Point List Normal

Description

This node takes multiple vectors representing the points of a polygon and computes the normal of that polygon. At least 3 points are needed to compute the normal. If more than 3 noncoplanar points were input, the computed normal will be the average of the normals of each 3 points. If the points are collinear, the node will return a zero vector because no norml can be computed.

../../../_images/point_list_normal_node.png

Inputs

  • Point List - A vector list that contain the locations of the polygon’s points.

Outputs

  • Normal - A unit vector representing the normal of the polygon. A zero vector if points weren’t valid, that is, collinear.
  • Is Valid - A boolean which is True if the points are not collinear and False otherwise.

Advanced Node Settings

  • N/A

Notes

The order of points matter, because the cross product is used to compute the normals. So, reversing the order of points reverse the direction of the normal.

Examples of Usage

The normal of a triangle formed from three points is computed using the Point List Normal node, this normal, in turn, is used to orient a cylinder such that its principal axis aligns with the normal of the triangle. Moreover, the cylinder is positioned in the center of the triangle, which is computed by taking the average of the points.

../../../_images/point_list_normal_node_example.gif

The polygon normals output of the Mesh Object Input node is identical to the normals computed using the Point List Normal node.

../../../_images/point_list_normal_node_example.png