Multi-Object Selection

Example demonstrating multi object selection using mouse events.

Hovering the mouse over a cube will highlight it with a bounding box. Clicking on a cube will select it. Double-clicking a cube will select all the items from that group (because the group has a double-click event handler). Holding shift will add to the selection.

This example keeps two materials, one for the default and one for the selected appearance. The low-level wgpu objects are associated with both the world object and the material. This means that swapping to a material that was already used (with that object) has zero overhead.

from functools import partial
from random import randint, random

from rendercanvas.auto import RenderCanvas, loop
import pygfx as gfx
import pylinalg as la


canvas = RenderCanvas()
renderer = gfx.renderers.WgpuRenderer(canvas)

camera = gfx.PerspectiveCamera(70, 16 / 9)
camera.local.z = 400
camera.show_pos(((0, 0, 0)))

controller = gfx.OrbitController(camera, register_events=renderer)

scene = gfx.Scene()
scene.add(gfx.AmbientLight(), camera.add(gfx.DirectionalLight()))

geometry = gfx.box_geometry(40, 40, 40)
default_material = gfx.MeshPhongMaterial(pick_write=True)
selected_material = gfx.MeshPhongMaterial(color="#FF0000", pick_write=True)
hover_material = gfx.MeshPhongMaterial(color="#FFAA00", pick_write=True)

outline = gfx.BoxHelper(thickness=3, color="#fa0")
scene.add(outline)

selected_objects = []


def set_material(material, obj):
    if isinstance(obj, gfx.Mesh):
        obj.material = material


def select(event):
    # when this event handler is invoked on non-leaf nodes of the
    # scene graph, event.target will still point to the leaf node that
    # originally triggered the event, so we use event.current_target
    # to get a reference to the node that is currently handling
    # the event, which can be a Mesh, a Group or None (the event root)
    obj = event.current_target

    # prevent propagation so we handle this event only at one
    # level in the hierarchy
    event.stop_propagation()

    # clear selection
    if selected_objects and "Shift" not in event.modifiers:
        while selected_objects:
            ob = selected_objects.pop()
            ob.traverse(partial(set_material, default_material))

    # if the background was clicked, we're done
    if isinstance(obj, gfx.Renderer):
        return

    # set selection (group or mesh)
    selected_objects.append(obj)
    obj.traverse(partial(set_material, selected_material))


def hover(event):
    obj = event.target
    if event.type == "pointer_enter":
        obj.add(outline)
        outline.set_transform_by_object(obj, "local", scale=1.1)
    elif outline.parent:
        outline.parent.remove(outline)


def random_rotation():
    return la.quat_from_euler(
        ((random() - 0.5) / 100, (random() - 0.5) / 100, (random() - 0.5) / 100)
    )


initialized = False


def animate():
    global initialized

    # Render with both materials, to initialize them.
    if not initialized:
        initialized = True
        scene.traverse(lambda obj: set_material(selected_material, obj))
        renderer.render(scene, camera)
        scene.traverse(lambda obj: set_material(default_material, obj))

    def random_rot(obj):
        if hasattr(obj, "random_rotation"):
            obj.local.rotation = la.quat_mul(obj.random_rotation, obj.local.rotation)

    scene.traverse(random_rot)
    renderer.render(scene, camera)
    canvas.request_draw()


if __name__ == "__main__":
    renderer.add_event_handler(select, "click")

    # Build up scene
    for _ in range(4):
        group = gfx.Group()
        group.random_rotation = random_rotation()
        group.add_event_handler(select, "double_click")
        scene.add(group)

        for _ in range(10):
            cube = gfx.Mesh(geometry, default_material)
            cube.local.position = (
                randint(-200, 200),
                randint(-200, 200),
                randint(-200, 200),
            )
            cube.random_rotation = random_rotation()
            cube.add_event_handler(select, "click")
            cube.add_event_handler(hover, "pointer_enter", "pointer_leave")
            group.add(cube)

    canvas.request_draw(animate)
    loop.run()