3D -> 2D on a Cylinder

gistfile1.txt

float theta, x, y, z;

theta = ofDegToRad(230); // 0 -> 360
x = cylRadius * cos(theta);
y = cylHeight * -0.4; // -h/2 -> h/2
z = cylRadius * sin(theta);
ofVec3f center = cam.worldToScreen( ofVec3f(x, y, z) );

cam.end();

ofDisableDepthTest();

ofPushMatrix();
ofTranslate(center);
ofRotateY( ofRadToDeg(sin(ofGetElapsedTimef())));

ofFill();
ofSetColor(ofColor::white, 100);
ofRect(0, 0, 0, 50, 30);

ofNoFill();
ofSetColor(ofColor::white, 255);
ofRect(0, 0, 0, 50, 30);

ofPopMatrix();