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[diderot] View of /branches/charisee/ertest/test2/cniso3d/cniso3d.diderot
 [diderot] / branches / charisee / ertest / test2 / cniso3d / cniso3d.diderot

# View of /branches/charisee/ertest/test2/cniso3d/cniso3d.diderot

Fri Mar 6 16:37:08 2015 UTC (4 years, 6 months ago) by cchiw
File size: 1407 byte(s)
`|matrix field| and speed up`
```/*

../../../bin/diderotc cniso3d.diderot \
&& ./cniso3d \
&& unu crop -i cniso3d.txt -min 0 0 -max 1 M | \
unu jhisto -b 600 600 -min -1.2 -1.2 -max 1.2 1.2 -t float | \
unu 1op log1p | \
unu quantize -b 8 -o cniso3d.png \
&& open cniso3d.png

*/

//field#3(3)[3] G = ∇V;
field#2(3)[3] G = ∇V;
field#2(3)[3,3] H = ∇⊗∇V;
field#2(3)[] F = G•H•G/|G|;

int grid = 30;
int stepsMax = 10;
real epsilon = 0.0001;

strand RootFind(real xi,real xj, real xk) {
output vec3 x = [xi,xj,xk];
int steps = 0;
update {
// Stop if we're no longer inside or taken too many steps.
if (!inside(x, V) || steps > stepsMax)
die;
// subsequent expressions are undefined if |∇F| is zero
if (|∇F(x)| == 0.0)
die;
// ALSO, for canny, bail if gradient magnitude is too low
if (|∇V(x)| < 5)
die;
// the Newton-Raphson step
vec3 delta = normalize(∇F(x)) * F(x)/|∇F(x)|;
// we've converged if the change is small enough
if (|delta| < epsilon)
stabilize;
x -= delta;
steps += 1;
}
}

initially { RootFind(lerp(-2, 2, -0.5, ui, grid-0.5),
lerp(-2, 2, -0.5, vi, grid-0.5),
lerp(-2, 2, -0.5, wi, grid-0.5))
| wi in 0..(grid-1), vi in 0..(grid-1), ui in 0..(grid-1) };
```