Shrinker wrote:I found a really cheap way of making an arc today:

You basically make a piece which is 2 units high, and add a 45° slope at one end, then just copypaste it, and along one axis, double its size each time

Note that this is not an x² parabola, and probably no c*x² (c <> 1) parabola either.
Regarding the arches, I'm not sure if you know this or not, but the proper way to do a arc in hammer is like this:

Although hammer does must of the job for us, the "geometric" method for creating this type or arches is this:
1- Create half a square (for a 45º arc) with the desired size (in this case 128x128)

2- Divide each side of the square in equal parts. The number of divisions is equal to the number of sides you want the arch to have (in this case 4)

3- Connect each point to the corresponding point on the opposite side like this




4- You now have all the points that define the "arc", and you just have to create the triangles (source works better with triangles) like this






The reason I'm posting this, is that it would be great if the program could create the geometry in an engine friendly way. In the example of the arches you could just create a box, select in which axis you want the arc to be, the number of sides, and degrees, and it would create a arc like this.