What are free tools for texture opacity 3D models?

Free tools for adjusting texture opacity in 3D models include Blender (full 3D software), GIMP, and Krita (image editors). Blender lets you tweak opacity directly in its shader editor—use alpha channels or mix nodes with the Principled BSDF shader. GIMP and Krita edit texture files’ alpha layers (which control opacity) before applying them to models. Beginners can start with Blender’s "Alpha" slider or GIMP’s layer opacity tool—both have free online guides to get going quickly.