"isocaps" treats the threshold (1e-4) as a strict cutoff. Values below the threshold are entirely excluded from the isosurface generation. Since your data ranges from 0 to 1, setting the threshold to 1e-4 removes all zero values from the output. You can try one of the following solutions.
1. Adjust the threshold:
Instead of using a fixed threshold, you can calculate a threshold based on a percentage of your data range. (https://www.mathworks.com/help/matlab/ref/prctile.html)
threshold = prctile(trc(:), 1); % Find the 1st percentile value
fvc = isocaps(trc, threshold);
2. Use a different isosurfacing function:
"isosurface" takes an additional argument specifying the desired isosurface value(s). You can set this value to 0 to include all data points, including zeros.
