Grid floor square lines

Hi ! I’m new in OpenFrameworks and OpenGL. I’m trying to draw a simple grid floor; something like this :

Where I can draw other 3D objects on the floor. I have already drawn an ofPlanePrimitive but I dont know how to draw square lines on it. I have some trouble with the coordinates of lines with ofDrawLine.
If someone have an example, it will be great.

Thanks for the help.

HI, just call

ofDrawGrid(float stepSize, size_t numberOfSteps, bool labels, bool x, bool y, bool z);

or

ofDrawGridPlane(float stepSize, size_t numberOfSteps, bool labels);

inside your draw() function;

Thank you !