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[diderot] View of /examples/iso2d-demo/iso2d.diderot
 [diderot] / examples / iso2d-demo / iso2d.diderot

# View of /examples/iso2d-demo/iso2d.diderot

Fri Jun 8 13:22:03 2012 UTC (7 years ago) by jhr
File size: 1542 byte(s)
```  Tweaking iso2d demo
```
```// iso2d
//
// Demo of finding isocontours via Newton-Raphson method.
// Initializes positions on a grid, and each update applies one
// step of Newton-Raphson.
//
// Process output with:
// unu jhisto -i iso2d.txt -b 512 512 -min 0 0 -max 1 1 | unu 2op neq - 0 | unu quantize -b 8  -o iso2d.png

int gridSize = 300;
field#1(2)[] F = ctmr ⊛ diderot;
input int stepsMax = 12;
real epsilon = 0.0001;

strand sample (int ui, int vi) {
// world is 1x1 centered at (0.5, 0.5)
output vec2 pos = [lerp(0.0, 1.0, -0.5, real(ui), real(gridSize)-0.5),
lerp(0.0, 1.0, -0.5, real(vi), real(gridSize)-0.5)];
// set the isvalue to 50, 30, or 10, depending on whichever we're closest to
real isoval = 50.0 if F(pos) >= 40.0
else 30.0 if F(pos) >= 20.0
else 10.0;
int steps = 0;
update {
// We bail if we're no longer inside or taken too many steps.
if (!inside(pos, F) || steps > stepsMax) {
die;
}
if (|grad| == 0.0) {    // can't compute step if |∇F|, so have to bail
die;
}