Viewport Selection: Vertex and Face Picking

[juanchuletas]

Labels: interaction raycasting
Estimate: 1 week

Context

Editing is useless without selection. This issue adds raycasting from the camera through the mouse cursor to identify the closest vertex or face in the active primitive.

Tasks

• Implement Ray { origin, direction } and Camera::generateRay(mouseX, mouseY, vpW, vpH) using inverse VP matrix
• Implement Primitive::raycastVertex(ray, threshold) - returns index of closest vertex within screen-space threshold
• Implement Primitive::raycastFace(ray) - Moller-Trumbore intersection, returns hit face index
• Add SelectionManager class: current mode (VERTEX / FACE), active primitive pointer, handleClick(ray) dispatcher
• Support additive selection (Shift+click) vs replace (plain click)
• Draw selected vertices as GL_POINTS overlay with highlight color
• Draw selected faces with a highlight color pass after main draw

Acceptance Criteria

• Clicking a vertex selects it, confirmed by visual highlight
• Clicking a face in face mode selects it
• Shift+click adds to selection without clearing existing
• Clicking empty space clears selection
• Selection works correctly after camera movement

Files

src/Modeling/SelectionManager.hpp  (new)
src/Modeling/SelectionManager.cpp  (new)
src/Camera/camera.hpp / .cpp
src/Geometries/primitives.hpp / .cpp
src/Shaders/selection.vert / .frag  (new)

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