Just My Life & My Work

透視縮短 (Foreshortening)

電腦視覺在介紹輻射線測定(Radiometry)時介紹透視縮短(Foreshortening),剛開始很疑惑這個字的意思,後來想一想之後,其實就跟我對透視投影的瞭解一樣,物體距離眼睛越遠,則影像越小

先看WiKi怎麼說:Foreshortening

Perspective Foreshortening

A: No perspective foreshortening, and B: Perspective foreshortening.

Foreshortening refers to the visual effect or optical illusion that an object or distance appears shorter than it actually is because it is angled toward the viewer.

Although foreshortening is an important element in art where visual perspective is being depicted, foreshortening occurs in other types of two-dimensional representations of three-dimensional scenes. Some other types where foreshortening can occur include oblique parallel projection drawings.

Figure shows two different projections of a stack of two cubes, illustrating oblique parallel projection foreshortening (“A") and perspective foreshortening (“B").

直接來看一個例子,就會更好瞭解什麼是透視縮短(Foreshortening),簡單來說~遠者小,近者大

foreshortened

這位女角色的右手跟左手不一樣大小,這就是所謂的透視縮短(foreshortening)。

Comments on: "透視縮短 (Foreshortening)" (3)

  1. 不是這樣的,按照Wiki的解釋,是指物體的長度會因為向著觀看者而感覺變短,與近者大遠者小此一現象無關,例如Wiki中提到的"The Lamentation over the Dead Christ"這幅畫即是藝術史中Forshortennig的範例,圖中耶穌的遺體向著觀畫者,因此身體變得短,腿也很短,但是並沒有出現近者大遠者小的現象。

    總之,透視投影會出現近者大遠者小的現象,平行投影則不會,而Forshortening這現象則無論透視投影與平行投影皆有之。

  2. […] 透視變換相當值得探討,之前稍微研究了透視投影和透視縮短,還在計算機圖學課上寫了透視投影的結果,如今會了OpenCV函式庫,直接呼叫來玩玩更加有趣~ […]

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