Depth Cues

In the field of vision and perception sciences, depth refers to the distance and position of objects we perceive in three-dimensional space. Even when viewed through a two-dimensional medium, such as pictures or screen, we are still able to perceive the three-dimensional nature and depth of these objects using a variety of visual cues. These visual cues are also known as depth cues.

Categorization of depth cues

The following shows the categorization of depth cues, but it is not the only categorization standard.

Please move your mouse over the rectangles with different depth cues to see the details.

// update 13.06.2024 Lingyu Tang

Relative and absolute sizes of objects can provide depth information.

Depth information can be derived from the use of a single eye.

Depth information can be derived from the use of both eyes.

Distant objects appear blurrier and lighter in color due to atmospheric scattering and absorption of light.

Objects are usually considered to be further away when their position is close to the horizon.

To focus on close objects, both eyes need to be turned inward. The greater the angle of rotation, the closer the object.

When an object partially occludes another object, the occluding object is perceived as closer and the occluded object as more distant. This cue depends on the relative spatial position between the objects.

Texture details on the surface of an object become progressively blurred and denser with distance.

The shading and variations in light and darkness produced by light on the surface of an object provide information about the shape and relative position of the object. The direction and length of shadows can reveal the three-dimensional structure of the object and the location of the light source.

When an observer moves, near objects move faster in the field of view than distant objects.

The lens of the eye adjusts its curvature to focus on objects according to their distance.

In the visual field, parallel lines appear to converge at a point in the distance, the vanishing point. As distance increases, the relative size and spacing of objects visually decreases.

The edges of an object curve near the edge of the field of view, and this curvature can reflect curved structures in three dimensions on a two-dimensional plane.

Because the two eyes are positioned differently, they receive images with small differences, and this binocular parallax is processed by the brain's stereo vision to provide accurate depth perception. The greater the parallax, the closer the objects are.

 Depth cuesMonocular Binocular StaticDynamicOculomotor Linear perspective PerspectiveShading and shadows Size Occlusion Texture gradient Motion parallax Accommodation Curvilinear perspective Aerial perspective Horizon elevation Convergence Disparity

Hands-On

Left-click on the cube and long press, you can drag it left, right, up and down, it will not change the depth.

Right-click on the cube to display its details.

Click on "Light Setting" to modify the position and size of the light source and the shadows.

Click on "Reset", the light, gridlines and planes will be restored to its default value and the depth of the cubes will be reset randomly.

The important coordinates:
Origin: (0, 0, 0).The horizontal direction is the x-axis, the vertical direction is the y-axis, and the depth direction is the z-axis.
Camera: (20, 5, 20). The screen shows the scene from the camera's perspective
Light source: (15, 40, 20).The light shines on the cubes and casts shadows on the plane.

References