Bend Lines Illusion
Method 1: My first approach lends itself easily to proceduralism and the copy node.
With
the use of a circle, line and copy node this is resolved
quickly. However if you look at the source it is not quite
accurate. In fact, in the original image the angles subtended
by the lines are not equal and the lines are not symmetric.
For example on the upper right quadrant between the horizontal
and vertical reference lines are 6 lines, on the left only 5.
Similarly in the lower quadrants. Method 2: was to use if statements in hscript to add these variations which works well. Pictured below left is the version from Method 2 and below right is the render superimposed on the original image.
However, I wanted to replace the clunky if statements I used
in hscript with elegant vex expressions. This lead me to the
question of how can I easily create the lines artistically? It
would be handy to just poke on a point and have the
application take care of drawing the line from the center to
the point - thus groups and add nodes were used (see Spokes
wrangle example). Method 3:
- drawing a curve
- deleting all but the points (add)
- then grouping the origin with each point (pointwrangle)
- adjusting the size of the line (pointwrangle)
Now that you have the overview, let's step thru it for beginning Houdini users.
Method 1 and 2 can be found in
Example opticalBend.hipnc
(if you want to use the image in the camera download BendLineCenter.PNG)
Method 2 uses a collection of if statements in each
quadrant. It works, but a more elegant solution can be seen
in Method 3 with a point wrangle node.
Method 3: In the file
Example spokesBendLine.hipnc
(images is BendLine.PNG
to see original texture) the approach described above was
used by drawing a curve, deleting all but the points,
grouping the origin with each point and adjusting the size
of the line (with pointwrangles of course).
In this case the image was projected onto a grid (we could
have used it as a background camera image but this allows
easy adjustment to center the image).
In this method, it is similar the previous two, however it
allows us to quickly add the connecting points
- BrainDen.com and in particular line illusions.
- http://www.psy.ritsumei.ac.jp/~akitaoka/index-e.html (website of Akiyoshi Kitaoka, Professor, Department of Psychology, Ritsumeikan University, Kyoto, Japan)
- google optical illusions