Hi there - can someone help me?

I’m writing a small 3D viewer which, in addition to the triangle mesh of a loaded model, also draws the facet and vertex normals as little lines. Eventually, you will be able to edit the vertex normals to tweak the shading in low-poly models.

The lengths of the facet normals should be proportional to the ‘size’ of the actual triangle - ie. not it’s 2D projected size. So I need a way to (quickly) calculate the area of the triangle.

Now I know who to calculate the area of a 2D triangle: (H x w)/2. But how can I calculate the area of a triangle defined by three 3D points? It’s still a planar triangle, but in 3D space.

Ideally, this would just be a float that I would multiply the vector normal with