When two or more adjectives each modify a noun separately, they are coordinate.

If the adjectives can be joined with and, the adjectives are coordinate, so you should use commas: warm and gentle and affectionate (warm, gentle, affectionate).

Adjectives that do not modify the noun separately are cumulative.

Beginning with the adjective closest to the noun shapes, these modifiers lean on one another, piggyback style, with each modifying a larger word group. Gray modifies shapes, large modifies gray shapes, and three modifies large gray shapes. Cumulative adjectives cannot be joined with and (not three and large and gray shapes).

coordinate adjectives

Adjectives are coordinate if they can be connected with and: severe and irreversible.

cumulative adjectives

Ira didn’t order a cake that was rich and chocolate and layer. He ordered a layer cake that was chocolate, a chocolate layer cake that was rich.