There are 4 ways of moving a motif to another position in the pattern. He adopted a highly mathematical approach with a systematic study using a notation which he invented himself. There are 17 possible ways that a pattern can be used to tile a flat surface or 'wallpaper'.Įscher read Pólya's 1924 paper on plane symmetry groups.Escher understood the 17 plane symmetry groups described in the mathematician Pólya's paper, even though he didn't understand the abstract concept of the groups discussed in the paper.īetween 19 Escher produced 43 colored drawings with a wide variety of symmetry types while working on possible periodic tilings. One mathematical idea that can be emphasized through tessellations is symmetry. If you look at a completed tessellation, you will see the original motif repeats in a pattern. The term has become more specialised and is often used to refer to pictures or tiles, mostly in the form of animals and other life forms, which cover the surface of a plane in a symmetrical way without overlapping or leaving gaps. They were used to make up 'tessellata' - the mosaic pictures forming floors and tilings in Roman buildings The word 'tessera' in latin means a small stone cube. When you fit individual tiles together with no gaps or overlaps to fill a flat space like a ceiling, wall, or floor, you have a tiling. Return to more free geometry help or visit t he Grade A homepage.A tessellation is created when a shape is repeated over and over again covering a plane without any gaps or overlaps.Īnother word for a tessellation is a tiling. Return to the top of basic transformation geometry. This is typically known as skewing or distorting the image. In a non-rigid transformation, the shape and size of the image are altered. You just learned about three rigid transformations: This type of transformation is often called coordinate geometry because of its connection back to the coordinate plane. Rotation 180° around the origin: T( x, y) = (- x, - y) In the example above, for a 180° rotation, the formula is: Some geometry lessons will connect back to algebra by describing the formula causing the translation. That's what makes the rotation a rotation of 90°. Also all the colored lines form 90° angles. Notice that all of the colored lines are the same distance from the center or rotation than than are from the point. The figure shown at the right is a rotation of 90° rotated around the center of rotation. Also, rotations are done counterclockwise! You can rotate your object at any degree measure, but 90° and 180° are two of the most common. Reflection over line y = x: T( x, y) = ( y, x)Ī rotation is a transformation that is performed by "spinning" the object around a fixed point known as the center of rotation. Reflection over y-axis: T(x, y) = (- x, y) Reflection over x-axis: T( x, y) = ( x, - y) In other words, the line of reflection is directly in the middle of both points.Įxamples of transformation geometry in the coordinate plane. The line of reflection is equidistant from both red points, blue points, and green points. Notice the colored vertices for each of the triangles. Let's look at two very common reflections: a horizontal reflection and a vertical reflection. The transformation for this example would be T( x, y) = ( x+5, y+3).Ī reflection is a "flip" of an object over a line. More advanced transformation geometry is done on the coordinate plane. In this case, the rule is "5 to the right and 3 up." You can also translate a pre-image to the left, down, or any combination of two of the four directions. The formal definition of a translation is "every point of the pre-image is moved the same distance in the same direction to form the image." Take a look at the picture below for some clarification.Įach translation follows a rule. The most basic transformation is the translation. Translations - Each Point is Moved the Same Way The original figure is called the pre-image the new (copied) picture is called the image of the transformation.Ī rigid transformation is one in which the pre-image and the image both have the exact same size and shape.
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