Set ALICEVISION_SPHERE_DETECTION_MODEL variable

The `ALICEVISION_SPHERE_DETECTION` variable needs to be declared and set
using the installation path. If it is not, no node using it will be able
to work unless the users set this environment variable on their own.

Author: cbentejac

meshroom/__init__.py

@@ -120,6 +120,7 @@ def addToEnvPath(var, val, index=-1):
         qtPluginsDir = os.path.join(rootDir, "qtPlugins")
         sensorDBPath = os.path.join(aliceVisionShareDir, "cameraSensors.db")
         voctreePath = os.path.join(aliceVisionShareDir, "vlfeat_K80L3.SIFT.tree")
+        sphereDetectionModel = os.path.join(aliceVisionShareDir, "sphereDetection_Mask-RCNN.onnx")
 
         env = {
             'PATH': aliceVisionBinDir,
@@ -134,7 +135,8 @@ def addToEnvPath(var, val, index=-1):
         variables = {
             "ALICEVISION_ROOT": aliceVisionDir,
             "ALICEVISION_SENSOR_DB": sensorDBPath,
-            "ALICEVISION_VOCTREE": voctreePath
+            "ALICEVISION_VOCTREE": voctreePath,
+            "ALICEVISION_SPHERE_DETECTION_MODEL": sphereDetectionModel
         }
 
         for key, value in variables.items():