Symmetry

Introduction

TopoGun has symmetry support available for all the tools and for most of the commands that modify the geometry. Symmetry takes place across symmetry planes, which can be aligned to any of the X, Y and Z axes, but also along custom directions. The symmetry planes can be rotated or moved, to retopologize reference mesh parts not aligned to any of the world X, Y and Z axes, although with "local" symmetrical features.

Symmetry Planes

The default symmetry plane is ZY, which is perpendicular to the X axis. There are three symmetry planes created by default. They are aligned to the X, Y and Z world axes and positioned at the center of the global coordinate system. Note that these three default symmetry planes are readonly, so they cannot be modified. You must duplicate any of them in order to be able to change their position and/or direction.

Each symmetry plane has two attributes: a position and a direction. By editing these two, you can place and rotate the plane to better fit the reference mesh.

To activate symmetry, press the X default keyboard shortcut or click on Enable Symmetry, in the Options menu.
In case the reference mesh is not symmetrical across the ZY (X) plane, open the Symmetry Options panel from the Views menu and choose another symmetry plane from the list.

You can check if the selected symmetry plane is aligned correctly by moving the mouse cursor over the reference mesh, while the Symmetry Options panel is visible.
A black dot is drawn at the symmetrical position and a dark circle with the radius of the Symmetry Tolerance parameter, which is the radius TopoGun searches for symmetrical elements when working with the tools. As you move the cursor closer to the symmetry plane, you notice an orange line segment intersecting the plane. Its length is equal to the Zero Snap Distance.

Both Symmetry Tolerance and Zero Snap Distance parameters can be set in the Preferences window.

The intesection between the currently selected symmetry plane and the reference mesh is rendered as a black section. If the section is not visible, it means that the selected symmetry plane doesn't intersect with the reference mesh.

Custom Symmetry Planes

Sometimes, even if the reference mesh is symmetrical, it may not be centered and aligned to any of the default symmetry planes.

To move a symmetry plane to the center of the mesh, you must duplicate it first and then click on the Center button in the Symmetry Options plane.

Double click on the symmetry plane in the Symmetry Options panel list to rename it.

Besides centering the newly created symmetry plane, you can move it into a new position, with the Move To command.
The symmetry plane will be moved to the camera pivot point. If a mesh is active and it has a vertex selected, the plane will be moved to the selected vertex position.

You can use the Snap To Reference Vertices command to better place the vertex you want to move the symmetry plane to. The selected vertex is moved to the closest reference mesh vertex.

If the reference mesh is also rotated so no default symmetry plane is aligned to it, then you must set the plane's direction properly, using the Look At and/or the Align functions.

Look At rotates the plane in such a way that its direction is towards the camera pivot point (or the selected mesh vertex).

If the reference mesh has some complex, curved surfaces, then the Look At approach may not work properly.

The Align function moves the symmetry plane to the center position between the two selected mesh vertices and it also rotates it so that its direction is aligned with the segment between the two vertices.