data_generation.markdown



Training data generation using Icosphere {#tutorial_data_generation}

Goal
In this tutorial you will learn how to

Conduct a point cloud of camera view on sphere.
Generate training images using 3D model.


Code
@include cnn_3dobj/samples/sphereview_data.cpp

Explanation
Here is the general structure of the program:


Create a window.
@code{.cpp}
viz::Viz3d myWindow("Coordinate Frame");
@endcode


Set window size as 64*64, we use this scale as default.
@code{.cpp}
myWindow.setWindowSize(Size(64,64));
@endcode


Add coordinate axes.
@code{.cpp}
myWindow.showWidget("Coordinate Widget", viz::WCoordinateSystem());
myWindow.setBackgroundColor(viz::Color::gray());
myWindow.spin();
@endcode


Create a Mesh widget, loading .ply models.
@code{.cpp}
viz::Mesh objmesh = viz::Mesh::load(plymodel);
@endcode


Get the center of the generated mesh widget, cause some .ply files.
@code{.cpp}
Point3d cam_focal_point = ViewSphere.getCenter(objmesh.cloud);
@endcode


Get the pose of the camera using makeCameraPoses.
@code{.cpp}
Affine3f cam_pose = viz::makeCameraPose(campos.at(pose)radius+cam_focal_point, cam_focal_point, cam_y_dirradius+cam_focal_point);
@endcode


Get the transformation matrix from camera coordinate system to global.
@code{.cpp}
Affine3f transform = viz::makeTransformToGlobal(Vec3f(1.0f,0.0f,0.0f), Vec3f(0.0f,1.0f,0.0f), Vec3f(0.0f,0.0f,1.0f), campos.at(pose));
viz::WMesh mesh_widget(objmesh);
@endcode


Save screen shot as images.
@code{.cpp}
myWindow.saveScreenshot(filename);
@endcode


Write images into binary files for further using in CNN training.
@code{.cpp}
ViewSphere.writeBinaryfile(filename, binaryPath, headerPath,(int)campos.size()num_class, label_class, (int)(campos.at(pose).x100), (int)(campos.at(pose).y100), (int)(campos.at(pose).z100), rgb_use);
@endcode


Results
Here is collection images created by this demo using 4 model.