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Catmull–Clark subdivision surface: Difference between revisions

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Catmull–Clark subdivision surface (view source)

Revision as of 14:56, 24 May 2024

11,397 bytes added ,  1 month ago
New post.
m (Rewritten code to deal with holes in the surface.)
(New post.)
 
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return nm;
}</syntaxhighlight>
 
=={{header|C++}}==
<syntaxhighlight lang="c++">
#include <algorithm>
#include <cstdint>
#include <iomanip>
#include <iostream>
#include <map>
#include <set>
#include <sstream>
#include <string>
#include <vector>
 
// A point of the current Catmull-Clark surface.
class Point {
public:
Point() : x(0.0), y(0.0), z(0.0) { }
Point(const double& aX, const double& aY, const double& aZ) : x(aX), y(aY), z(aZ) { }
 
Point add(const Point& other) const {
return Point(x + other.x, y + other.y, z + other.z);
}
 
Point multiply(const double& factor) const {
return Point(x * factor, y * factor, z * factor);
}
 
Point divide(const double& factor) const {
return multiply(1.0 / factor);
}
 
bool operator<(const Point& other) const {
return ( x < other.x ) || ( ( x == other.x && y < other.y ) )
|| ( x == other.x && y == other.y && z < other.z );
}
 
bool operator==(const Point& other) const {
return x == other.x && y == other.y && z == other.z;
}
 
Point& operator=(const Point& other) {
if ( *this != other ) {
x = other.x; y = other.y; z = other.z;
}
return *this;
}
 
std::string to_string() const {
return "(" + format(x) + ", " + format(y) + ", " + format(z) + ")";
}
 
private:
std::string format(const double& value) const {
std::stringstream stream;
stream << std::fixed << std::setprecision(3) << value;
return ( value >= 0 ) ? " " + stream.str() : stream.str();
}
 
double x, y, z;
};
 
// Return the centroid point of the given vector of points.
Point centroid(const std::vector<Point>& points) {
Point sum;
for ( const Point& point : points ) {
sum = sum.add(point);
}
return sum.divide(points.size());
}
 
// An edge of the current Catmull-Clark surface.
class Edge {
public:
Edge(Point aBegin, Point aEnd) {
if ( aEnd < aBegin ) {
std::swap(aBegin, aEnd);
}
begin = aBegin; end = aEnd;
 
mid_edge = centroid({ begin, end });
hole_edge = false;
}
 
bool contains(const Point& point) const {
return point == begin || point == end;
}
 
bool operator<(const Edge other) const {
return ( begin < other.begin ) || ( begin == other.begin && end < other.end );
}
 
bool operator==(const Edge& other) const {
return contains(other.begin) && contains(other.end);
}
 
bool hole_edge;
Point begin, end, mid_edge, edge_point;
};
 
// A face of the current Catmull-Clark surface.
class Face {
public:
Face(std::vector<Point> aVertices) {
vertices = aVertices;
face_point = centroid(vertices);
 
for ( uint64_t i = 0; i < vertices.size() - 1; ++i ) {
edges.emplace_back(Edge(vertices[i], vertices[i + 1]));
}
edges.emplace_back(Edge(vertices.back(), vertices.front()));
}
 
bool contains(const Point& vertex) const {
return std::find(vertices.begin(), vertices.end(), vertex) != vertices.end();
}
 
bool contains(Edge edge) const {
return contains(edge.begin) && contains(edge.end);
}
 
std::string toString() const {
std::string result = "Face: ";
for ( uint64_t i = 0; i < vertices.size() - 1; ++i ) {
result += vertices[i].to_string() + ", ";
}
return result + vertices.back().to_string();
}
 
std::vector<Point> vertices;
std::vector<Edge> edges;
Point face_point;
};
 
// Return a map containing, for each vertex,
// the new vertex created by the current iteration of the Catmull-Clark surface subdivision algorithm.
std::map<Point, Point> next_vertices(const std::vector<Edge>& edges, const std::vector<Face>& faces) {
std::map<Point, Point> next_vertices = { };
std::set<Point> vertices = { };
for ( const Face& face : faces ) {
for ( const Point& vertex : face.vertices ) {
vertices.emplace(vertex);
}
}
 
for ( const Point& vertex : vertices ) {
std::vector<Face> faces_for_vertex = { };
for ( const Face& face : faces ) {
if ( face.contains(vertex) ) {
faces_for_vertex.emplace_back(face);
}
}
 
std::set<Edge> edges_for_vertex = { };
for ( const Edge& edge : edges ) {
if ( edge.contains(vertex) ) {
edges_for_vertex.emplace(edge);
}
}
 
if ( faces_for_vertex.size() != edges_for_vertex.size() ) {
std::vector<Point> mid_edge_of_hole_edges = { };
for ( const Edge& edge : edges_for_vertex ) {
if ( edge.hole_edge ) {
mid_edge_of_hole_edges.emplace_back(edge.mid_edge);
}
}
mid_edge_of_hole_edges.emplace_back(vertex);
next_vertices[vertex] = centroid(mid_edge_of_hole_edges);
} else {
const uint64_t face_count = faces_for_vertex.size();
const double multiple_1 = static_cast<double>(( face_count - 3 ) / face_count);
const double multiple_2 = 1.0 / face_count;
const double multiple_3 = 2.0 / face_count;
 
