Triangles, polygons, and circles are all considered two‐dimensional objects and you’ve learned how to find the perimeter and area of these objects. You will also need to know how to analyze the measurements of their three‐dimensional counterparts, or solid geometry. For solid geometry, you will need to know the volume and the surface area of a three‐dimensional object. The surface area of a solid figure is like the perimeter of a two‐dimensional object. The volume of a solid figure is like the area of a two‐dimensional object.