AE does not use the GPU for final rendering. Only specific third-party effects use OpenGL and AE's own Raytrace 3D uses CUDA. Otherwise it's CPU rendering al lthe way.
ok ok. if i have nvidia gpu and have CUDA like GTX 970. it can be used for final rendering ?
media encoder support openGL ?
if i have nvidia gpu and have CUDA like GTX 970. it can be used for final rendering ?
No. The only thing AE really uses the GPU for during final rendering is the obsolete ray-traced renderer. Now, some third-party plugins like Element 3d will use the GPU, but they don't need it to be an NVIDIA card. You'll have to check their requirements.
Here's more info on the GPU in AE: GPU (CUDA, OpenGL) features in After Effects
And the obsolescence of the ray-traced renderer: http://motionworks.net/after-effects-3d-future/
Keep in mind that Premiere Pro DOES use the GPU.