diff --git a/todo.txt b/todo.txt
index 1e51fc5..53cadf4 100644
--- a/todo.txt
+++ b/todo.txt
@@ -64,6 +64,14 @@ bugs:
 - Determining CW/CCW for a triangle is not 100% exact, sometimes leaves holes in
   models (some very thin triangles)!
 
+- With PC = 2, triangles that are at a too sharp angle can get very weird values
+  of barycentric AND DEPTH (which messes up the z-buffer). Seems to only affect
+  triangles facing right (not left).
+
+- Barycentric coodinates can get wrong in these ways:
+  - Any of them can exceed the range <0,511>
+  - b0 + b1 can be > 511, which causes b2 (= 511 - b0 - b1) to be negative!
+
 repeated:
 
 - valgrind (and similar) checks