Making the raymarching hit threshold proportional to distance implements view-dependent level-of-detail

Normally the raymarcher stops when distance < ε (a constant world-space threshold). Replacing ε with t × pixelAngle (distance × angular size of one pixel) makes distant objects terminate earlier: a surface feature smaller than one pixel will be skipped. This simultaneously provides anti-aliasing (geometric aliasing is removed when features are sub-pixel) and a speed-up (distant regions require fewer steps). IQ calls it ‘cone tracing’ because the ray footprint expands with distance. The visual result is that distant geometry is naturally smoothed rather than over-detailed.

Examples

if(d < 0.001*t) break; // cone-trace early exit — t increases with distance

Assessment

Explain why cone-trace early termination eliminates sparkling/flickering on high-frequency displaced terrain seen at a distance.