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major update for tin.h

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张壹
2021-09-16 17:09:53 +08:00
parent 760db80652
commit f5e1e808e1
4 changed files with 2541 additions and 72 deletions
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218
tin.h
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@@ -1,10 +1,10 @@
/**
* @defgroup TIN
*
* @brief Generation of a Triangular Irregular Network (TIN) from a dense DEM grid
* @brief Generation of a Triangular Irregular Network (TIN) from a dense DEM grid.
*
* @author Yi Zhang
* @date 2021-09-15
* @date 2021-09-16
*/
#ifndef _TIN_DELAUNAY_H
@@ -108,7 +108,7 @@ struct triangle
l2x = inx - vert[i]->x;
l2y = iny - vert[i]->y;
if ((l1x*l2y - l1y*l2x) < 0)
if ((l1x*l2y - l1y*l2x) < 0) // This condition includes points on the triangle's edge
{
return false;
}
@@ -126,25 +126,47 @@ struct triangle
};
// End triangle definition
// Start DEM definition
struct dem_point
{
double x, y; // position of the DEM location
double elev; // elevation at the DEM location
triangle *host; // host triangle of the DEM location
std::vector<triangle*> circum_host; // triangles which circumcircles include the location
dem_point() : x(NAN), y(NAN), elev(NAN), host(nullptr) {}
dem_point(double inx, double iny, double inelev) {set(inx, iny, inelev);}
void set(double inx, double iny, double inelev)
{
x = inx; y = iny; elev = inelev; host = nullptr;
circum_host.clear();
return;
}
};
// End DEM definition
/**
* @brief Generate the TIN from the DEM grid
*
* @param[in] dem Input DEM grid (Ordered from lower left corner to the upper right corner)
* @param[in] xmin The minimal coordinate of the DEM grid on the x-axis
* @param[in] xmax The maximal coordinate of the DEM grid on the x-axis
* @param[in] ymin The minimal coordinate of the DEM grid on the y-axis
* @param[in] ymax The maximal coordinate of the DEM grid on the y-axis
* @param[in] dx Data spacing of the DEM grid on the x-axis
* @param[in] dy Data spacing of the DEM grid on the y-axis
* @param out_verts The output vector of vertex's pointers. The user need to destroy the memories allocated by the function before destroy the vector
* @param out_tris The output vector of triangle's pointers. The user need to destroy the memories allocated by the function before destroy the vector
* @param[in] maxi_err Threshold to quit the algorithm. The default is 1e-2
* @param[in] dem Input DEM grid (Ordered from lower left corner to the upper right corner)
* @param[in] xmin The minimal coordinate of the DEM grid on the x-axis
* @param[in] xmax The maximal coordinate of the DEM grid on the x-axis
* @param[in] ymin The minimal coordinate of the DEM grid on the y-axis
* @param[in] ymax The maximal coordinate of the DEM grid on the y-axis
* @param[in] dx Data spacing of the DEM grid on the x-axis
* @param[in] dy Data spacing of the DEM grid on the y-axis
* @param out_verts The output vector of vertex's pointers. The user need to destroy the memories allocated by the function before destroy the vector
* @param out_tris The output vector of triangle's pointers. The user need to destroy the memories allocated by the function before destroy the vector
* @param[in] maxi_err Threshold to quit the algorithm. The default is 1e-0
* @param[in] err_records If this pointer is not NULL, record maximal error values after each insertion of vertex.
