1) For the representation of three components, triangle diagrams (equilateral triangle) are used, for example in geology and chemistry. I found that there are two different types of such triangular diagrams: Sometimes the coordinates are parallels to the sides, and another time perpendicular to the sides. I couldn't found references in the literature. Is my assumption correct?
2) For the presentation of four components, tetrahedral diagrams (regular tetrahedron) is used, for example in geology and chemistry. a) What are the formulas for converting from Cartesian coordinates to tetrahedral coordinates? b) Is there also the possibility to draw the coordinates along the side parallels (face parallels) of the tetrahedron? c) Are there similar to the tetrahedral diagram higher-dimensional diagrams in three dimensions, perhaps the other Platonic solids?