The illustration of a cube with filleted corners follows specific rules. Therefore, you must account for certain considerations when you depict such a cube. Get to know more about these filleted corners and learn how to build such a cube correctly.

The so-called filleted corners emerge when all the corners of a cube are rounded off. This is accomplished by rounding all the abutting edges off, too. Three of these curves always converge in the corners of the cube and result in a filleted corner.

If you wish to illustrate a cube with filleted corners, you should start with an ordinary cube.

Using the three standard ellipses of the applied grid, you then draw a spherical body. The diameter of all the ellipses should be double the rounding radius. The center of each ellipse must be on the exact same spot. Draw a circle around all the ellipses.

This spherical body can now be used to depict the filleted corners of the rounded off cube. You can delete redundant lines later. Beginning with the upper left corner, you align the center of the spherical body and move it along the edges. You choose the value of the radius as the distance.

Three movements create a primary direction and a specific distance at each corner. This distance equals the ellipses' diameter, i.e. it doubles the rounding radius. The respective main directions are depicted in the diagram below. One exception is the spherical body in the center: Here, all the movements are offset and its center rests on the corner.

You can now delete the basic cube. You will not need it any longer. However if you need to consider other dimensions, you should not delete it yet. You will need the corners of the basic cube as reference points. Now, connect the ellipses and circles with tangents, as shown in the following illustration.

         
    
Finally, delete all redundant lines of the ellipses and your perfectly rounded cube is finished. Please keep in mind that a cube with filleted corners always looks a little bit smaller than a non-rounded cube.