Which modeling technique is primarily used to create complex organic shapes by manipulating vertices?

The technique primarily used to create complex organic shapes by manipulating vertices is often recognized as mesh sculpting. This approach allows artists and designers to push, pull, and manipulate the surface of a mesh in a highly intuitive manner, making it ideal for organic shapes that require a high degree of detail and expressiveness.

In the context of modeling techniques, mesh sculpting involves working directly with a mesh's vertices, edges, and faces, providing immediate visual feedback as the model is reshaped. This method aligns closely with how sculptors work with physical materials, fostering creativity and facilitating the detailing of organic forms.

While other modeling techniques like polygon modeling, T-Spline modeling, and NURBS modeling have their own advantages and use cases, they do not focus primarily on the direct manipulation of vertices to achieve the level of complexity needed for organic shapes. Polygon modeling is more structured and relies heavily on polygons, T-Spline modeling combines some aspects of both polygonal and NURBS modeling with a focus on smooth surfaces, and NURBS modeling defines shapes mathematically with curves rather than direct vertex manipulation. Thus, mesh sculpting stands out as the most relevant method for creating complex organic shapes.