houdini heighfield

教程：https://youtu.be/tJu9Yj8uv7Q     https://youtu.be/ez1cWETOaXk

如有冒犯，敬请告之，侵删

string costattrib = chs('costattrib');
string directionattrib = chs('directionattrib'); //
int usecost = chi('usecost');
float stepsize = ch('stepsize');
float stepsizemultiplier = ch('stepsizeMultiplier');
float mindist = ch('mindist');
float maxdist = ch('maxdist');

float dist = stepsize;
float tolerance = 0.0001;

vector pos[]={};
float dists[] = {};

int hitpr=-1;
vector hituv = 0;

vector p = @P;
xyzdist(1,p,hitpr,hituv);
p = primuv(1,'P',hitpr,hituv);
vector grad = primuv(1,'grad',hitpr,hituv); //
//grad = cross(grad,{0,1,0});
//vector grad = -volumegradient(1,hitpr,p);
//float cost = volumesample(1,hitpr,p);
float cost = primuv(1,'cost',hitpr,hituv);
float lastcost = cost;

append(pos,p);
append(dists,0);

float sumdist = 0;
while(sumdist <= maxdist)
{
        p+= normalize(grad)*stepsize;
        xyzdist(1,p,hitpr,hituv);
        p=primuv(1,'P',hitpr,hituv);
        //grad = -volumegradient(1,hitpr,p);
        //cost = volumesample(1,hitpr,p);
        grad = primuv(1,'grad',hitpr,hituv);
        //grad = cross(grad,{0,1,0})
        
        cost = primuv(1,costattrib,hitpr,hituv);
        
        if(usecost && cost >= lastcost-tolerance) //
        {
            stepsize  *= stepsizemultiplier;
            if(abs(stepsize) < tolerance)
                break;
        }
        else
        {
             dist = distance(pos[-1],p);
             if(dist < tolerance)
                 break;

            sumdist +=dist;
            append(pos,p);
            append(dists,sumdist);
            
            lastcost = cost;
            
        }
}

if(sumdist >= mindist)
{
        float m = 1.0/sumdist;
        int count = len(pos);
        int pts[]={};
        for(int i=0;i<count;++i)
        {
                int pt = addpoint(0,pos[i]);
                float s = dists[i]*m;
                vector color = chramp('color',s);
                setpointattrib(0,'Cd',pt,color);
                append(pts,pt);
        }
        addprim(0,'polyline',pts);
}

removepoint(0,@ptnum);