HermanS nous apporta ses lumieres ainsi en ce 2004-09-29 15:18... :

>I want to illustrate some elements about perspective. So I made a model 
>of a room and also of a tower. I don't have any problems to reproduce 
>one point and two point perspective. 
>Now I want to illustrate three point perspective using the tower and 
>reproducing the effect of rotating a photographic camera slightly as to 
>get the image of the whole tower on the picture. 
>I found the possibility to rotate the camera (ex. around the X-axis), 
>but the result isn't what I think it should be. What about the 
>combination of rotating the camera and the "look_at" and "direction" 
>directives? Does it have any sense to rotate a camera and to maintain 
>this two elements?
>  
>
Unless the camera is at <0,0,0> any rotation will also move it. If the 
camera is at <0,0,-10> and you rotate it by -30*x, it's now at 
<0,-5,-8.66> and possibly under your ground. Personaly, I only rotate my 
camera if I want to tilt it lateraly or turn it in an animation.
Using look_at is a good way to orient your camera. You place it where 
you want and set the center point of it's field of vision. The direction 
is also good but may be less intuitive to some, me included.

Alain

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