Accessing point32 under geometry_msgs/PolygonStamped

asked 2017-07-19 01:36:04 -0600

BotLover
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Hi, I am new to ROS so excuse me for the silly doubt. There is a topic being published by a package, of type geometry_msgs/PolygonStamped. On executing rosmsg show this is what I got std_msgs/Header header uint32 seq time stamp string frame_id geometry_msgs/Polygon polygon geometry_msgs/Point32[] points float32 x float32 y float32 z Now I want to subscribe this topic and access Point x,y,z. How do I do it? Thanks in advance!

answered 2017-07-19 02:02:16 -0600

mgruhler

12390 ●32 ●193 ●173 https://github.com/mgruhler

Follow this tutorial, the Subscriber part, exchange std_msgs/String with geometry_msgs/PolygonStamped and then access with msg->polygon.points[i].x etc. Note that points is actually an std::vector so make sure to access this correctly.

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my callback function looks like void Callback(const PolygonStampedConstPtr& poly). Inside callback I am doing float u = poly->polygon.points.x; float v = poly->polygon.points.y;. But according to your answer what should my i be?

BotLover ( 2017-07-19 03:09:30 -0600 )edit

i depends on the vector. You have multiple elements, so it should be within the range of the number of polygons. You could also iterate over the full vector...

mgruhler ( 2017-07-19 05:49:56 -0600 )edit

It solved my problem. Thanks mig. I also want the time difference between consecutive calls to callback function. Can you tell how it would be done? I was thinking of difference b/w ros::time::now, but don't know how to use it!

BotLover ( 2017-07-19 12:03:34 -0600 )edit

please post a new question..

mgruhler ( 2017-07-20 01:14:40 -0600 )edit

Yaa got it!

BotLover ( 2017-07-22 15:28:29 -0600 )edit

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Accessing point32 under geometry_msgs/PolygonStamped

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