I am new too Maya and I am making a gas usage box on a building and I want to make a circle on my extruded rectangle in order to make the valve. I am not sure how to make circles on faces. I am not even sure if this is possible in Maya, I know it is possible in other programs, such as Blender, which I have used before. Thank you in advance for the help.
You could use a Boolean Difference between the face of the cube and a cylinder. This will give you the geometry needed. Once you perform the difference simply select the new faces then move pull them out of the cube. You must be careful when using booleans though as they create non manifold geometry. After performing the difference you must reselect the original face and either perform a triangulation or manually connect the new vertices with the ones already existing on the cube. Once you try it out you will see what I mean. Hope this helps and good luck
Thank you very much. While I do not know what "manifold geometry" or a "triangulation" is, after playing around with Boolean Union, Difference, and Intersection, I found that I could simply put the cylinder inside the cube and perform the Boolean Union, which would combine the two objects and also remove the excess geometry of the cylinder that came through into the cube.
Ok once you do the Boolean difference you need to fix up the geometry. Basically the face of a cube has 4 vertices and 4 edges. The cylinder that you have done the difference with may have up to 20 vertices and edges. You now have to connect the 20 vertices to the original 4 outer vertices of the cube so that the geometry will be displayed and rendered correctly. If you were to take this object into another program or game engine it would not look correct as it will try to solve itself and create overlapping faces which will flicker as you move around the scene.
If you select the original face of the cube, when you enable face selection (hold down right mouse button and select face) you should still be able to select the original face. With this face selected select Mesh > Triangulate. This will correct all of the geometry. This is not the best method of doing this but it is definitely the simplest. Once you do this you will see what I mean. If you wanted more control over the finished geometry you could use the Split Polygon tool located under the Edit Mesh menu.