Update README.md

README.md

@@ -1,2 +1,41 @@
 # ProfileToolBox
-ProfileToolBox reverse engineered Civil 3D to implement creation of profiles from polylines
+ProfileToolBox: tool to create Autodesk Civil 3D profiles in a profile view based on a polyline.
+![](demo.gif)
+
+I needed to draw profiles in profile views in Civil 3D based on a polyline and I found the ProfileToolBox tool at: https://forums.autodesk.com/t5/civil-3d-forum/profile-from-polyline/m-p/6012180/highlight/true#M293493 but it didn't work!
+
+So, today, I got the idea to decompile it and try to figure out what goes wrong. I already had some Revit API programming experience, but no Autocad experience, so it was fun to try. Also, I hope I don't violate any copyright laws by doing this this way -- I do not know the original creator of this tool, so I cannot ask in advance!
+
+I found two problems in the code, which I think fixed the tool:
+
+Problem 1:
+The tool was creating a new profile, but it didn't contain any visible geometry. I think this was because the newly created profile wasn't opened for writing -- hence the change.
+Original:
+
+```c#
+Profile profile = tx.GetObject(profByLayout, OpenMode.ForOpen) as Profile;
+```
+
+Changed to:
+
+```c#
+Profile profile = tx.GetObject(profByLayout, OpenMode.ForWrite) as Profile;
+```
+
+Problem 2:
+There is a section in the code, which tries to get the mid point of a polyline arc, but it was doing it with 10 points choosing 6th point -- which isn't the mid point. I changed it to 11 points choosing 5th point -- remember, the index of points is zero-based -- this gives the correct midpoint.
+Original:
+
+```c#
+Point2d samplePoint = ((Curve2d)arcSegment2dAt).GetSamplePoints(10)[6];
+```
+
+Changed to:
+
+```c#
+Point2d samplePoint = ((Curve2d)arcSegment2dAt).GetSamplePoints(11)[5];
+```
+
+The tool worked on first compile after that, see gif for proof. ;)
+
+To get it to work, download the compiled .dll here or compile it your self in VisualStudio and use 'netload' in acad to load the tool. Then call command: 'mypfp' to start the profile creation process.