There are several Free/Libre and Open Source Software packages(F/LOSS) to use in creating Hollywood caliber and professional level computer graphics. Most are multi-platform.

Krita - raster graphics editor for KDE
GIMP - photo manipulation
Inkscape - vector graphics editor
Natron - compositor inspired by Nuke
Handbrake - video transcoder
VLC - media player and streamer
FFMPEG - video recorder and transcoder
OpenToonz - OS version of Studio Ghibli's Toonz
MyPaint - raster graphics editor
SynFig - vector 2D animation
Pencil2D - animation and drawing
OpenShot - video editor
Lux Render - a physically based and unbiased rendering engine for Blender and many other 3D packages