Normals on front and back

This example validates that normals are handled such that both the front and back faces are lit. Further it validates the appearance of the normal lines material.

This shows a flattened cylinder, with normal lines sticking out both at the front and back faces.

from wgpu.gui.auto import WgpuCanvas, run
import pygfx as gfx
import pylinalg as la


renderer = gfx.WgpuRenderer(WgpuCanvas())
scene = gfx.Scene()

geo = gfx.cylinder_geometry(radial_segments=16, height_segments=3, open_ended=True)
ob1 = gfx.Mesh(
    geo,
    gfx.MeshPhongMaterial(color="#f00"),
)
ob2 = gfx.Mesh(
    geo,
    gfx.MeshNormalLinesMaterial(color="#0f0", line_length=0.4),
)
ob3 = gfx.Mesh(
    geo,
    gfx.MeshNormalLinesMaterial(color="#00f", line_length=-0.2),
)

ob1.local.position = (1, 0, 0)
ob1.local.rotation = la.quat_from_axis_angle((0, 1, 0), 1)
ob1.local.scale = (3, 1, 1)
scene.add(ob1.add(ob2, ob3))

scene.add(gfx.DirectionalLight(), gfx.AmbientLight())

camera = gfx.PerspectiveCamera(70, 1, depth_range=(0.1, 2000))
camera.local.z = 4.5

renderer.request_draw(lambda: renderer.render(scene, camera))


if __name__ == "__main__":
    print(__doc__)
    run()