Apps with 'Realistic viewport' feature
Blender is the free and open-source 3D creation suite. It supports the entirety of the 3D pipeline—modeling, rigging, animation, simulation, rendering, compositing, video editing, and motion tracking.
AwesomeBump is an open source program designed to generate normal, height, specular or ambient occlusion textures from a single image.
A free tool for app and website developers to get live viewport dimensions of any device.