Shade, Sheen and Feather

Shade went first, because roundness is impossible to depict without a vocabulary of values — and the ramp is that vocabulary.

"Here is the ramp," Shade said, setting out a run of grays: a deep dark, a low mid, a high mid, a near-white — a small, evenly-spaced set from shadow to highlight. "The discipline is restraint. You do not want dozens of steps; you want a handful, spaced evenly, with the dark dark enough and the light light enough to carry the whole range." Shade held the strip level. "One flat colour asserts flatness and nothing else. A ramp is the raw material of form, because a curved surface is darker where it turns away from the light and lighter where it faces it. I am not placing anything yet — placement is Sheen's decision. I am only building the palette the illusion will be spoken in. Get the ramp evenly spaced and correctly anchored, and the foundation is laid; everything after is knowing where each value belongs."

Then Sheen committed to a light source, and the flat disc resolved into a sphere — because form-shading is, at bottom, obedience to a single decision about where the light lives.

"Now the part that feels like magic but is really just consistency," Sheen said. "I choose where the light originates — up and to the left, an afternoon sun — and then every value answers to that one choice." Sheen placed the ramp accordingly: the lightest value where the imagined light struck the upper-left, the mid-values wrapping around the turn of the form, the darkest value pooling in the lower-right where the surface curved into shadow, and a single near-white specular dot at the point of brightest gleam. The flat gray circle stopped asserting flatness. It rounded — became a sphere, solid and sitting in real light, on a grid of nothing but squares. "That is the whole of it," Sheen said. "Pick the direction, commit, and then place bright where the light reaches and dark where it cannot. The non-negotiable is consistency — the entire picture must obey the same sun. Decide once, shade everything to match, and flat squares acquire volume in front of you."

And then Feather stepped in for the finishing pass — resolving the harsh, stair-stepped diagonals with a few precisely-placed in-between pixels.

"Look at the silhouette where the curve runs diagonal," Feather said. "The grid forces the edge into a staircase — hard corners that announce the squares." Feather leaned close. "So into each stair-step corner I set a pixel of an intermediate value — a shade sitting halfway between the sphere's edge and the background behind it." Feather tucked the transitional pixels into the jagged notches, and no more. "Now, from an ordinary viewing distance, the eye integrates them: the staircase reads as a smooth arc. That is anti-aliasing — a sparing set of transitional pixels that let the eye perceive a continuous edge where the grid can only build a discrete one." Feather stepped back. "It is the smallest intervention of the three — a few pixels — and it is precisely what separates a rough sprite from a finished one. The eye stops registering individual squares. It registers a smooth, solid, rounded form, and never suspects the grid underneath."