I am testing on my only Android device, the Amazon Fire TV Stick. The SOC Broadcom Capri 28155 was low-end a few years ago, but modern low-end smartphones have surpassed it in terms of performance and shader model capabilities, which makes it a good candidate to test the shader’s performance on. It is an Android TV compatible device that plugs into a TV HDMI port so it naturally lacks touch screen input. It is controlled with the simple remote for the Amazon Fire TV Stick that is basically like the standard Android TV remote with an extra Android menu button – the same amount of buttons as the Android TV Mini-Controller.
The device only supports up to 2K textures so that resolution was used for the surface texture. I wanted to tint the atmosphere using texture sampling in the vertex shader for performance but had to move it to the fragment shader since the tex2dlod function was not implemented in OpenGL ES 2.0.
I did not use very complicated controls for viewing the planet on Android TV. The remote D-pad is used to rotate the camera around the planet horizontally and vertically. I tried using the D-pad middle button to switch between rotating the camera and planet (so that the light could hit the Earth with different angles) but it was very confusing. I left these controls on the arrow keys for PC, but added a script I found online for more free WASD and mouse controls. The R and F keys can be used to go up and down as well for better 3D controls. For Android smartphone devices I added gyro controls for rotation and made the touch screen work as the mouse look-around controls, but I could not test that on an actual smartphone.
Mobile-friendly atmospheric scattering shader 