*/
void dem2tin(const std::vector<double> &dem, double xmin, double xmax, double ymin, double ymax,
double dx, double dy, std::vector<vertex2dc*> &out_verts, std::vector<triangle*> &out_tris, double maxi_err = 1e-2)
double dx, double dy, std::vector<vertex2dc*> &out_verts, std::vector<triangle*> &out_tris,
double maxi_err = 1e-0, std::vector<double> *err_records = nullptr)
{
if (!out_verts.empty()) out_verts.clear();
if (!out_tris.empty()) out_tris.clear();
if (err_records != nullptr && !err_records->empty()) err_records->clear();
if (dx <= 0.0 || dy <= 0.0 || maxi_err <= 0.0) return;
if (xmin >= xmax || ymin >= ymax || (xmin + dx) > xmax || (ymin + dy) > ymax) return;
@@ -154,22 +176,37 @@ void dem2tin(const std::vector<double> &dem, double xmin, double xmax, double ym
if (dem.size() != xnum*ynum) return;
// Prepare the DEM points
std::vector<dem_point> dem_grid(xnum*ynum);
std::vector<dem_point>::iterator d_iter;
for (int i = 0; i < ynum; ++i)
{
for (int j = 0; j < xnum; ++j)
{
dem_grid[j + i*xnum].set(xmin + dx*j, ymin + dy*i, dem[j + i*xnum]);
}
}
vertex2dc *tmp_vert = nullptr;
tmp_vert = new vertex2dc(xmin, ymin, dem[0], out_verts.size()); // lower left corner
tmp_vert = new vertex2dc(xmin, ymin, dem_grid[0].elev, out_verts.size()); // lower left corner
out_verts.push_back(tmp_vert);
d_iter = dem_grid.begin(); dem_grid.erase(d_iter);
tmp_vert = new vertex2dc(xmax, ymin, dem[xnum-1], out_verts.size()); // lower right corner
tmp_vert = new vertex2dc(xmax, ymin, dem_grid[xnum-2].elev, out_verts.size()); // lower right corner. Note the first location is already erased
out_verts.push_back(tmp_vert);
d_iter = dem_grid.begin() + (xnum - 2); dem_grid.erase(d_iter);
tmp_vert = new vertex2dc(xmax, ymax, dem[xnum*ynum-1], out_verts.size()); // upper right corner
tmp_vert = new vertex2dc(xmax, ymax, dem_grid[xnum*ynum-3].elev, out_verts.size()); // upper right corner. Note the first two locations are already erased
out_verts.push_back(tmp_vert);
d_iter = dem_grid.begin() + (xnum*ynum - 3); dem_grid.erase(d_iter);
tmp_vert = new vertex2dc(xmin, ymax, dem[xnum*(ynum-1)], out_verts.size()); // upper left corner
tmp_vert = new vertex2dc(xmin, ymax, dem_grid[xnum*(ynum-1) - 2].elev, out_verts.size()); // upper left corner. Note the first two locations are already erased
out_verts.push_back(tmp_vert);
d_iter = dem_grid.begin() + (xnum*(ynum-1) - 2); dem_grid.erase(d_iter);
triangle *tmp_tri = nullptr;
std::vector<triangle*> cnst_tri;
std::vector<triangle*> cnst_tri, new_tri;
std::vector<triangle*>::iterator t_iter;
if (!is_collinear(out_verts[0], out_verts[1], out_verts[2])) // Do not create triangle if the vertexes are collinear
@@ -184,12 +221,39 @@ void dem2tin(const std::vector<double> &dem, double xmin, double xmax, double ym
out_tris.push_back(tmp_tri);
}
// Find host triangle for all DEM locations
for (int i = 0; i < dem_grid.size(); ++i)
{
for (int t = 0; t < out_tris.size(); ++t)
{
if (out_tris[t]->bound_location(dem_grid[i].x, dem_grid[i].y))
{
dem_grid[i].host = out_tris[t];
break; // already found, no need to search more
}
}
}
// Find circum_host triangles for all DEM locations
double dist;
for (int i = 0; i < dem_grid.size(); ++i)
{
for (int t = 0; t < out_tris.size(); ++t)
{
dist = (out_tris[t]->cx - dem_grid[i].x) * (out_tris[t]->cx - dem_grid[i].x)
+ (out_tris[t]->cy - dem_grid[i].y) * (out_tris[t]->cy - dem_grid[i].y);
if ((dist - out_tris[t]->cr) <= ZERO) // Points on the circumcircle are also included
{
dem_grid[i].circum_host.push_back(out_tris[t]);
// no beak here. There might be more than one triangle's circumcircle includes the DEM location
}
}
}
int now_maxi_id;
double now_x, now_y, now_err;
double now_maxi_err;
double now_err, now_maxi_err;
bool removed;
double dist;
edge tmp_edge;
std::vector<edge> cnst_edge;
std::vector<edge>::iterator e_iter;
@@ -197,48 +261,52 @@ void dem2tin(const std::vector<double> &dem, double xmin, double xmax, double ym
do // quit til the threshold is meet
{
// loop all DEM data to find the location with maximal error
// this part is very time consuming. We will fix it later
now_maxi_err = -1.0;
for (int i = 0; i < xnum*ynum; ++i)
for (int i = 0; i < dem_grid.size(); ++i)
{
now_x = (i%xnum)*dx + xmin;
now_y = (i/xnum)*dy + ymin;
