To make sketching and modeling easier, use snaps and inference points to accurately create, place, and edit geometry. You can use whatever axis you choose as the axis on which to draw or execute another action, such as extruding a surface. When executing a command, such as drawing a line, you will get a grip control. It represents your input point. This point may then snap to existing geometry.
There are several snaps that can aid you while you are sketching and modeling. Snapping to objects is automatically enabled, and you can snap to:
Edges. When hovering the grip over the edge, small red dots will be drawn at the ends and at the mid point.
Edge mid points
The plane of a face. When hovering the grip over the face a small red dot will be drawn at the face centroid. This will make it easy to find that point, if you want to snap to it.
The work plane, if you don't snap to anything else.
Circle or arc centers
The plane of a mesh facet.
To snap to the grid, you must enable the Snap to Grid toggle from the Settings menu.
Automatic selection of inference points is always enabled and will help you constrain the movement of geometry. Inference axes are generated by tools automatically or when you hover the grip over edges or points. Inference axes are always drawn on the screen with dashes so that you know where they are and are easy to snap to.
Axis: You can move geometry along the X, Y, or Z axis. The X-axis inference is red, the Y-axis is green, and the Z-axis is blue.
Axis Locking: You can lock movement along the X, Y, or Z axis. While dragging on an axis inference tap a second finger, or press hard with the pen. Then drag the grip to snap and inference to other elements.
Parallel: You can sketch or move geometry parallel to existing elements. Perpendicular inferences are purple. You need to hover your grip over a line you want to use as a parallel reference.
Perpendicular: You can also draw or move geometry perpendicular to existing elements. Perpendicular inferences are purple. You need to hover your grip over a line you want to use as a perpendicular reference.
Extending from a point: You can also use inferences to extend from a point reference. Hover the grip over a point you want to use as a reference until the tooltip appears, then use the inference axis that extends from the point.
Circle Center: If you want to snap to the center of an arc or circle, hover the grip over the arc or circle. This will show a small red dot at the center. It will stay visible for about 5 seconds after you move away from the arc or circle. Now move the grip over the red dot to snap to the center.
True arc and spline midpoints: When you hover the grip over a circle, arc or spline you will be able to snap to the true midpoint. It and the end points will be shown by a small red dot. When inferencing on an arc you will also snap to the vertices of the straight edges that represent the arc.