Considering the problem of shape/painting as opposed to form/sculpture, and how difficult it is not to unwittingly refer Plato's allegories where the world of sense perceptions is inferior to the world of Ideal entities, those that exist only in a purely spiritual/conceptual realm. Just the other-day was thinking about how even an abstract painting-color-field can posses a semblance of beauty that would be impossible if that same flat-painting were to be made into real-form (even a simple cylinder would radically alter how it was seen). If that were the case the painting would suddenly appear as something else, it would become decoration on something, rather than a painting about something.
It therefore seems to follow that we recognize form with a different set of criteria -possibly due to parallax-than we do with shapes/colors. [Once again Plato has reversed the real order of the world so that the mind's eye of vita contemplation is the highest order/goal.] Real things --reality--are viewed 3-dimensionally, either by walking around or by different people's different viewpoints which generate consensus. Men exist in The Real/Round/Reality and men/individuals, while not the measure of all things are certainly the measurers, therefore, all scale's marked through it's recognition related to the viewer, not against an ideal. The challange -in an age & society which has lost visual perspective- is to arrest the viewer into presentness with form, rather than through the sublimity of hues and illusions.
While reading/ re-reading The Republic (10th chapter) wherein he argues for The Ideal -in his usual Socratic method (which denigrates without an opportunity to respond)-felt a rebuttal was necessary, even if incomplete. In Plato's argument there's so many assumptions later used by The Church to validate a antimaterialistic ephemeral/eternal spirituality, that to confront them seems to contradict modern ideology by pointing out that reality is of a higher order than mere ideals and, more importantly, it pertains to individuals rather than to mankind. Individual actions create history; (it's not preordained as theologians, Marxists and American Neo-Hegalians assume) and to deny that fact is to live in the future, meaning that the present losses it's relative stability/force. Actually, to live in either the past or the future is flat/painterly, 2-dimensional, a concept/shape without form, without definition... like an ad, it's a generality without details.
Plato uses the word Form to construct a concept rather than a reality -as a method to denigrate the senses-therefore language persists in this confusion. Part of what's necessary is a modification/rectification of the aesthetic vocabulary, no mean task. I suppose all i want to is make the statement as i've never read a refutation of this aboriginal argument (that beauty lies beyond perception, that the closer to illusion something is the more real it becomes, that sculpture is inferior to painting). This Ideal/idea, because it fits so well into the modern sensibilities of a constantly improving future, makes progress inevitalbe; a forward march at the expense of the present, at the expense of the Real. This Ideal is a tyranny of the Formless, a shadow of the mind.
(Footnote /Reference) Plato, 'The Relation of Art to Truth', Book X of The Republic.