I didn't find definite examples of his early paintings, so the images below include Orphist works in a Synthetic Cubist manner. Later on, he seems to have drifted towards a more conventional approach. But I might be wrong: some cityscapes below might have been pre-Cubist, because I have no dates for them.
What I can definitely state about Viana is that his color work is strikingly bold, yet often pleasing.
A blend of representational art (the still life part) with some modernist distortion (the simplified figures).
A hint of Cubism in the background: I don't have a date for this, but probably around 1914.
By 1916 he was into his Orphist-Cubist phase.
These are difficult to date -- could be either slightly before or after his bout with hard-core Modernism.
Probably not pre- Great War.
Again, probably painted sometime after the war.