Octave Support for ISET3D-Tiny

README.md

@@ -20,3 +20,11 @@ To see some examples, have a look at the tutorial directory. If you want to read
 Note: This repository was formerly ISET3d-v4, pbrt2iset, and before that we relied on RenderToolbox4.
 
 ISET3d was originally developed in Brian Wandell's [Vistalab group](https://vistalab.stanford.edu/) at [Stanford University](stanford.edu), along with co-contributors from other research institutions and industry.
+
+## Octave Support
+- July 14, 2025: Ayush Jamdar.
+- New: A function `isOctave` tests if code is being run in Octave and uses modified code accordingly. 
+- The EXR readers come from OpenEXR and accept only the filename as input.
+- We still rely on `.mex` exr io functions but those are built using `mkoctfile`. See `isetcam/imgproc/openexr`
+- We have tested `isethdrsensor/scripts/fullSimulation.m` on examples from the ISET HDR dataset using Octave 6.4.0.
+- Refer to `isetcam/README.md` for Octave and Conda environment packages.

utilities/isOctave.m

@@ -0,0 +1,14 @@
+% Test if running in Octave
+
+% This function will be called whenever code differs between 
+% Matlab and Octave, with the goal to extend ISET support 
+
+function retval = isOctave
+  persistent cacheval;
+  if isempty (cacheval)
+    cacheval = (exist ("OCTAVE_VERSION", "builtin") > 0);
+  end
+  retval = cacheval;
+end
+
+

utilities/pbrt/pbrt-v4/piEXR2ISET.m

@@ -94,7 +94,7 @@
                 nn = nn+1;
             end
             try
-                % New format
+                % New format: exrread() either from Matlab or Openexr    
                 energy = exrread(inputFile,Channels = radianceChannels);
             catch
                 % keep the old format
@@ -109,16 +109,31 @@
 
         case {'depth', 'zdepth'}
             info = exrinfo(inputFile);
-            channelNames = info.ChannelInfo.Properties.RowNames;
-            if contains('P.X',channelNames)
-                % Modern naming for X,Y,Z coordinates
-                coordinates = exrread(inputFile,Channels=["P.X","P.Y","P.Z"]);
-            elseif contains('Px',channelNames)
-                % Historical naming
-                coordinates = exrread(inputFile,Channels=["Px","Py","Pz"]);
-            else
-                warning('No X,Y,Z channels found.  Returning.');
-                return;
+
+            if isOctave()
+                channelNames = info.channels;
+                if any(strcmp('P.X', channelNames))
+                    % Modern naming for X,Y,Z coordinates
+                    coordinates = exrread(inputFile);
+                elseif any(strcmp('Px', channelNames))
+                    % Historical naming
+                    coordinates = exrread(inputFile);
+                else
+                    warning('No X,Y,Z channels found.  Returning.');
+                    return;
+                end
+            else % Matlab
+                channelNames = info.ChannelInfo.Properties.RowNames;
+                if contains('P.X',channelNames)
+                    % Modern naming for X,Y,Z coordinates
+                    coordinates = exrread(inputFile,Channels=["P.X","P.Y","P.Z"]);
+                elseif contains('Px',channelNames)
+                    % Historical naming
+                    coordinates = exrread(inputFile,Channels=["Px","Py","Pz"]);
+                else
+                    warning('No X,Y,Z channels found.  Returning.');
+                    return;
+                end
             end
 
             if isequal(label{ii},'depth')

utilities/pbrt/pbrt-v4/piEXR2Mat.m

@@ -18,8 +18,15 @@
 % dockerWrapper Support, D. Cardinal, 2022
 %
 
+% Check if MATLAB exrread() is available
+% This function is available only in Matlab >= R2022b
+hasBuiltinExrread = false;
+if ~isOctave() && exist('isMATLABReleaseOlderThan', 'file') > 0
+    hasBuiltinExrread = ~isMATLABReleaseOlderThan('R2022b');
+end
+
 % tic
-if exist('isMATLABReleaseOlderThan','file') > 0 && ~isMATLABReleaseOlderThan('R2022b')
+if hasBuiltinExrread
     % Use Matlab builtin exrread from the image toolbox 
 
     % Matlab included exrread() in 2022b.  We included exread() in
@@ -48,9 +55,11 @@
     data = exrread(inputFile, Channels = channels);
     return;
 
-elseif isfile(fullfile(isetRootPath,'imgproc','openexr','exrread.m'))
-
-    % Use the exrread() from ISETCam.
+elseif isfile(fullfile(isetRootPath,'imgproc','openexr','exrreadchannels.mex'))
+    % If Matlab's exrread() isn't available, the user must be using 
+    % openexr's exrread() (either from older Matlab or Octave)
+    % In this case, the mex file should exist
+    % Note that this file reader uses arguments different from Matlab's
 
     if strcmpi(channelname,'radiance')
         channels = cell(1,31);
@@ -95,7 +104,7 @@
 
     if status
         disp(result);
-        error('EXR to Binary conversion failed.')
+        error('EXR to Binary conversion failed.');
     end
     allFiles = dir([indir,sprintf('/%s_*',fname)]);
     fileList = [];