Subdivide a tetrahedron to a sphere with ofMesh in openFrameworks

subdivide-tetrahedron.cpp

#include "ofMain.h"
#include "ofAppGlutWindow.h"

class ofApp : public ofBaseApp {
public:
    
    ofMesh mesh;
    ofEasyCam cam;
    
    void setup() { 
        ofSetFrameRate(20);
        ofBackground(0);
        
        mesh.addVertex(ofVec3f(0,0,1));
        mesh.addVertex(ofVec3f(0,2*sqrt(2),-1)/3);
        mesh.addVertex(ofVec3f(-sqrt(6),-sqrt(2),-1)/3);
        mesh.addVertex(ofVec3f(sqrt(6),-sqrt(2),-1)/3);
        
        int numSubDivisions = 4;
        
        subdivideTriangles(mesh,0,1,2,numSubDivisions);
        subdivideTriangles(mesh,0,2,3,numSubDivisions);
        subdivideTriangles(mesh,0,3,1,numSubDivisions);
        subdivideTriangles(mesh,1,3,2,numSubDivisions);
    }
    
    void subdivideTriangles(ofMesh &mesh, int i0, int i1, int i2, int level) {
        if (level-->0) {
            mesh.addVertex(((mesh.getVertex(i0)+mesh.getVertex(i1))*.5).normalized());
            mesh.addVertex(((mesh.getVertex(i1)+mesh.getVertex(i2))*.5).normalized());
            mesh.addVertex(((mesh.getVertex(i2)+mesh.getVertex(i0))*.5).normalized());
            int i01=mesh.getNumVertices()-3;
            int i12=mesh.getNumVertices()-2;
            int i20=mesh.getNumVertices()-1;
            subdivideTriangles(mesh,i0,i01,i20,level);
            subdivideTriangles(mesh,i01,i1,i12,level);
            subdivideTriangles(mesh,i01,i12,i20,level);
            subdivideTriangles(mesh,i20,i12,i2,level);
        } else {
            mesh.addTriangle(i0,i1,i2);   
        }
    }
        
    void draw() {
        cam.begin();
        ofScale(100,100,100);
        mesh.drawWireframe();
        cam.end();
    }

};

int main() {
    ofAppGlutWindow window;
    window.setGlutDisplayString("rgba double depth alpha samples>=4"); 
    ofSetupOpenGL(&window, 500, 500, OF_WINDOW);
    ofRunApp(new ofApp());
}