“Enamored of the unavoidable materiality of paint, Mr. McAdams creates uncompromising statements of physical fact. But he doesn’t forgo illusion: The images “discovered” during painting—microscopic life forms, dew-covered spider webs and constellations—rescue the work from object-like inertia. Illusion and, with it, metaphor slip in over the transom, whether Mr. McAdams wants them to or not. It’s to his credit that the paintings are allowed to develop on their own terms.