Talk:Descriptive geometry

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May I please offer suggestions for the first paragraph under Protocols? This is meant to be constructive rather than just critical.

The second sentence is confusing. The concept of projecting three dimensions onto two is already available from the first sentence of the introduction. The mention of scale is confusing. Unless multiple scales are specified, the reader should assume that a single consistent scale applies for the whole construction. What is meant by "an invisible (point view) axis receding ..."? This suggests perspective although that probably was not intended. What is meant by "... shares a full-scale view ..."? Each projection can be made independent of the others.

Rewriting the paragraph should be considered.

Regards, ...PeterEasthope (talk) 15:16, 18 November 2007 (UTC)Reply

I agree. I added one of those templates used for that purposes. There actually a lot more things needing work than this sentence, I'm confused also by the diagrams at the end, and most of the info is given without telling the sources. --Allefant (talk) 16:12, 18 November 2007 (UTC)Reply

Since the ancient Egyptian civilization, has been shown, through the discovery of drawings that they used orthogonal projections to build tombs with elliptical roof. Between the first century BC In the first century dp Vitruvius, in his pubblication entitled "De architectura" elements used as a representation of buildings and plants prospectuses he called iconography and orthographies. In later times, the work of Jacopo Barozzi da Vignola "the five orders of architecture" which used the method of Monge. During the same period, Alberto Dürer (1471-1528) called some graphs proceedings concerning conical, as flat sections of quadric cone and also the study of perspective. In 1600 Girard Desargues scholars and Guarino Guarini have laid the foundations for the emergence of discipline "descriptive geometry" of this name has been christened by the French scientist Gaspard Monge (1746-1818). In 1700 the book was published "descriptive geometry" which posed the fundamental rules of descriptive geometry. Rules that are aimed, above all, to be on an equal footing (that plan projection), the objects in 3D. Currently includes descriptive geometry as an integral part projective geometry where the most significant studies and should be conclusive to Jean Victor Poncelet (1788-1867) disciple of Monge. With the projective geometry is introduced the concept of geometric improper Authority (point, and right plan), which determines a substantial difference with Euclidean geometry, although the remaining valid postulates of Euclid. —Preceding unsigned comment added by 82.59.173.91 (talk) 14:18, 14 January 2008 (UTC)Reply

Placed below the current first image,  this image could illustrate this fact:  a plane of orthogonal projection is often chosen in order not to alter certain distances.  For example,  there is no vertex on the arc that represents partly the sphere on the top view,  yet it passes through all vertices in 3 D.  But it passes through certain images of vertices on an elevation or the other.  Every length inscribed near a double arrow is a true length…
  Arthur Baelde (talk) 13:18, 18 January 2024 (UTC)Reply

Characteristic horizontal and vertical lines of descriptive geometry are lacking on the current page.  Such thin lines connect each two images of a same point in two different projections.  On my second proposition of illustration,  only two equalities,  and more colours,  in manner that all correspondences between pentagonal faces are very visible.

More technical,  my first proposition brings to the fore certain true lengths and true angle measures,  in well chosen projections.  On every other pair of views of my second proposition,  a rule of  descriptive geometry is deliberately disregarded not to muddle the drawings:  no dashed lines for hidden segments.  What example of descriptive geometry do you prefer?
  Arthur Baelde (talk) 13:35, 27 March 2024 (UTC)Reply

We should use images that are typical for descriptive geometry. Images of polyhedra are not. It would make sense to show images of a house with a slanted roof, where one projection shows the correct measurements of a wall, and another one those of a plane of the roof. --Watchduck (quack) 17:55, 27 March 2024 (UTC)Reply

Yes,  technical usings are possible.  Here is an interesting example,
but without verticals and horizontals between the projections.
  Arthur Baelde (talk) 16:07, 28 March 2024 (UTC)Reply

Descriptive geometry is primally in pure geometry,  and a polyhedron is greatly easier to conceive than the classical and almost obsessional example in so‑called descriptive geometry:  a planar cross section of cone,  often drawn in incomprehensible manner.  Therefore,  contrary to my first idea in this section,  I propose as very first image of the article one of the two I show here,  of which I am the author.  Further on another image in applied mathematics could be inserted,  like the current first image.  Here are my first proposition and my second one to illustrate the article in SVG,  which one do you prefer?
  Arthur Baelde (talk) 13:35, 30 March 2024 (UTC)Reply

I don't think that pure geometry makes good examples. I have created drawings of a simple house.

The dormer is a cone, and creates two conic sections: An ellipse with the window, and a hyperbola with the roof.

shed with conic dormer

--Watchduck (quack) 00:55, 6 April 2024 (UTC)Reply

Caption of my second proposition slightly improved.
  Arthur Baelde (talk) 13:06, 6 April 2024 (UTC)Reply

This image is not a helpful lead image at all - it serves to confuse rather than to illustrate. - MrOllie (talk) 13:50, 4 September 2024 (UTC)Reply

There should be more references to texts on the procedures. For instance, https://archive.org/details/descriptivegeome033051mbp has some excellent diagrams and descriptions in the first 30 of its 300 pages. It might be good to refer to a text for some of these techniques -- Drf5n (talk) 06:10, 9 May 2025 (UTC)Reply