Nieminen Juha wrote:
> 
> Jerome M. BERGER <jbe### [at] enstfr> wrote:
> : But when you scale a normal
> : by 5, the way pov does it is equivalent to scaling by <5, 1, 5>
> 
>   Wrong. The slope doesn't change. Thus, the apparent depth is scaled by 5,
> not by 1.
	No, the slope *does* change... Try it.

>   To really scale the apparent depth by 1 instead of 5, the slopes would
> have to be scaled by 1/5. Povray does not do this. This is easy to test:
> Make an object with a normal modifier. Scale that object 100 times larger
> and move the camera and the light source 100 times farther away. If what
> you say was true, now the slopes would be 1/100 of the original and the
> apparent depth would have not changed, so the normal modifier should be
> almost invisible. This, of course, is not so. The slopes are not changed
> and the apparent depth gets scaled by 100 too.
	I did precisely this test and if the normal is inside a normal_map I
get what you said, but if the normal is on its own it *is* almost
invisible...

>   Now make this same test in megapov. What happens is that megapov will
> scale the _slopes_ by 100 as well, which means that the apparent depth
> of the surface would be 10000 after scaling.
	I just did the test with megapov 0.2 and the scene was the same no
matter what scale factor I used...

		Jerome
-- 
*******************************

* they'll tell you what can't * mailto:ber### [at] inamecom
* be done and why...          * http://www.enst.fr/~jberger
* Then do it.                 *
*******************************

Post a reply to this message