If you say that the intellect forms a mental picture of something seen by the soul in some physical form (e.g. an actual circle), it is not so. What the soul sees are the powers of the spiritual realm arranged in a certain order that is expressed in the form in which the soul sees them. (For example, the soul may have a perception of God’s overall, general providence – as opposed to His individual providence over the details of creation – and “translate” this perception into the form of a “circle”.)
Thus the Sefirot are seen as lights arranged in a spiritual order which is understood as having the form of circles (igulim) or as having a straight, upright form (yosher). The Sefirot may “break through” or “ascend” or “descend” in various ways. Not that this is the actual form it takes, but this is how we can understand it.