SKILL TREE

Have from CAD: nothing — pure motor skill. Lack: all of it. The bottleneck for every tier above.

• Grip & motion source — shoulder/elbow vs wrist, matched to mark sizeStep 01
• Straight lines — ghosted, one committed pass needs: gripStep 01
• Arcs & curves — same ghosting, smooth needs: grip
• Ellipses — ghosted, drawn through, honest minor axis needs: arcsStep 02
• Line-weight control — deliberate heavy vs light in one pass needs: straight linesStep 02

Exit — confident committed lines and passable freehand ellipses without a straightedge. Unlocks T1 and T2.

Have from CAD: little — CAD is 100% constructive. Lack: seeing by eye. The anti-CAD-brain tier: suspend the urge to construct and measure.

• Contour (blind → modified) — draw by sight, eye on subject needs: T0 gripStep 03
• Comparative proportion — unit + sighting, by eye not ruler needs: T0 gripStep 03
• Negative space — draw the gaps to correct the object needs: contour
• Gesture — capture the whole/movement fast, before detail needs: T0 grip

Exit — proportions judged by eye land close; a contour reads as observed, not invented. Feeds T3.

Have from CAD: the whole mental model. Lack: only freehand execution and line convergence. Framed in CAD vocabulary — don't re-learn 3D.

• 1pt / 2pt perspective — VPs, horizon, convergence by hand needs: T0 straight lines
• The box in space (250-box) — freehand convergence reps needs: perspective
• Primitives from any angle — box, cylinder, sphere (= sketch-plane + extrude/revolve) needs: box, T0 ellipses
• Ellipses-on-forms — cylinders, wheels, bores; degree shifts with view needs: T0 ellipses + perspective
• Form intersection / boolean — combine primitives, draw the seam needs: primitives
• Symmetry across perspective — mirror a form convincingly needs: primitives

Exit — invent a simple multi-part object in correct perspective, freehand, no ruler. Feeds T3.

Have from CAD: reading curvature and light — zebra, curvature comb, shaded previews. Lack: putting it down by hand.

• Cross-contour lines — lines wrapping the surface (= isolines by hand) needs: T1 contour + T2 primitives
• Planar analysis — break a form into flat planes; bridge to hatching needs: T2 primitives
• Form shadow vs cast shadow — terminator, core, cast needs: planar analysis

Exit — show volume with cross-contours; place core and cast shadow correctly. Unlocks T4.

Have from CAD: intuition for where shadow falls. Lack: the manual mark systems — and the restraint to hatch selectively. needs: T3 form/shadow + T0 line-weight

• Single hatch → cross-hatch — even, controlled parallel sets
• Form-following (curved) hatch — rides the cross-contours needs: T3 cross-contour
• Selective placement — core + cast shadow and accents only, not everywhere
• Value via density — light/mid/dark by spacing, not pressure alone
• Texture — bark, stone, matte vs gloss metal via mark character

Exit — a form reads solid and lit from a few well-placed hatch passes; most of the paper stays line and white.

• Natural form, line + selective hatch, from life — closes the observational track
• Invented product, constructed → rendered, from imagination — closes the constructive track
• Line-weight hierarchy — heavy contour, lighter interior needs: T0 line-weight
• Memory-drawing loop — draw a studied subject from memory; test retention