Investigating the effect of texture orientation on shape perception

We are interested in investigating the effect of texture orientation on shape perception, with the goal of determining how to use texture to enhance the representation of surface shape for visualization applications. To this end we have developed an efficient algorithm for synthesizing a high resolution texture pattern (given by a 2D sample image) over an arbitrary polygonal surface in such a way that the orientation of the texture follows a specified vector field at a per-pixel level. We are in the process of conducting a series of experiments to evaluate the effects of various texture conditions on various kinds of shape judgements.

Texture orientation follows a constant "up" direction

Texture orientation follows the direction of greatest normal curvature

Texture orientation follows the direction of least normal curvature

Left: texture orientation follows the direction of least normal curvature
Right: texture orientation follows a constant "up" direction

These are examples of some of the sample textures and textured surfaces that we have used in our latest experiments investigating the effect of various texture characteristics on shape perception. The task for the observer is to indicate the surface normal direction using a Koenderink-style probe (not shown in these images).

From left to right: two-directional line texture, one-directional line texture, one-directional lic texture samples.

A surface with the two-directional line texture, oriented to follow both of the principal directions.

The same surface with the one-directional line texture, oriented to follow the first principal direction only. Notice the abrupt pattern discontinuities that occur where the first and second principal directions "switch places".

The same surface with the one-directional lic texture, oriented to follow the first principal direction only. Texture discontinuities appear less prominent with this more complex pattern.

The same surface without any texture.

We are currently running studies that look at the effect of global vs local information (using a window to hide global information), the effect of perspective vs orthographic projection, and the effect of using ceiling vs ground plane based surfaces.

Here are some pictures from an earlier experiment, in which we used textures synthesized via line integral convolution. These textures were very easy to create but they have the disadvantage that they can only represent one of the two principal directions at a time. The paper (presented at Human Vision and Electronic Imaging VI) is available here.

Texture orientation follows a vector field of random directions

Texture orientation follows a vector field of uniform (constant) directions

Texture orientation follows a vector field of coherently varying directions

Texture orientation follows a vector field of first principal directions

Poster presented at Vision Sciences Society meeting 2002