Perception d'echelle

Notre cerveau utilise plus de 10 indices de profondeur pour estimer les distances et les tailles. En VR, certains indices (parallaxe binoculaire, accommodation) fonctionnent differemment que sur ecran. Resultat : les objets semblent souvent plus petits ou plus proches qu'en realite. Cet atelier visualise la constance de taille et l'impact du FOV sur la perception scalaire.

// Scale Perception in VR
// Demonstrates size constancy and FOV effects

// Size constancy: objects maintain perceived size
// despite changing retinal image size with distance
function updateSizeConstancy(object, distance, fov) {
  // In real perception, we compensate for distance
  // On screen, we lose some depth cues

  const physicalSize = 1.0; // 1 meter cube

  // Angular size on retina decreases with distance:
  // angularSize = 2 * atan(size / (2 * distance))
  const angularDeg = 2 * Math.atan(physicalSize / (2 * distance))
                     * (180 / Math.PI);

  // FOV affects how much of the scene we see
  // Narrow FOV = telephoto = compressed depth
  // Wide FOV = fisheye = exaggerated depth
  camera.fov = fov;
  camera.updateProjectionMatrix();

  // Display info
  info.textContent = `Angular size: ${angularDeg.toFixed(1)}° ` +
    `| FOV: ${fov}° | Perceived scale factor: ` +
    `${(angularDeg / baseFov * distance).toFixed(2)}`;
}

// Depth cues demonstrated:
// 1. Relative size (same objects at different distances)
// 2. Linear perspective (converging lines)
// 3. Texture gradient (grid detail diminishes)
// 4. Atmospheric perspective (fog)
// 5. Occlusion (overlapping objects)