人机接口与图形学(双语)05-Polygon Clipping.ppt

Content Line Clipping Polygon Clipping Clipping Polygons Clipping polygons is more complex than clipping the individual lines Input: polygon Output: original polygon, new polygon, or nothing When can we trivially accept/reject a polygon as opposed to the line segments that make up the polygon? What happens to a triangle during clipping? Possible outcomes: triangle ? triangle Why Is Clipping Hard? triangle ? quad triangle ? 5-gon How many sides can a clipped triangle have? How many sides? Seven… A really tough case: Why Is Clipping Hard? A really tough case: Why Is Clipping Hard? concave polygon ? multiple polygons Sutherland-Hodgeman Clipping Basic idea: Consider each edge of the viewport individually Clip the polygon against the viewport edge’s equation Sutherland-Hodgeman Clipping Basic idea: Consider each edge of the viewport individually Clip the polygon against the edge equation After doing all edges, the polygon is fully clipped Sutherland-Hodgeman Clipping Basic idea: Consider each edge of the viewport individually Clip the polygon against the edge equation After doing all edges, the polygon is fully clipped Sutherland-Hodgeman Clipping Basic idea: Consider each edge of the viewport individually Clip the polygon against the edge equation After doing all edges, the polygon is fully clipped Sutherland-Hodgeman Clipping Basic idea: Consider each edge of the viewport individually Clip the polygon against the edge equation After doing all edges, the polygon is fully clipped Sutherland-Hodgeman Clipping Basic idea: Consider each edge of the viewport individually Clip the polygon against the edge equation After doing all edges, the polygon is fully clipped Sutherland-Hodgeman Clipping Basic idea: Consider each edge of the viewport individually Clip the polygon against the edge equation After doing all edges, the polygon is fully clipped Sutherland-Hodgeman Clipping Basic idea: Consider each edge of the viewport individually Clip the polygon against the edge equati