For the project i am working on, i would like to make modifications to the engine, so it can run on dx9 GPUs, so almost anyone can play, even on a crappy laptop
There is no DX9 renderer and DX11 one need GPU with SM4.0 (DX10) at least, but theres OpenGL renderer, you can run it by adding -opengl option in ediotor path name, but im not sure if it will run in older gpu, you could try it. But dont expect great fps results, if anything you probably be only able to run things like Tappy Chicken and Swing Ninja which runs on less devoloped GPUs on mobile.
UE4 is made so you can have multiple renderers to chpose, so for DX9 you would need to write one. SM3.0 does not support SM4.0 and higher features so you would proably need to cut lot of things
And which OpenGL version is required?
Thats what im not sure about, there 2 operate options -opengl and opengl4 so i guess -opengl might be OpenGL 3.x
i was able to make ue4 run in dx10 mode on my terrible laptop with intel integrated graphics, but is slow.
yea DX10 works, i mentioned that in anwser