Ian Badcoe<p><a href="https://peoplemaking.games/tags/GameDev" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>GameDev</span></a> <a href="https://peoplemaking.games/tags/ComputerGraphics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>ComputerGraphics</span></a> <a href="https://peoplemaking.games/tags/Normals" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Normals</span></a> <a href="https://peoplemaking.games/tags/Meshes" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Meshes</span></a> I am already well familiar with the concepts of vertex and face normals, and I know ways to calculate them for simple, or even quite complex cases. Simple being all smooth, or all facetted. Moderately complex being where we have some sharp and some smooth edges, maybe based on an angular threshold, and can share or split verts/normals accordingly.</p><p>But... but... what do we do when the mix of sharp and smooth edges is ambiguous, like in the picture. The red edge is sharp and the three blue ones are smooth, so how do we treat the 4 polygons where they meet at the vertex? There is no clean division between polys which connect smoothly and ones which should be separate rotating anticlockwise from A to D, all the edges should be smooth, so A should share a normal with B, and thus with C and eventually D, but going the other way, from A straight to D, we'd like the line to be sharp and we'd like them not to share. Obviously we can't have both. It's a puzzler...</p>