Interactive Art & Computational Design / Spring 2011

zDepth hack OpenNI

by chaotic*neutral @ 12:55 pm 9 February 2011

Hey guys I did a simple mod to the openNI library to allow you to get some z space depth information. This is just a quick hack to ofxTrackedUser.cpp

It takes the x position of the right shoulder, subtracts the difference in distance to the x position of the left shoulder, then draws a circle to the neck begin. The radius of the circle is mapped to the difference in distance between the two shoulders. SO IN SHORT: the further away the subject, the closer together the shoulder points, therefore the less distant between the two, in result a smaller head. Vice versa.

This will give you a head and z depth. Please feel free to improve it, as I just did this in a few minutes and thought I’d share.

NOTE: this is just a quick hack, if you turn shoulders (their x coordinates line up, it will shrink the head) Anyone have some other solutions?

 
#include "ofxTrackedUser.h"
#include "ofxDepthGenerator.h"
#include "ofxUserGenerator.h"
 
float xL;
float yL;
float xR;
float yR;
float zDEPTH;
 
ofxTrackedUser::ofxTrackedUser(
	 ofxUserGenerator* pUserGenerator
	,ofxDepthGenerator* pDepthGenerator
) 
:neck(XN_SKEL_HEAD, XN_SKEL_NECK)
 
// left arm + shoulder
,left_shoulder(XN_SKEL_NECK, XN_SKEL_LEFT_SHOULDER)
,left_upper_arm(XN_SKEL_LEFT_SHOULDER, XN_SKEL_LEFT_ELBOW)
,left_lower_arm(XN_SKEL_LEFT_ELBOW, XN_SKEL_LEFT_HAND)
 
// right arm + shoulder
,right_shoulder(XN_SKEL_NECK, XN_SKEL_RIGHT_SHOULDER)
,right_upper_arm(XN_SKEL_RIGHT_SHOULDER, XN_SKEL_RIGHT_ELBOW)
,right_lower_arm(XN_SKEL_RIGHT_ELBOW, XN_SKEL_RIGHT_HAND)
 
// upper torso
,left_upper_torso(XN_SKEL_LEFT_SHOULDER, XN_SKEL_TORSO)
,right_upper_torso(XN_SKEL_RIGHT_SHOULDER, XN_SKEL_TORSO)
 
// left lower torso + leg
,left_lower_torso(XN_SKEL_TORSO, XN_SKEL_LEFT_HIP)
,left_upper_leg(XN_SKEL_LEFT_HIP, XN_SKEL_LEFT_KNEE)
,left_lower_leg(XN_SKEL_LEFT_KNEE, XN_SKEL_LEFT_FOOT)
 
// right lower torso + leg
,right_lower_torso(XN_SKEL_TORSO, XN_SKEL_RIGHT_HIP)
,right_upper_leg(XN_SKEL_RIGHT_HIP, XN_SKEL_RIGHT_KNEE)
,right_lower_leg(XN_SKEL_RIGHT_KNEE, XN_SKEL_RIGHT_FOOT)
 
,hip(XN_SKEL_LEFT_HIP, XN_SKEL_RIGHT_HIP)
,user_generator(pUserGenerator)
,depth_generator(pDepthGenerator) 
,xn_user_generator(&user_generator->getXnUserGenerator())
,is_tracked(false)
{
}
 
void ofxTrackedUser::updateBonePositions() {
	updateLimb(neck);
 
	// left arm + shoulder
	updateLimb(left_shoulder);
	updateLimb(left_upper_arm);
	updateLimb(left_lower_arm);
 
	// right arm + shoulder
	updateLimb(right_shoulder);
	updateLimb(right_upper_arm);
	updateLimb(right_lower_arm);
 
	// upper torso
	updateLimb(left_upper_torso);
	updateLimb(right_upper_torso);
 
	// left lower torso + leg
	updateLimb(left_lower_torso);
	updateLimb(left_upper_leg);
	updateLimb(left_lower_leg);
 
	// right lower torso + leg
	updateLimb(right_lower_torso);
	updateLimb(right_upper_leg);
	updateLimb(right_lower_leg);
 
	updateLimb(hip);	
}
 
void ofxTrackedUser::updateLimb(ofxLimb& rLimb) {
	if(!xn_user_generator->GetSkeletonCap().IsTracking(id)) {
		//printf("Not tracking this user: %d\n", id);
		return;
	}
 
	XnSkeletonJointPosition a,b;
	xn_user_generator->GetSkeletonCap().GetSkeletonJointPosition(id, rLimb.start_joint, a);
	xn_user_generator->GetSkeletonCap().GetSkeletonJointPosition(id, rLimb.end_joint, b);
	if(a.fConfidence < 0.3f || b.fConfidence < 0.3f) {
		rLimb.found = false; 
		return;
	}
 
	XnPoint3D pos[2];
	pos[0] = a.position;
	pos[1] = b.position;
	depth_generator->getXnDepthGenerator()
		.ConvertRealWorldToProjective(2, pos, pos);
 
	rLimb.found = true;
	rLimb.begin.set(pos[0].X, pos[0].Y);
	rLimb.end.set(pos[1].X, pos[1].Y);
	ofSetColor(255, 0, 0);
	//ofCircle(pos[0].X, pos[0].Y, 5);
 
	float xL = left_upper_arm.begin.x;
	float yL = left_upper_arm.begin.y;
 
	float xR = right_upper_arm.begin.x;
	float yR = right_upper_arm.begin.y;
 
	zDEPTH = xR - xL;
 
}
 
void ofxTrackedUser::debugDraw() {
	neck.debugDraw();
 
	// left arm + shoulder
	left_shoulder.debugDraw();
	left_upper_arm.debugDraw();
	left_lower_arm.debugDraw();
 
	// right arm + shoulder
	right_shoulder.debugDraw();
	right_upper_arm.debugDraw();
	right_lower_arm.debugDraw();
 
	// upper torso
	left_upper_torso.debugDraw();
	right_upper_torso.debugDraw();
 
	// left lower torso + leg
	left_lower_torso.debugDraw();
	left_upper_leg.debugDraw();
	left_lower_leg.debugDraw();
 
	// right lower torso + leg
	right_lower_torso.debugDraw();
	right_upper_leg.debugDraw();
	right_lower_leg.debugDraw();
 
	hip.debugDraw();
	ofDrawBitmapString(ofToString((int)id),neck.begin.x+ 10, neck.begin.y);
 
	ofCircle(neck.begin.x, neck.begin.y, zDEPTH);
 
}

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