[test] [example] Add test and video generator for cornell box. (#4045)

python/taichi/examples/rendering/cornell_box.py

@@ -491,18 +491,23 @@ def tonemap(accumulated: ti.f32):
                                           100.0)
 
 
-gui = ti.GUI('Cornell Box', res, fast_gui=True)
-gui.fps_limit = 300
-last_t = time.time()
-i = 0
-while gui.running:
-    render()
-    interval = 10
-    if i % interval == 0:
-        tonemap(i)
-        print("{:.2f} samples/s ({} iters)".format(
-            interval / (time.time() - last_t), i))
-        last_t = time.time()
-        gui.set_image(tonemapped_buffer)
-        gui.show()
-    i += 1
+def main():
+    gui = ti.GUI('Cornell Box', res, fast_gui=True)
+    gui.fps_limit = 300
+    last_t = time.time()
+    i = 0
+    while gui.running:
+        render()
+        interval = 10
+        if i % interval == 0:
+            tonemap(i)
+            print("{:.2f} samples/s ({} iters)".format(
+                interval / (time.time() - last_t), i))
+            last_t = time.time()
+            gui.set_image(tonemapped_buffer)
+            gui.show()
+        i += 1
+
+
+if __name__ == '__main__':
+    main()

tests/python/examples/rendering/test_cornell_box.py

@@ -0,0 +1,43 @@
+import argparse
+
+import taichi as ti
+
+FRAMES = 200
+
+
+def test_cornell_box():
+    from taichi.examples.rendering.cornell_box import render, tonemap
+    for i in range(FRAMES):
+        render()
+        interval = 10
+        if i % interval == 0:
+            tonemap(i)
+
+
+def video_cornell_box(result_dir):
+    from taichi.examples.rendering.cornell_box import (render, tonemap,
+                                                       tonemapped_buffer)
+    video_manager = ti.VideoManager(output_dir=result_dir,
+                                    framerate=24,
+                                    automatic_build=False)
+    gui = ti.GUI("Taichi Cornell Box",
+                 res=800,
+                 background_color=0x112F41,
+                 show_gui=False)
+    for i in range(FRAMES):
+        render()
+        interval = 10
+        if i % interval == 0:
+            tonemap(i)
+
+        gui.set_image(tonemapped_buffer)
+        video_manager.write_frame(gui.get_image())
+        gui.clear()
+    video_manager.make_video(mp4=True, gif=False)
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(description='Generate cornell_box video')
+    parser.add_argument('output_directory',
+                        help='output directory of generated video')
+    video_cornell_box(parser.parse_args().output_directory)