Thank you. That is really fantastic. Only the audio level is far too low. It should be increased by at least a factor of 3! Please try that in Movavi. The Latex text is very good to have. But when I go in full screen mode, it is not sharp enough. I will send you an example of what I mean, what can be done to improve this situation. And in one instance on the screen was given in latex a translator T(a), but in words you said T(c). Please check that as well.

With kind regards,

Eckhard Hitzer

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]]>I really appreciate your comments and thoughts. Thank you! I edited the video and corrected the mistake.

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]]>Excellent! The spoken comment is quite helpful. And you did well in deciding to not read out every formula in detail. At the end, your name as the video producer and acknowledgement of the DAAD-RISE support should also appear briefly.

The video is already 3 minutes. So I do not really want to add to it. But it may be good at the beginning to only show the triplet of vectors a,b,c (blending out the rest) and rotate briefly, so that the viewer gets familiar with the vector arrangement by color.

The last generator is written on the screen as (ab)b(ab)T()T(). But please note that

(ab)b(ab) =*= a(ab) =*= b. I think the mistake is, that there is a missing inverse needed for the first bracket:

(ab)^{-1}b(ab). But that is just a small thing to fix I hope.

With kind regards,

Eckhard Hitzer

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]]>The reflections of the orthorhombic space group No. 47 look very convincing. I suggest that you should also try to experiment with central illumination/ambient lighting and with shrinking the plane size somewhat, which especially at the beginning, when you explain the reflections at the side faces of the cell will permit the viewer to get a better view of what is going on inside.

Especially when you show the rotation axis going through the cell origin at a vertex, it would be good to explain with vocal comment that the two reflections, e.g., at planes orthogonal to b and c give the rotation by two times 90 degrees = 180 degrees around the line of intersection of the two planes as axis in the direction of a. Etcetera. And perhaps a brief orthographic projection view of the first rotation in the direction of the axis would show the 180 degree angle very clearly.

Because here all three vectors are orthogonal, it would be the ideal point with vocal comment to point out at the beginning that the reflection at three orthogonal planes (each orthogonal to a, b, c respectively) reverses the orientation of every vector relative to the center of inversion.

In general it is good to recommend the viewers (perhaps in the blog text on top of the videos) to go into full screen mode, to use High Definition (because it is available and makes it easier to read the geometric algebra symmetry element expressions in the lower right corner).

On the About/Welcome page it would be good to explain what the view can see in the videos on the top right, i.e. the Space Group Number of the International Tables of Crystallography, the International Hermann Maugin Space Group Symbol, and the Geometric Algebra Space Group Symbol according to Coxeter, Hestenes and Holt. And in brackets the point group symbols in the two notation systems, as well as the name of the crystal class.

With kind regards, Eckhard Hitzer

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]]>The reflections and rotations can be seen very clearly. But I would suggest to add vocal comment [!] alongside the stream of images, explaining e.g. that a combination of elementary hyperplane reflection and orthogonal (to the hyperplane) translation leads to the extra plane of reflection located at half the distance of the translation. And similarly I would add such comments to the axis of rotation by 180 degrees and their combinations with orthogonal (to the axis, or in the plane of rotation) translations, which leads to a shift of the axis of rotation by half the distance of the translation applied. Similarly each center of inversion combined with a translation should be commented vocally as well.

In order to increase the visual 3D perception, at the beginning of each video I suggest that the whole cell or arrangement of cells with the graphical depictions of the symmetry elements to be explained should be globally rotated 2 or 3 times (using the function animate scene rotation).

For the orientation of the vectors a, b, c I suggest that two possibilities:

1) a points out of the screen, b points to the right, c points upward

or

2) a points to the right, b points into the screen, c points upward

With kind regards, Eckhard Hitzer

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]]>I think this is a great movie. Yesterday I watched it on a small (A5 size?) energy saving lap top computer. And there unfortunately the lower right corner information is hard to read, because it comes out very small and somewhat dim. I wonder if there would be a way to display that with bigger font size?

With kind regards, Eckhard Hitzer

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]]>Thank you for creating this very nice blog page. I think it would be good in the About/Welcome page to acknowledge the DAAD RISE internship program for its financial support and International Christian University for hosting you during this time.

With kind regards, Eckhard Hitzer

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