for (int e = 0; e < out_tris.size(); ++e)
now_err = fabs(dem_grid[i].host->interpolate(dem_grid[i].x, dem_grid[i].y) - dem_grid[i].elev);
if (now_err > now_maxi_err)
{
if (out_tris[e]->bound_location(now_x, now_y))
{
now_err = fabs(out_tris[e]->interpolate(now_x, now_y) - dem[i]);
if (now_err > now_maxi_err)
{
now_maxi_err = now_err;
now_maxi_id = i;
}
break;
}
now_maxi_err = now_err;
now_maxi_id = i;
}
}
if (err_records != nullptr)
{
err_records->push_back(now_maxi_err);
}
// create a new vertex
now_x = (now_maxi_id%xnum)*dx + xmin;
now_y = (now_maxi_id/xnum)*dy + ymin;
tmp_vert = new vertex2dc(now_x, now_y, dem[now_maxi_id], out_verts.size());
tmp_vert = new vertex2dc(dem_grid[now_maxi_id].x, dem_grid[now_maxi_id].y, dem_grid[now_maxi_id].elev, out_verts.size());
out_verts.push_back(tmp_vert);
// determine triangles that include the point and add the triangle to the cnst_tri and remove it from out_tris
// this is also a part that could take a lot of time if we are working with a large amount of points. We will fix it later
// Move triangles which circumcircles include the new vertex to the cnst_tri and remove it from out_tris
cnst_tri.clear();
for (t_iter = out_tris.begin(); t_iter != out_tris.end(); )
for (int i = 0; i < dem_grid[now_maxi_id].circum_host.size(); ++i)
{
tmp_tri = *t_iter;
dist = (tmp_tri->cx - now_x) * (tmp_tri->cx - now_x) + (tmp_tri->cy - now_y) * (tmp_tri->cy - now_y);
if ((dist - tmp_tri->cr) <= ZERO) // Points on the circumcircle are also included
{
t_iter = out_tris.erase(t_iter);
cnst_tri.push_back(tmp_tri);
}
else t_iter++;
cnst_tri.push_back(dem_grid[now_maxi_id].circum_host[i]);
}
for (int i = 0; i < cnst_tri.size(); ++i)
{
for (t_iter = out_tris.begin(); t_iter != out_tris.end(); )
{
tmp_tri = *t_iter;
if (cnst_tri[i] == tmp_tri)
{
t_iter = out_tris.erase(t_iter);
break; // no need to search more
}
else t_iter++;
}
}
// clear host and circumcircle triangles for the used DEM location
dem_grid[now_maxi_id].host = nullptr;
dem_grid[now_maxi_id].circum_host.clear();
d_iter = dem_grid.begin() + now_maxi_id; dem_grid.erase(d_iter);
// loop to remove duplicate edges
cnst_edge.clear();
for (int c = 0; c < cnst_tri.size(); ++c)
@@ -267,12 +335,59 @@ void dem2tin(const std::vector<double> &dem, double xmin, double xmax, double ym
}
// construct new triangles and add to out_tris
new_tri.clear();
for (int c = 0; c < cnst_edge.size(); ++c)
{
if (!is_collinear(cnst_edge[c].vert[0], cnst_edge[c].vert[1], tmp_vert)) // Do not create triangle if the vertexes are collinear
{
tmp_tri = new triangle(cnst_edge[c].vert[0], cnst_edge[c].vert[1], tmp_vert); // order the vertex anti-clock wise
out_tris.push_back(tmp_tri);
new_tri.push_back(tmp_tri);
}
}
// purge circumcircle triangles for all DEM data
for (int c = 0; c < cnst_tri.size(); ++c)
{
for (int i = 0; i < dem_grid.size(); ++i)
{
for (t_iter = dem_grid[i].circum_host.begin(); t_iter != dem_grid[i].circum_host.end(); )
{
if (cnst_tri[c] == *t_iter)
{
t_iter = dem_grid[i].circum_host.erase(t_iter);
break; // no need to search more
}
else t_iter++;
}
}
}
// loop all DEM data to update host and circumcircle triangles
for (int i = 0; i < dem_grid.size(); ++i)
{
for (int n = 0; n < new_tri.size(); ++n) // search in newly created triangles to find new host
{
if (new_tri[n]->bound_location(dem_grid[i].x, dem_grid[i].y))
{
dem_grid[i].host = new_tri[n];
break; // already found, no need to search more
}
}
}
// Find circum_host triangles for all DEM locations
for (int i = 0; i < dem_grid.size(); ++i)
{
for (int n = 0; n < new_tri.size(); ++n) // search in newly created triangles to find new circumcircle triangles
{
dist = (new_tri[n]->cx - dem_grid[i].x) * (new_tri[n]->cx - dem_grid[i].x)
+ (new_tri[n]->cy - dem_grid[i].y) * (new_tri[n]->cy - dem_grid[i].y);
if ((dist - new_tri[n]->cr) <= ZERO) // Points on the circumcircle are also included
{
dem_grid[i].circum_host.push_back(new_tri[n]);
// no beak here. There might be more than one triangle's circumcircle includes the DEM location
}
}
}
@@ -282,6 +397,7 @@ void dem2tin(const std::vector<double> &dem, double xmin, double xmax, double ym
tmp_tri = cnst_tri[c];
delete tmp_tri; tmp_tri = nullptr;
}
} while (now_maxi_err >= maxi_err);
return;