Adding Light.py

src/PythonicAPI.md

@@ -498,6 +498,7 @@ This section includes ?vtkUnstructuredGrid?.
 
 | Example Name | Description | Image |
 | -------------- | ------------- | ------- |
+[Light](/PythonicAPI/Lighting/Light) | Add a directional light to a scene.
 [ShadowsLightsDemo](/PythonicAPI/Visualization/ShadowsLightsDemo) | Show lights casting shadows.
 
 ## Texture Mapping

src/PythonicAPI/Lighting/Light.py

+#!/usr/bin/env python3
+
+from dataclasses import dataclass
+
+# noinspection PyUnresolvedReferences
+import vtkmodules.vtkInteractionStyle
+# noinspection PyUnresolvedReferences
+import vtkmodules.vtkRenderingOpenGL2
+# noinspection PyUnresolvedReferences
+import vtkmodules.vtkRenderingUI
+from vtkmodules.vtkCommonColor import vtkNamedColors
+from vtkmodules.vtkFiltersSources import vtkSphereSource, vtkPlaneSource
+from vtkmodules.vtkRenderingCore import (
+    vtkActor,
+    vtkPolyDataMapper,
+    vtkRenderWindow,
+    vtkRenderWindowInteractor,
+    vtkRenderer, vtkLight, vtkLightActor
+)
+
+
+def main():
+    colors = vtkNamedColors()
+
+    renderer = vtkRenderer(background=colors.GetColor3d('Black'), background2=colors.GetColor3d('Silver'),
+                           gradient_background=True, automatic_light_creation=True)
+
+    # Create a light.
+    light_position = (0, 0, 1)
+    light_focal_point = (0, 0, 0)
+
+    light = vtkLight(light_type=Light.LightType.VTK_LIGHT_TYPE_SCENE_LIGHT,
+                     position=light_position, positional=True,
+                     focal_point=light_focal_point, cone_angle=10,
+                     diffuse_color=colors.GetColor3d('Red'),
+                     ambient_color=colors.GetColor3d('Green'),
+                     specular_color=colors.GetColor3d('Blue')
+                     )
+    original_lights = renderer.lights
+    print(f'Originally there {lights_txt(original_lights)}')
+
+    # Display where the light is.
+    light_actor = vtkLightActor(light=light)
+    renderer.AddViewProp(light_actor)
+
+    # Display where the light is focused.
+    light_focal_point_sphere = vtkSphereSource(center=light_focal_point, radius=0.1)
+    light_focal_point_mapper = vtkPolyDataMapper()
+    light_focal_point_sphere >> light_focal_point_mapper
+    light_focal_point_actor = vtkActor(mapper=light_focal_point_mapper)
+    light_focal_point_actor.property.color = colors.GetColor3d('Yellow')
+    renderer.AddViewProp(light_focal_point_actor)
+
+    # Create a plane for the light to shine on.
+    plane_source = vtkPlaneSource(resolution=(100, 100))
+    plane_mapper = vtkPolyDataMapper(input_data=plane_source.update().output)
+    plane_actor = vtkActor(mapper=plane_mapper)
+    renderer.AddActor(plane_actor)
+
+    ren_win = vtkRenderWindow(window_name='Light')
+    ren_win.AddRenderer(renderer)
+    iren = vtkRenderWindowInteractor()
+    iren.render_window = ren_win
+
+    ren_win.Render()
+    print(f'Now there {lights_txt(original_lights)}')
+    renderer.AddLight(light)  # We must do this after ren_win.Render()
+    print(f'Now there {lights_txt(original_lights)}')
+
+    camera = renderer.active_camera
+    camera.position = (-2.17199, -2.50774, 2.18)
+    camera.focal_point = (-0.144661, -0.146372, 0.180482)
+    camera.view_up = (0.0157883, 0.638203, 0.769706)
+    camera.SetDistance(3.69921)
+    camera.SetClippingRange(1.76133, 6.14753)
+
+    iren.Start()
+
+
+def lights_txt(light_collection):
+    number_of_lights = light_collection.number_of_items
+    match number_of_lights:
+        case 0:
+            return f'are no lights.'
+        case 1:
+            return f'is one light.'
+        case _:
+            return f'are {number_of_lights} lights.'
+
+
+@dataclass(frozen=True)
+class Light:
+    @dataclass(frozen=True)
+    class LightType:
+        VTK_LIGHT_TYPE_HEADLIGHT: int = 1
+        VTK_LIGHT_TYPE_CAMERA_LIGHT: int = 2
+        VTK_LIGHT_TYPE_SCENE_LIGHT: int = 3
+
+
+if __name__ == '__main__':
+    main()