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surfacenets.c
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surfacenets.c
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// SurfaceNets, 10 August 2015, Roberto Toro
// translated from Mikola Lysenko
// http://0fps.net/2012/07/12/smooth-voxel-terrain-part-2/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
typedef struct {
float x,y,z;
} float3D;
typedef struct {
int a,b,c;
} int3D;
typedef struct {
int np,nt;
float3D *p;
int3D *t;
} Mesh;
int cube_edges[24];
int edge_table[256];
int buffer[4096];
void init_surfacenets(void)
{
int i,j,p,em,k = 0;
for(i=0; i<8; ++i) {
for(j=1; j<=4; j=j<<1) {
p = i^j;
if(i <= p) {
cube_edges[k++] = i;
cube_edges[k++] = p;
}
}
}
for(i=0; i<256; ++i) {
em = 0;
for(j=0; j<24; j+=2) {
int a = !(i & (1<<cube_edges[j])); // was !!, which in js turns into boolean false null, undefined, etc
int b = !(i & (1<<cube_edges[j+1]));
em |= a != b ? (1 << (j >> 1)) : 0; // was !==
}
edge_table[i] = em;
}
}
void SurfaceNets(float *data, int *dims, float level, Mesh *mesh, int storeFlag)
{
float3D *vertices=mesh->p;
int3D *faces=mesh->t;
int n = 0;
float x[3];
int R[3];
float *grid = (float*)calloc(8,sizeof(float));
int buf_no = 1;
int *buffer;
int buffer_length=0;
int vertices_length=0;
int faces_length=0;
int i,j,k;
R[0]=1;
R[1]=dims[0]+1;
R[2]=(dims[0]+1)*(dims[1]+1);
if(R[2] * 2 > buffer_length)
buffer = (int*)calloc(R[2] * 2,sizeof(int));
for(x[2]=0; x[2]<dims[2]-1; ++x[2])
{
int m = 1 + (dims[0]+1) * (1 + buf_no * (dims[1]+1));
for(x[1]=0; x[1]<dims[1]-1; ++x[1], ++n, m+=2)
for(x[0]=0; x[0]<dims[0]-1; ++x[0], ++n, ++m)
{
int mask = 0, g = 0, idx = n;
for(k=0; k<2; ++k, idx += dims[0]*(dims[1]-2))
for(j=0; j<2; ++j, idx += dims[0]-2)
for(i=0; i<2; ++i, ++g, ++idx)
{
float p = data[idx]-level;
grid[g] = p;
mask |= (p < 0) ? (1<<g) : 0;
}
if(mask == 0 || mask == 0xff)
continue;
int edge_mask = edge_table[mask];
float3D v = {0.0,0.0,0.0};
int e_count = 0;
for(i=0; i<12; ++i)
{
if(!(edge_mask & (1<<i)))
continue;
++e_count;
int e0 = cube_edges[ i<<1 ]; //Unpack vertices
int e1 = cube_edges[(i<<1)+1];
float g0 = grid[e0]; //Unpack grid values
float g1 = grid[e1];
float t = g0 - g1; //Compute point of intersection
if(fabs(t) > 1e-6)
t = g0 / t;
else
continue;
k=1;
for(j=0; j<3; ++j)
{
int a = e0 & k;
int b = e1 & k;
if(a != b)
((float*)&v)[j] += a ? 1.0 - t : t;
else
((float*)&v)[j] += a ? 1.0 : 0;
k=k<<1;
}
}
float s = 1.0 / e_count;
for(i=0; i<3; ++i)
((float*)&v)[i] = x[i] + s * ((float*)&v)[i];
buffer[m] = vertices_length;
if(storeFlag)
vertices[vertices_length++]=v;
else
vertices_length++;
for(i=0; i<3; ++i)
{
if(!(edge_mask & (1<<i)) )
continue;
int iu = (i+1)%3;
int iv = (i+2)%3;
if(x[iu] == 0 || x[iv] == 0)
continue;
int du = R[iu];
int dv = R[iv];
if(storeFlag)
{
if(mask & 1)
{
faces[faces_length++]=(int3D){buffer[m], buffer[m-du-dv], buffer[m-du]};
faces[faces_length++]=(int3D){buffer[m], buffer[m-dv], buffer[m-du-dv]};
}
else
{
faces[faces_length++]=(int3D){buffer[m], buffer[m-du-dv], buffer[m-dv]};
faces[faces_length++]=(int3D){buffer[m], buffer[m-du], buffer[m-du-dv]};
}
}
else
faces_length+=2;
}
}
n+=dims[0];
buf_no ^= 1;
R[2]=-R[2];
}
mesh->np=vertices_length;
mesh->nt=faces_length;
}
int main(int argc, char *argv[])
{
// FILE *f;
float *vol;
int dim[3];
int i,j,k;
Mesh m;
dim[0]=100;
dim[1]=100;
dim[2]=100;
vol=(float*)calloc(dim[0]*dim[1]*dim[2],sizeof(float));
for(i=0;i<dim[0];i++)
for(j=0;j<dim[1];j++)
for(k=0;k<dim[2];k++)
if(pow(i-dim[0]/2,2)+pow(j-dim[1]/2,2)+pow(k-dim[2]/2,2)<10*10)
vol[k*dim[1]*dim[0]+j*dim[0]+i]=100;
init_surfacenets();
SurfaceNets(vol,dim,50.0,&m,0); // 1st pass: evaluate memory requirements
m.p=(float3D*)calloc(m.np,sizeof(float3D));
m.t=(int3D*)calloc(m.nt,sizeof(int3D));
SurfaceNets(vol,dim,50.0,&m,1); // 2nd pass: store vertices and triangles
printf("%i %i\n",m.np,m.nt);
for(i=0;i<m.np;i++)
printf("%f %f %f\n",m.p[i].x,m.p[i].y,m.p[i].z);
for(i=0;i<m.nt;i++)
printf("%i %i %i\n",m.t[i].a,m.t[i].b,m.t[i].c);
return 0;
}