# Intersection Constraints

#### Intersect Constraints Types

The Intersect constraints determine the closest point and ray intersections with lines, planes, and surfaces. These constraints are different from other constraints in that Modo creates a new constrained item when the constraint is applied, rather than being specified in advance from the selected items.

**Intersect Line-Two Items**: This creates a new locator at the closest point along an infinite line that runs through the world center positions of two selected items.

**Intersect Line-Linear Curve**: This creates a new locator at the closest position along a user-generated linear curve, which is a curve defined by only two vertices.

**Intersect Plane**: This constraint creates a new locator at the closest point (by default) from the first selected item to an infinite plane derived from the world axes of the second selected item. You can change the default axis plane by adjusting the **Plane** setting.

**Intersect Surface**: You can use this constraint to project a closest point or ray intersection from an item to a mesh surface. Select the item (as the source of the intersection) and then a Mesh Item. Modo creates a new locator at the closest point on the surface from the driver item.

#### Intersection Constraint

**Mode**: Specifies whether Modo performs a **Closest** point or **Ray** intersection to determine the item's position along the line. The **Closest** point intersection indicates the closest point along the line to the constrained item. A **Ray** intersection intersects the line along the chosen axis and takes in to account the item's position and rotation transform values.

**Axis**: When the **Mode** is set to **Ray**, this defines which axis channel on the driver item Modo uses to project the ray.

**Negative Axis**: Selecting this, inverts the defined **Axis** from the default positive direction to a negative direction.

**Plane**: For a Plane intersection, this selection (such as **XZ**) defines the plane.

**Length**: This value is different when used with a line intersection or plane intersection. When used with a line intersection, the **Length** value specifies a minimum distance between the driving item and the intersection point. If the driving item is located further away from the line than the distance set in this channel, then Modo continues to use the closest distance. However, if the distance is less than the **Length** value, then Modo pushes the intersection along the line to maintain the specified length between the driver and the intersection point. When used with a Plane intersection, Modo determines the direction to push from the positive Z axis of the driving item. See below for an example of each.