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The following patch fixes some bugs reported at
http://www.povray.org/download/3.5-bugs.php.
In particular it should fix:
http://news.povray.org/3b99052c@news.povray.org (at least the 2nd)
http://news.povray.org/Xns9115B92CF7D8ACQ@204.213.191.226
http://news.povray.org/Xns91203DC7F3CCQ@204.213.191.226
http://news.povray.org/3be5f0b2@news.povray.org
A simple explanation (without formulas) is:
All bug reports concern with big/small blob objects.
Let's represent an object using millimeters as pov unit, we'll
have a direction of 1 mm, and the depth of the intersections will be
in mm. But if you represent the same object in meters, the ray direction
is 1 m long, and the depth of the intersections are now in m. The problem
is that the equations representing these intersections are fourth order
polinomials and it is easy to exceed limits and lose accuracy.
So, when computing the equations I scale ray's direction proportionally
to a dimension of the object, and then the computed depths
are scaled back to the original unit.
The patch is against blob.cpp (as it is in povray-3.50a for linux).
If it is not worth to be included in the vanilla-povray (it needs
extensive tests), I hope it's a good starting point for those interested
in fix these bugs.
Comments are welcome.
HTH Massimo
--- src/blob.cpp.ex Sat Nov 2 09:30:34 2002
+++ src/blob.cpp Sat Nov 2 09:30:34 2002
@@ -344,8 +344,11 @@
start_dist = 0.0;
}
+ DBL Max_Bound = intervals[0].bound;
for (i = 0; i < cnt; i++)
{
+ if (intervals[i].bound > Max_Bound)
+ Max_Bound = intervals[i].bound;
intervals[i].bound -= start_dist;
}
@@ -353,6 +356,20 @@
VAddScaledEq(P, start_dist, D);
+ if (Max_Bound != 0)
+ {
+ VScaleEq(D, Max_Bound);
+
+ for (i = 0; i < cnt; i++)
+ {
+ intervals[i].bound /= Max_Bound;
+ }
+ }
+ else
+ {
+ Max_Bound = 1;
+ }
+
/* Clear out the coefficients. */
coeffs[0] =
@@ -389,6 +406,7 @@
VDot(t0, V1, V1);
VDot(t1, V1, D);
+ t2 = Max_Bound * Max_Bound;
c0 = Element->c[0];
c1 = Element->c[1];
@@ -396,9 +414,9 @@
fcoeffs = &(Element->f[0]);
- fcoeffs[0] = c0;
- fcoeffs[1] = 4.0 * c0 * t1;
- fcoeffs[2] = 2.0 * c0 * (2.0 * t1 * t1 + t0) + c1;
+ fcoeffs[0] = c0 * t2 * t2;
+ fcoeffs[1] = 4.0 * c0 * t1 * t2;
+ fcoeffs[2] = 2.0 * c0 * (2.0 * t1 * t1 + t0 * t2) + c1 * t2;
fcoeffs[3] = 2.0 * t1 * (2.0 * c0 * t0 + c1);
fcoeffs[4] = t0 * (c0 * t0 + c1) + c2;
@@ -584,7 +602,7 @@
{
/* Correct distance. */
- dist = (dist + start_dist) / len;
+ dist = (dist * Max_Bound + start_dist) / len;
if ((dist > DEPTH_TOLERANCE) && (dist < Max_Distance))
{
Post a reply to this message
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Massimo Valentini wrote:
>
> [...]
>
> The patch is against blob.cpp (as it is in povray-3.50a for linux).
> If it is not worth to be included in the vanilla-povray (it needs
> extensive tests), I hope it's a good starting point for those interested
> in fix these bugs.
>
> Comments are welcome.
>
> [...]
I think in general it would be better to post modified versions of the
original files with marked changes than a diff. It's always possible that
people who want to use your modifications don't have exactly the same file
as you and have problems applying the changes.
Christoph
--
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 28 Oct. 2002 _____./\/^>_*_<^\/\.______
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"Christoph Hormann" ha scritto
:
:
: I think in general it would be better to post modified versions of the
: original files with marked changes than a diff. It's always possible that
: people who want to use your modifications don't have exactly the same file
: as you and have problems applying the changes.
:
Well, I dont want anybody to apply the diff against a custom blob.cpp
I thought that it is possible to extract from the source tar(zip), a copy
of the original blob.cpp and apply the patch against it. This way the diff
already marks clearly the changes, IMHO better than in a 70Kb cpp file.
Anyway I posted the whole file to povray.binaries.programming.
Massimo
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