FIX: improved billboard sphere implementation

- Fixed typo and sphere intersection calculations
- Cleaned up sphere function and tests
- Better array handling and documentation

Author: m-agour

fury/actor/curved.py

@@ -67,7 +67,6 @@ def sphere(
         Whether to create a smooth sphere or a faceted sphere.
     impostor : bool, optional
         Render spheres as billboard impostors instead of geometry when ``True``.
-        Defaults to ``False``.
 
     Returns
     -------
@@ -115,7 +114,7 @@ def sphere(
         obj.billboard_radii = radii_arr.copy()
         return obj
 
-    scales = radii
+    scales = radii_arr
     directions = (1, 0, 0)
 
     vertices, faces = fp.prim_sphere(phi=phi, theta=theta)
@@ -131,8 +130,6 @@ def sphere(
         smooth=smooth,
         enable_picking=enable_picking,
     )
-    obj.billboard_radii = radii_arr.copy()
-    obj.billboard_mode = "mesh"
     return obj
 
 

fury/tests/test_billboard.py

@@ -140,8 +140,6 @@ def test_billboard_sphere(interactive: bool = False):
 
     assert isinstance(mesh_spheres.material, MeshPhongMaterial)
     assert not isinstance(mesh_spheres.material, BillboardSphereMaterial)
-    npt.assert_allclose(mesh_spheres.billboard_radii, radii)
-    assert getattr(mesh_spheres, "billboard_mode", None) == "mesh"
 
     impostor_spheres = actor.sphere(
         centers,

fury/wgsl/billboard_sphere_render.wgsl

@@ -106,15 +106,22 @@ fn fs_main(varyings: Varyings, @builtin(front_facing) is_front: bool) -> Fragmen
     let oc = ray_origin - center;
     let b = dot(ray_dir, oc);
     let c = dot(oc, oc) - radius * radius;
-    let discriminant = b * b - c;
+    var discriminant = b * b - c;
     if (discriminant < 0.0) {
-        discard;
+        if (discriminant > -1e-4) {
+            discriminant = 0.0;
+        } else {
+            discard;
+        }
     }
     let sqrt_disc = sqrt(discriminant);
     var t = -b - sqrt_disc;
     if (t < 0.0) {
         t = -b + sqrt_disc;
     }
+    if (t < 0.0) {
+        discard;
+    }
     let world_pos = ray_origin + ray_dir * t;
     var world_normal = normalize(world_pos - center);
     if (!is_front) {
@@ -132,7 +139,7 @@ fn fs_main(varyings: Varyings, @builtin(front_facing) is_front: bool) -> Fragmen
     diffuse_color.a *= u_material.opacity * mask;
     do_alpha_test(diffuse_color.a);
 
-    let physical_albeido = diffuse_color.rgb;
+    let physical_albedo = diffuse_color.rgb;
     let specular_strength = 1.0;
 
     var reflected_light: ReflectedLight = ReflectedLight(
@@ -148,7 +155,7 @@ fn fs_main(varyings: Varyings, @builtin(front_facing) is_front: bool) -> Fragmen
     geometry.view_dir = view_dir;
 
     var material: BlinnPhongMaterial;
-    material.diffuse_color = physical_albeido;
+    material.diffuse_color = physical_albedo;
     material.specular_color = srgb2physical(u_material.specular_color.rgb);
     material.specular_shininess = u_material.shininess;
     material.specular_strength = specular_strength;
@@ -170,7 +177,7 @@ fn fs_main(varyings: Varyings, @builtin(front_facing) is_front: bool) -> Fragmen
     if (all(physical_color == vec3<f32>(0.0))) {
         let fallback_light = normalize(vec3<f32>(0.3, 0.5, 0.8));
         let fallback_diffuse = max(dot(world_normal, fallback_light), 0.0);
-        physical_color = physical_albeido * clamp(0.3 + 0.7 * fallback_diffuse, 0.0, 1.0);
+        physical_color = physical_albedo * clamp(0.3 + 0.7 * fallback_diffuse, 0.0, 1.0);
     }
 
     var out: FragmentOutput;