Make pinhole pose compatible with renderer (#361)

* Fix multiplier

* Add tutorial for DiffDRR to pinhole conversion

* Fix inverse projection

Author: eigenvivek

diffdrr/drr.py

@@ -283,9 +283,9 @@ def inverse_projection(
     pts: torch.Tensor,
 ):
     """Backproject points in pixel plane (2D) onto the image plane in world coordinates (3D)."""
-    # pts = pts.flip(-1)
+    pts[..., 1] = self.detector.height - pts[..., 1]
     if self.detector.reverse_x_axis:
-        pts[..., 1] = self.detector.width - pts[..., 1]
+        pts[..., 0] = self.detector.width - pts[..., 0]
     x = self.detector.sdd * torch.einsum(
         "ij, bnj -> bni",
         self.detector.intrinsic.inverse(),

diffdrr/utils.py

@@ -110,7 +110,7 @@ def get_pinhole_camera(
     pose = deepcopy(pose).to(device="cpu", dtype=dtype)
 
     # Make the intrinsic matrix (in pixels)
-    multiplier = -1 if drr.subject.orientation == "PA" else 1
+    multiplier = -1 if drr.subject.orientation == "AP" else 1
     fx = multiplier * drr.detector.sdd / drr.detector.delx
     fy = multiplier * drr.detector.sdd / drr.detector.dely
     u0 = drr.detector.x0 / drr.detector.delx + drr.detector.width / 2

notebooks/api/00_drr.ipynb

@@ -434,9 +434,9 @@
     "    pts: torch.Tensor,\n",
     "):\n",
     "    \"\"\"Backproject points in pixel plane (2D) onto the image plane in world coordinates (3D).\"\"\"\n",
-    "    # pts = pts.flip(-1)\n",
+    "    pts[..., 1] = self.detector.height - pts[..., 1]\n",
     "    if self.detector.reverse_x_axis:\n",
-    "        pts[..., 1] = self.detector.width - pts[..., 1]\n",
+    "        pts[..., 0] = self.detector.width - pts[..., 0]\n",
     "    x = self.detector.sdd * torch.einsum(\n",
     "        \"ij, bnj -> bni\",\n",
     "        self.detector.intrinsic.inverse(),\n",

notebooks/api/07_utils.ipynb

@@ -184,7 +184,7 @@
     "    pose = deepcopy(pose).to(device=\"cpu\", dtype=dtype)\n",
     "\n",
     "    # Make the intrinsic matrix (in pixels)\n",
-    "    multiplier = -1 if drr.subject.orientation == \"PA\" else 1\n",
+    "    multiplier = -1 if drr.subject.orientation == \"AP\" else 1\n",
     "    fx = multiplier * drr.detector.sdd / drr.detector.delx\n",
     "    fy = multiplier * drr.detector.sdd / drr.detector.dely\n",
     "    u0 = drr.detector.x0 / drr.detector.delx + drr.detector.width / 2\n",