Point next_vertex_1 = vertex.multiply(multiple_1);
std::vector<Point> face_points = { };
for ( const Face& face : faces_for_vertex ) {
face_points.emplace_back(face.face_point);
}
Point next_vertex_2 = centroid(face_points).multiply(multiple_2);
std::vector<Point> mid_edges = { };
for ( const Edge& edge : edges_for_vertex ) {
mid_edges.emplace_back(edge.mid_edge);
}
Point next_vertex_3 = centroid(mid_edges).multiply(multiple_3);
Point next_vertex_4 = next_vertex_1.add(next_vertex_2);
 
next_vertices[vertex] = next_vertex_4.add(next_vertex_3);
}
}
return next_vertices;
}
 
// The Catmull-Clarke surface subdivision algorithm.
std::vector<Face> catmull_clark_surface_subdivision(std::vector<Face>& faces) {
// Determine, for each edge, whether or not it is an edge of a hole, and set its edge point accordingly.
for ( Face& face : faces ) {
for ( Edge& edge : face.edges ) {
std::vector<Point> face_points_for_edge = { };
for ( const Face& search_face : faces ) {
if ( search_face.contains(edge) ) {
face_points_for_edge.emplace_back(search_face.face_point);
}
}
 
if ( face_points_for_edge.size() == 2 ) {
edge.hole_edge = false;
edge.edge_point = centroid({ edge.mid_edge, centroid(face_points_for_edge) });
} else {
edge.hole_edge = true;
edge.edge_point = edge.mid_edge;
}
}
}
 
std::vector<Edge> edges = { };
for ( const Face& face : faces ) {
for ( const Edge& edge : face.edges ) {
edges.emplace_back(edge);
}
}
std::map<Point, Point> next_vertex_map = next_vertices(edges, faces);
 
std::vector<Face> next_faces = { };
for ( Face face : faces ) { // The face may contain any number of points
if ( face.vertices.size() >= 3 ) { // A face with 2 or fewer points does not contribute to the surface
Point face_point = face.face_point;
for ( uint64_t i = 0; i < face.vertices.size(); ++i ) {
next_faces.emplace_back(Face({
next_vertex_map[face.vertices[i]],
face.edges[i].edge_point,
face_point,
face.edges[( i - 1 + face.vertices.size() ) % face.vertices.size()].edge_point}));
}
}
}
return next_faces;
}
 
// Display the current Catmull-Clark surface on the console.
void displaySurface(const std::vector<Face> faces) {
std::cout << "Surface {" << std::endl;
for ( const Face& face : faces ) {
std::cout << face.toString() << std::endl;
}
std::cout << "}" << std::endl << std::endl;
}
 
int main() {
std::vector<Face> faces = {
Face({ Point(-1.0, 1.0, 1.0), Point(-1.0, -1.0, 1.0), Point( 1.0, -1.0, 1.0), Point( 1.0, 1.0, 1.0) }),
Face({ Point( 1.0, 1.0, 1.0), Point( 1.0, -1.0, 1.0), Point( 1.0, -1.0, -1.0), Point( 1.0, 1.0, -1.0) }),
Face({ Point( 1.0, 1.0, -1.0), Point( 1.0, -1.0, -1.0), Point(-1.0, -1.0, -1.0), Point(-1.0, 1.0, -1.0) }),
Face({ Point(-1.0, 1.0, -1.0), Point(-1.0, 1.0, 1.0), Point( 1.0, 1.0, 1.0), Point( 1.0, 1.0, -1.0) }),
Face({ Point(-1.0, 1.0, -1.0), Point(-1.0, -1.0, -1.0), Point(-1.0, -1.0, 1.0), Point(-1.0, 1.0, 1.0) }),
Face({ Point(-1.0, -1.0, -1.0), Point(-1.0, -1.0, 1.0), Point( 1.0, -1.0, 1.0), Point( 1.0, -1.0, -1.0) })};
 
displaySurface(faces);
const uint32_t iterations = 1;
for ( uint32_t i = 0; i < iterations; ++i ) {
faces = catmull_clark_surface_subdivision(faces);
}
displaySurface(faces);
}
</syntaxhighlight>
{{ out }}
<pre>
Surface {
Face: (-1.000, 1.000, 1.000), (-1.000, -1.000, 1.000), ( 1.000, -1.000, 1.000), ( 1.000, 1.000, 1.000)
Face: ( 1.000, 1.000, 1.000), ( 1.000, -1.000, 1.000), ( 1.000, -1.000, -1.000), ( 1.000, 1.000, -1.000)
Face: ( 1.000, 1.000, -1.000), ( 1.000, -1.000, -1.000), (-1.000, -1.000, -1.000), (-1.000, 1.000, -1.000)
Face: (-1.000, 1.000, -1.000), (-1.000, 1.000, 1.000), ( 1.000, 1.000, 1.000), ( 1.000, 1.000, -1.000)
Face: (-1.000, 1.000, -1.000), (-1.000, -1.000, -1.000), (-1.000, -1.000, 1.000), (-1.000, 1.000, 1.000)
Face: (-1.000, -1.000, -1.000), (-1.000, -1.000, 1.000), ( 1.000, -1.000, 1.000), ( 1.000, -1.000, -1.000)
}
 
