To mix displacement 3D models for rendering, use displacement maps or modifiers on a base mesh, then blend details via layer masking, weight painting, or shader node mixing (common in Blender, Maya, or Substance Painter).
This combines multiple depth elements (e.g., surface texture, mesh variations) without overcomplicating the base model. Key steps: Align UVs for consistent mapping, test blend strength to avoid artifacts, and preview in real-time.
For beginners, try Blender’s Shader Editor: Connect two displacement nodes to a MixRGB node, then use a grayscale texture to control where each displacement applies—start with subtle blends to practice.