Enzymind Labs

[Placeholder for "Stillanimation" project]

Stillanimation

    Examples and comparison of a cyclic motion illusion. This is directly related to the "Four stroke apparent motion" illusion.

Directional edge contrast motion illusion comparison

One-dimensional

Checkerboard twist

Programs and code

References

 

Directional edge contrast motion illusion comparison

     A comparison of several parameters variations of a simple motion illusion:

The prototype animation: 25 px. diameter circles, 76 x 76 px. frame,  2 px. maximum shift, 1/3 seconds/cycle (3 Hz., 8 frames at ~24 frames/s)
Matlab command:
>> nvolOut = ECC_animation_2x2( flRadius, imDim, flPxShiftMax, 1/3 );

 
The eight frames of the prototype.


  

P0-gray (.vol.gz)	PCW-gray (.vol.gz)	PCCW-gray (.vol.gz)	PA-gray (.vol.gz)

P0-linear (.vol.gz)	PCW-linear (.vol.gz)	PCCW-linear (.vol.gz)	PA-linear (.vol.gz)

>> ECC_animation_2x2( 25, 76, 24, .5 );

	<--90 degree phase offset
		<--45 degree phase offset
			<--30 degree phase offset
P0-3_frame (.vol.gz)	P0-4_frame (.vol.gz)	P0-6_frame (.vol.gz)	P0-9_frame (.vol.gz)	P0-12_frame (.vol.gz)	P0-15_frame (.vol.gz)

P0-24_frame (.vol.gz)	P0-36_frame (.vol.gz)	P0-40_frame (.vol.gz)	P0-45_frame (.vol.gz)	P0-60_frame (.vol.gz)	P0-90_frame (.vol.gz)

The prototype animation: 25 px. diameter circles, 76 x 76 px. frame,  2 px. maximum shift, 1/3 seconds/cycle (3 Hz., 8 frames at ~24 frames/s)
Matlab command:
>> nvolOut = ECC_animation_2x2( flRadius, imDim, flPxShiftMax, 1/3 );

 
The eight frames of the prototype.


  

P0-gray (.vol.gz)	PCW-gray (.vol.gz)	PCCW-gray (.vol.gz)	PA-gray (.vol.gz)

P0-linear (.vol.gz)	PCW-linear (.vol.gz)	PCCW-linear (.vol.gz)	PA-linear (.vol.gz)

>> ECC_animation_2x2( 25, 76, 24, .5 );

	<--90 degree phase offset
		<--45 degree phase offset
			<--30 degree phase offset
P0-3_frame (.vol.gz)	P0-4_frame (.vol.gz)	P0-6_frame (.vol.gz)	P0-9_frame (.vol.gz)	P0-12_frame (.vol.gz)	P0-15_frame (.vol.gz)

P0-24_frame (.vol.gz)	P0-36_frame (.vol.gz)	P0-40_frame (.vol.gz)	P0-45_frame (.vol.gz)	P0-60_frame (.vol.gz)	P0-90_frame (.vol.gz)

P0-linear (.vol.gz)	PCW-linear (.vol.gz)	PCCW-linear (.vol.gz)	PA-linear (.vol.gz)

  

[To Do: One-dimensional]

[To Do:

Plot a parameterized 1-D profile at several phases:

Write MATLAB  programs

EC_radial.m

-> edge_contrast_1D_animation.m

-> edge_contrast_1D.m

that generates a phased cyclic sequence of edge contrast vectors.

Test assembling an edge with variable width (and/or phase), angular frequency.

Build the edge necessary for the pinwheel tesselation:

 

Checkerboard twist

2008-11-12 

    While writing the one-dimensional code (for a pinwheel "wedge" edge, EC_radial.m), this high symmetry "cone" structure came up. Do it exactly right, square tiling with no gap, smooth square-profile "teeth" and best continuity. Animated tiling.

2008-11-15 

    Got them roughly alligned, mostly by trial and minimizing error. The geometry of the angles is opaque to me. I'll add the mirror in background, with some artificial fade with depth.

 

A puzzle: The figure below is an arrangement of eight triangles, using three different triangular motifs (say a, b and c) along with a pi/2 rotation of each of the three (say -a, -b and -c). What is the spatial arrangement of the six?

  

     -c        

-b   c    -b

a   -a    a

      b

See Mixed symmetries for details and code.

 

Programs and code

 

    The example frames and volumes for the Directional edge contrast motion illusion comparison were generated by the following MATLAB programs. The GIF animations were assembled from the serial frames using Jasc Software's Animation Shop. Parameter variations are made by both the program arguments and hardcoded items (see header comments for details).

    Space Software was used  to review the animations (utilizing the optional Matlab program output in volume format [.vol] ) and to generate serially numbered 2-D frames (File | Save As Serial Images)

 

References

Visual dissociations of movement, position, and stereo depth: Some phenomenal phenomena

Richard L. Gregory and Priscilla F. Heard
Quarterly Journal of Experimental Psychology (1983) 35A, 217-237
Brain and Perception Laboratory, University of Bristol, Department of Anatomy, The Medical School, University Walk, Bristol BS8 1TD, England

Second-order processing of four-stroke apparent motion

Mather G, Murdoch L

School of Biology, University of Sussex, UK. georgem@biols.susx.ac.uk

Vision Res. 1999 May;39(10):1795-802

"In four-stroke apparent motion displays, pattern elements oscillate between two adjacent positions and synchronously reverse in contrast, but appear to move unidirectionally. For example, if rightward shifts preserve contrast but leftward shifts reverse contrast, consistent rightward motion is seen. In conventional first-order displays, elements reverse in luminance contrast (e.g. light elements become dark, and vice-versa). The resulting perception can be explained by responses in elementary motion detectors turned to spatio-temporal orientation. Second-order motion displays contain texture-defined elements, and there is some evidence that they excite second-order motion detectors that extract spatio-temporal orientation following the application of a non-linear 'texture-grabbing' transform by the visual system. We generated a variety of second-order four-stroke displays, containing texture-contrast reversals instead of luminance contrast reversals, and used their effectiveness as a diagnostic test for the presence of various forms of non-linear transform in the second-order motion system. Displays containing only forward or only reversed phi motion sequences were also tested. Displays defined by variation in luminance, contrast, orientation, and size were effective. Displays defined by variation in motion, dynamism, and stereo were partially or wholly ineffective. Results obtained with contrast-reversing and four-stroke displays indicate that only relatively simple non-linear transforms (involving spatial filtering and rectification) are available during second-order energy-based motion analysis."

 

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