Hard color boundaries read as spatial separation; soft boundaries signal proximity or penetration

When two colors meet at a boundary, the sharpness of that edge carries spatial meaning. A hard (high-contrast) boundary pushes the two colors apart in perceived depth: one reads ‘in front,’ the other ‘behind.’ A soft boundary (reduced contrast in either hue or lightness at the edge) suggests the areas are at the same depth plane or interpenetrate. A middle mixture — precisely equidistant from both parents — produces equally soft edges on both sides and reads as frontal/flat (neither advances nor recedes). Albers credits Cézanne as the first to deploy this deliberately: mixing areas with clear and indistinct endings to create spatial modulation without linear perspective.

Examples

In Hydra: sharp edge between contrasting colors reads as two planes; smooth gradient edge reads as coplanar. In GLSL: step() at an SDF boundary gives hard depth separation; smoothstep() with wide range creates interpenetration.

Assessment

Create three color studies: all hard boundaries, all soft boundaries, mixed. Describe the spatial reading of each. Identify which boundary principle Cézanne exploited and why it contradicts traditional perspective-based depth cues.