examples and docs.

Summary: This diff updates the documentation and tutorials with information about the new pulsar backend. For more information about the pulsar backend, see the release notes and the paper (https://arxiv.org/abs/2004.07484). For information on how to use the backend, see the point cloud rendering notebook and the examples in the folder docs/examples.

Reviewed By: nikhilaravi

Differential Revision: D24498129

fbshipit-source-id: e312b0169a72b13590df6e4db36bfe6190d742f9

docs/examples/pulsar_basic.py

@@ -5,6 +5,7 @@ This example demonstrates the most trivial, direct interface of the pulsar
 sphere renderer. It renders and saves an image with 10 random spheres.
 Output: basic.png.
 """
+import math
 from os import path
 
 import imageio
@@ -12,11 +13,15 @@ import torch
 from pytorch3d.renderer.points.pulsar import Renderer
 
 
+torch.manual_seed(1)
+
 n_points = 10
 width = 1_000
 height = 1_000
 device = torch.device("cuda")
-renderer = Renderer(width, height, n_points).to(device)
+# The PyTorch3D system is right handed; in pulsar you can choose the handedness.
+# For easy reproducibility we use a right handed coordinate system here.
+renderer = Renderer(width, height, n_points, right_handed_system=True).to(device)
 # Generate sample data.
 vert_pos = torch.rand(n_points, 3, dtype=torch.float32, device=device) * 10.0
 vert_pos[:, 2] += 25.0
@@ -29,7 +34,7 @@ cam_params = torch.tensor(
         0.0,
         0.0,  # Position 0, 0, 0 (x, y, z).
         0.0,
-        0.0,
+        math.pi,  # Because of the right handed system, the camera must look 'back'.
         0.0,  # Rotation 0, 0, 0 (in axis-angle format).
         5.0,  # Focal length in world size.
         2.0,  # Sensor size in world size.