# Area of a mesh face in C# in Grasshopper

|Another quick script for handing meshes – this time to find the area of a mesh face.

This script is in C# and can be easily used with the C# component in Grasshopper. Copy the script into the ‘custom additional code’ section. It is written as a method, so you can easily call it. In the ‘RunScript’ section, call the method with something like:

double area = Area(3, myMesh)

This will return the area of the third face in the mesh called myMesh.

The method itself to calculate the area of a mesh face is below. Of course, you can use this method in any C# application, not just Grasshopper – you’ll just need to modify the code to fit whatever data structure your mesh uses.

double Area(int meshfaceindex, Mesh m) { //get points into a nice, concise format Point3d[] pts = new Point3d[4]; pts[0] = m.Vertices[m.Faces[meshfaceindex].A]; pts[1] = m.Vertices[m.Faces[meshfaceindex].B]; pts[2] = m.Vertices[m.Faces[meshfaceindex].C]; if(m.Faces[meshfaceindex].IsQuad) pts[3] = m.Vertices[m.Faces[meshfaceindex].D]; //calculate areas of triangles double a = pts[0].DistanceTo(pts[1]); double b = pts[1].DistanceTo(pts[2]); double c = pts[2].DistanceTo(pts[0]); double p = 0.5 * (a + b + c); double area1 = Math.Sqrt(p * (p - a) * (p - b) * (p - c)); //if quad, calc area of second triangle double area2 = 0; if(m.Faces[meshfaceindex].IsQuad) { a = pts[0].DistanceTo(pts[2]); b = pts[2].DistanceTo(pts[3]); c = pts[3].DistanceTo(pts[0]); p = 0.5 * (a + b + c); area2 = Math.Sqrt(p * (p - a) * (p - b) * (p - c)); } return area1 + area2; }

This script is based upon Heron’s Formula, which calculates the area of a triangle based upon knowing its three lengths. The script also calculates the area for quads. It does this by dividing the quad into two triangles.