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# View of /branches/charisee/test/lic2.diderot

Mon Jun 3 19:41:56 2013 UTC (6 years, 3 months ago) by jhr
File size: 1387 byte(s)
```  Create new branch for Charisee's Einstein stuff
```
```// lic.diderot
//
// simple demo of the line integral convolution (LIC) method
// of vector field viz
//
// process output with:
// unu reshape -i mip.txt -s 300 200 | unu quantize -b 8  -o lic.png

int imgSizeX = 300;
int imgSizeY = 200;
real h = 0.01;    // step size of integration
int stepNum = 25; // take this many steps both upstream and downstream

field#1(2)[2] V = load("../data/vorttest.nrrd") ⊛ ctmr;
field#0(2)[] R = load("../data/vorttest-rand.nrrd") ⊛ tent;

strand LIC (int xi, int yi) {
real xx = lerp(0.0, 3.0, -0.5, real(xi), real(imgSizeX)-0.5);
real yy = lerp(0.0, 2.0, -0.5, real(yi), real(imgSizeY)-0.5);
vec2 pos0 = [xx,yy];
vec2 pos = [xx,yy];
bool forw = true;
output real sum = R(pos0);
int step = 0;

update {
if (forw) {
pos += h*V(pos + 0.5*h*V(pos));
sum += R(pos);
if (step == stepNum) {
forw = false;
pos = pos0;
}
} else {  // going backwards, not forward
pos -= h*V(pos - 0.5*h*V(pos));
sum += R(pos);
if (step == stepNum) {
// modulate output by velocity at initial position
sum = |V(pos0)|*sum/real(1 + 2*stepNum);
stabilize;
}
}
}
}

initially [ LIC(xi, yi) | yi in 0..(imgSizeY-1), xi in 0..(imgSizeX-1) ];
```