Add note

css-borders-4/Overview.bs

@@ -1586,16 +1586,22 @@ To get the <dfn>border-aligned corner clip-out path</dfn> given a {{DOMPointRead
 		1. Let |v1| be  [=vector between two points|the vector between=] |curveCenter| and |adjustedCornerEnd|, [=two-dimensional vector/scale|scaled by=] |x|.
 		1. Let |v2| be  [=vector between two points|the vector between=] |curveCenter| and |adjustedCornerStart|, [=two-dimensional vector/scale|scaled by=] |y|.
 		1. Return the {{DOMPointReadOnly}} at <code>(|x|, |y|)</code>, [=point extended by vectors|extended by=] « |v1|, |v2| ».
+
 	1. Let |controlPoint| be the result of calling |mapPointToCorner| given |unitVectorFromStartToControlPoint|'s {{DOMPointReadOnly/y}} and <code>1 - |unitVectorFromStartToControlPoint|'s {{DOMPointReadOnly/x}}</code>.
 	1. Let |axisAlignedCornerStart| be the intersection between the lines <code>(|adjustedCornerStart|, |controlPoint|)</code> and <code>(|clipStart|, |clipOuter|)</code>. If the lines are parallel, let it be <code>adjustedCornerStart</code>.
 	1. Let |axisAlignedCornerEnd| be the intersection between the lines <code>(|adjustedCornerEnd|, |controlPoint|)</code> and <code>(|clipEnd|, |clipOuter|)</code>. If the lines are parallel, let it be <code>adjustedCornerEnd</code>.
+
+			Note: |axisAlignedCornerStart| and |axisAlignedCornerEnd| act as "miters" when rendering an outset.
+			They are a straight extension of the curve's tangent, intersecting with the unshaped target rect.
+
 	1. Let |path| be a path, starting at |axisAlignedCornerStart|.
 	1. If |curvature| is -&infin;:
 		1. Extend |path| to |adjustedCornerOuter|.
 	1. Otherwise:
 		1. Let |K| be <code>0.5<sup>-abs(|curvature|)</sup></code>.
 		1. For every |T| between 0 and 1, in an [=implementation-approximated=] manner,
 				extend |path| to the result of calling |mapPointToCorner| given <code>|T|<sup>|K|</sup></code> and <code>(1 - |T|)<sup>|K|</sup></code>.
+
 	1. Extend |path| to |axisAlignedCornerEnd|.
 	1. Extend |path| to |clipOuter|.
 	1. Return |path|.