See scatteredinterpolant(): https://www.mathworks.com/help/releases/R2020a/matlab/ref/scatteredinterpolant.html to interpolate the 3D data points.
To visualize this 4D data, you can use slice() function. Something like this
Model = scatteredinterpolant(x1,x2,x3,x4);
x1g = linspace(min(x1), max(x1), 100);
x2g = linspace(min(x2), max(x2), 100);
x3g = linspace(min(x3), max(x3), 100);
[X1g, X2g, X3g] = meshgrid(x1g, x2g, x3g);
X4g = Model(X1g, X2g, X3g);
slice(X1g, X2g, X3g, X4g, [2 4], [2 4], [2])
