Feature Picking

Table of Contents

• Usage
• MeshFeatureTracking Plugin
• MeshPaint Plugin

Usage

The RadiumEngine's Ra::Engine::Rendering::Renderer provides a picking method for Ra::Engine::Rendering::RenderObject selection.

The FeaturePicking feature enables to enhance the selection process up to selecting vertices, edges and triangles. The result of a Ra::Engine::Rendering::Renderer::PickingQuery is a Ra::Engine::Rendering::Renderer::PickingResult containing the following data:

• the picking mode: either Ra::Engine::Rendering::Renderer::RO, Ra::Engine::Rendering::Renderer::VERTEX, Ra::Engine::Rendering::Renderer::EDGE, Ra::Engine::Rendering::Renderer::TRIANGLE for simple feature selection and either Ra::Engine::Rendering::Renderer::C_VERTEX, Ra::Engine::Rendering::Renderer::C_EDGE or Ra::Engine::Rendering::Renderer::C_TRIANGLE for multiple selection;
• the index of the RO the selection is for ;
• the list of selected vertices indices given w.r.t. the corresponding selected element ;
• the list of selected element indices, either points for point clouds or triangles for meshes ;
• the list of selected edge's opposite vertex indices given w.r.t. the corresponding selected triangle.

Right after a selection, the Ra::Engine::Rendering::Renderer::PickingResult are stored in the Ra::Gui::PickingManager and the Ra::Gui::SelectionManager emits Ra::Gui::SelectionManager::currentChanged signal so that Plugins are told a new selection has been made.

The selection of a mesh feature is activated by holding a specific key while selecting the object (see the KeyMappingManager configuration file for those). Multiple selection activation can be activated/de-activated by pressing the corresponding key, which would also make a circle shape, representing the selection area, appear on the screen.

MeshFeatureTracking Plugin

The MeshFeatureTracking Plugin (Radium Official Plugins (https://gitlab.com/Storm-IRIT/radium-official-plugins)) is an example of how mesh features information can be displayed either through the Gui or as displayed objects. The SelectionManager's currentChanged signal is connected to the slot onCurrentChanged.

When this slot is triggered, the MeshFeatureTracking Plugin accesses the picking data through the PickingManager and updates both its information widget with the new picking data and the tracking sphere. The MeshFeatureTracking plugin also keeps its information widget updated at the end of each frame.

The MeshFeatureTracking plugin only manage simple feature selection. For an example on how to deal with multiple selection, please see the MeshPaint Plugin.

MeshPaint Plugin

The MeshPaint Plugin (Radium Official Plugins (https://gitlab.com/Storm-IRIT/radium-official-plugins)) is an example of how to use mesh feature multi-selection. Here again, the SelectionManager's currentChanged signal is connected to the slot onCurrentChanged.

When this slot is triggered, and if the painting is enabled, the MeshPaint Plugin directly changes the render color of the vertices corresponding to the current picking data.