitives are primitive shape models that can be brought into a Project. These do not impact the geometry of additional meshes in the Project. IMM Primitives can be found within the brush selection picker and are dragged in like primitive Tools. 

This also creates a Mask over other meshes in the Project, allowing for the IMM Primitive to be manipulated whilst not impacting pre-existing meshes. IMM Primitives can also be Transposed independently of pre-existing meshes. 

IMM Primitives placed into a Project can be used as Subtools - models that differ from the primary Tool with independent meshes and properties.

I utilised an IMM Primitive to create a mandible for the skull I made the week prior. I did this by creating an IMM Primitive capsule and using the move tool in accordance with symmetry to create the divergent shapes of the mandible. Using the Transpose pivot I was then able to move, scale and rotate the mandible into a shape which fit better with the scale of the skull. 

IMM Primitives may be used to add further detail to models, allowing for multiple different Tools to be present within the same Project. I will likely use these to sculpt disparate elements of a complex model.