Add distortion to renders

Summary:
Apply fisheye62 distortion to HQLP camera renders.

Visualization of results. 4 rows are in order: HMC, drtk render, pixel render, pinhole img.

https://www.internalfb.com/manifold/explorer/codec-avatars-scratch/tree/hmc_nvs/20240516_rosetta_nearfield/runs/TEST_run_hqlp_rosetta_render_ojwang_v0719_002/dome_hmc_nvs_render/MLU130_20220509--0000_codec/vrs_comparison/000002__MLU130-brows_lowered-2022-05-09-16-08-12.png

Debug distortion document, tracked the work: https://docs.google.com/document/d/1nSnFMrGWXVoICDEstpL9JZAnRtiuSMnWjnfGDzIfrNE/edit?pli=1

Reviewed By: euclid1767

Differential Revision: D58825272

fbshipit-source-id: 463f8c60014bd9cde898d72875bec49ffc75e453

drtk/utils/projection.py

@@ -9,7 +9,11 @@ from typing import Optional, Sequence, Set, Tuple, Union
 import numpy as np
 import torch as th
 
-DISTORTION_MODES: Set[Optional[str]] = {None, "radial-tangential", "fisheye"}
+DISTORTION_MODES: Set[Optional[str]] = {
+    None,
+    "radial-tangential",
+    "fisheye",
+}
 
 
 def project_pinhole(
@@ -163,7 +167,7 @@ def project_fisheye_distort_62(
     v_cam:      N x V x 3
     focal:      N x 2 x 2
     princpt:    N x 2
-    D:          N x 4
+    D:          N x 8
     fov:        N x 1
     """
 
@@ -171,6 +175,11 @@ def project_fisheye_distort_62(
     # a more readible version: https://euratom-software.github.io/calcam/html/intro_theory.html
     if fov is None:
         with th.no_grad():
+            # TODO: bug.
+            # Fisheye62 uses 8 parameters, and the first 4 can be used
+            # by the same FOV estimation equation as fisheye distortion.
+            # However, the code takes the coeffs at indices -4, -3, -2,
+            # -1: which take the last 4 values, instead of the first 4.
             fov = estimate_fisheye_fov(D)
 
     z = v_cam[:, :, 2:3]