# I need help with that "fake" perspective transformation jazz

**URL:** <https://forum.kirupa.com/t/i-need-help-with-that-fake-perspective-transformation-jazz/327805>\
**Category:** Uncategorized\
**Created:** [March 29, 2012, 6:43pm UTC](https://forum.kirupa.com/t/i-need-help-with-that-fake-perspective-transformation-jazz/327805 "2012-03-29T18:43:42Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![GabeLaneG](https://avatars.discourse-cdn.com/v4/letter/g/9de053/32.png) [@GabeLaneG](https://forum.kirupa.com/u/GabeLaneG)\
**Post date:** [March 29, 2012, 6:43pm UTC](https://forum.kirupa.com/t/i-need-help-with-that-fake-perspective-transformation-jazz/327805/1 "2012-03-29T18:43:42Z")

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Basically that method of fitting a bitmap texture onto a parallelogram, by splitting the parallelogram into two triangles and skew/shearing the two separate copies of the texture to be lined up with it’s respective triangle.

Senocular wrote a [pretty good tutorial](http://www.senocular.com/flash/tutorials/texturemapping/) on it, but I’m stuck on some little details and or conceptual stuff, I’m not sure. :puzzle: Yeah, I’m actually pretty confused. lol

First question, in the transform matrix, the b and c multipliers (skew and shear), what does it mean exactly? I played around with it and found that shearing by a factor of one, the angle formed by the slope (the slope of the two top or bottom ‘points’) of the shape was 45˚. So, 1 = 45; 0.5 = 22.5, etc. Am I on the right track or was the 45 angle observation just a coincidence? If so, how exactly do I find the skew factor?

I’ll probably have more questions later on, but I can’t think of them at the moment …