Surface {
Face: (-0.556, 0.556, 0.556), (-0.750, 0.000, 0.750), ( 0.000, 0.000, 1.000), ( 0.000, 0.750, 0.750)
Face: (-0.556, -0.556, 0.556), ( 0.000, -0.750, 0.750), ( 0.000, 0.000, 1.000), (-0.750, 0.000, 0.750)
Face: ( 0.556, -0.556, 0.556), ( 0.750, 0.000, 0.750), ( 0.000, 0.000, 1.000), ( 0.000, -0.750, 0.750)
Face: ( 0.556, 0.556, 0.556), ( 0.000, 0.750, 0.750), ( 0.000, 0.000, 1.000), ( 0.750, 0.000, 0.750)
Face: ( 0.556, 0.556, 0.556), ( 0.750, 0.000, 0.750), ( 1.000, 0.000, 0.000), ( 0.750, 0.750, 0.000)
Face: ( 0.556, -0.556, 0.556), ( 0.750, -0.750, 0.000), ( 1.000, 0.000, 0.000), ( 0.750, 0.000, 0.750)
Face: ( 0.556, -0.556, -0.556), ( 0.750, 0.000, -0.750), ( 1.000, 0.000, 0.000), ( 0.750, -0.750, 0.000)
Face: ( 0.556, 0.556, -0.556), ( 0.750, 0.750, 0.000), ( 1.000, 0.000, 0.000), ( 0.750, 0.000, -0.750)
Face: ( 0.556, 0.556, -0.556), ( 0.750, 0.000, -0.750), ( 0.000, 0.000, -1.000), ( 0.000, 0.750, -0.750)
Face: ( 0.556, -0.556, -0.556), ( 0.000, -0.750, -0.750), ( 0.000, 0.000, -1.000), ( 0.750, 0.000, -0.750)
Face: (-0.556, -0.556, -0.556), (-0.750, 0.000, -0.750), ( 0.000, 0.000, -1.000), ( 0.000, -0.750, -0.750)
Face: (-0.556, 0.556, -0.556), ( 0.000, 0.750, -0.750), ( 0.000, 0.000, -1.000), (-0.750, 0.000, -0.750)
Face: (-0.556, 0.556, -0.556), (-0.750, 0.750, 0.000), ( 0.000, 1.000, 0.000), ( 0.000, 0.750, -0.750)
Face: (-0.556, 0.556, 0.556), ( 0.000, 0.750, 0.750), ( 0.000, 1.000, 0.000), (-0.750, 0.750, 0.000)
Face: ( 0.556, 0.556, 0.556), ( 0.750, 0.750, 0.000), ( 0.000, 1.000, 0.000), ( 0.000, 0.750, 0.750)
Face: ( 0.556, 0.556, -0.556), ( 0.000, 0.750, -0.750), ( 0.000, 1.000, 0.000), ( 0.750, 0.750, 0.000)
Face: (-0.556, 0.556, -0.556), (-0.750, 0.000, -0.750), (-1.000, 0.000, 0.000), (-0.750, 0.750, 0.000)
Face: (-0.556, -0.556, -0.556), (-0.750, -0.750, 0.000), (-1.000, 0.000, 0.000), (-0.750, 0.000, -0.750)
Face: (-0.556, -0.556, 0.556), (-0.750, 0.000, 0.750), (-1.000, 0.000, 0.000), (-0.750, -0.750, 0.000)
Face: (-0.556, 0.556, 0.556), (-0.750, 0.750, 0.000), (-1.000, 0.000, 0.000), (-0.750, 0.000, 0.750)
Face: (-0.556, -0.556, -0.556), (-0.750, -0.750, 0.000), ( 0.000, -1.000, 0.000), ( 0.000, -0.750, -0.750)
Face: (-0.556, -0.556, 0.556), ( 0.000, -0.750, 0.750), ( 0.000, -1.000, 0.000), (-0.750, -0.750, 0.000)
Face: ( 0.556, -0.556, 0.556), ( 0.750, -0.750, 0.000), ( 0.000, -1.000, 0.000), ( 0.000, -0.750, 0.750)
Face: ( 0.556, -0.556, -0.556), ( 0.000, -0.750, -0.750), ( 0.000, -1.000, 0.000), ( 0.750, -0.750, 0.000)
}
</pre>
 
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