Shape constancy from novel views

Pizlo, Z., & Stevenson, A. K.

Department of Psychological Sciences, Purdue University
West Lafayette IN, 47907-1364
Electronic correspondence should be addressed to:
[Abstract][Browser requirements][Demonstration][Shape Experiment]
 Abstract:  Prior experiments on shape constancy from novel views are inconclusive: some show that shapes of objects can be recognized reliably from novel views, while others show just the opposite.  Our analysis of prior results suggests that shape constancy from novel views is reliable when the object has properties which constrain its shape: the object has volumetric primitives, surfaces, it is symmetrical, it is composed of geons, its contours are planar, its images provide useful topological information about its 3D structure. To test the role of some of these constraints we performed a set of experiments.  Solid shapes (polyhedra) were shown on a computer monitor by means of Kinetic Depth Effect.  Experiment 1 showed that shape constancy can be reliably achieved when a polyhedron is represented by its contours (most of the constraints are present), but not when it is represented by vertices or by a polygonal line connecting the vertices in a random order (all the constraints are absent).  Experiments 2 and 3 tested the role of individual constraints. Results of these experiments show that shape constancy from novel views is reliable when the object has planar contours, and when the shapes of the contours together with topological information about the relations among the contours allow for unique interpretation of the shape.  Symmetry of the object and the topological stability of its image also contribute to shape constancy.

Pizlo, Z. & Stevenson, A. (1999) "Shape constancy from novel views". Perception & Psychophysics 61, 1299-1307.

Browser requirements

This is a fairly simple applet that rotates a 3D wireframe or pixel set. It requires a Java-capable browser.

It works with most Java capable browsers. Successfully tested browsers/applet runners are:

Here is a list of browsers that work, but in a weird way:

Conditions by Experiment

Experiment 1 Experiment 2 Experiment 3
Polyhedron Polyhedron Polyhedron
Vertices Partially non-planar, symmetric Three quadrilaterals
Polygonal line (16 vertices) Planar, asymmetric Three triangles
Color vertices Non-planar, asymmetric Polygonal line (7 vertices)
[Abstract][Browser requirements][Demonstration][Shape Experiment]

Applet by Filip Pizlo; page and algorithms written by:
Filip Pizlo, & Adam Stevenson,