What is the best 3D modeling program to create realistic objects?

First. there is no "best program" since whoever dominates the 3D art has its own preferred software. The software is just a tool and the artist always comes first. The software is only the brush, nothing more than that.

There are various software and each directed to any area of ​​computer graphics. For example, compare the Mudbox software 3Ds Max is a complete mistake, because they were made to work together, that is, you will always be working with a set of software, especially when it comes to 3D art for games. There is a whole process of creating and studies ladder.

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The creation process is basically the following:

1. modeling realistic 3D object (you choose for your preferred software and some of them has its limitations, but it all depends on what you're trying to do, and basically with Max and Mudbox 3ds you do anything in 3D, but could use Maya and ZBrush or only 3ds max or just Zbrush, it all depends!).
2. you do not model something super realistic without first modeling basic things, basic things you easily models in traditional 3D software like 3ds Max, Maya, Softimage, Cinema4d, Blender, Lightwave, Modo etc.
3. it requires an in-depth study and to model a character, for example, is extremely important to study anatomy and train your perception in 3D software.
4. each engine, and UDK or Cryengine itself, among others, has its own import plugins. 3ds Max communicates easily with both the UDK as with CryEngine, or you export a complete character with bones, textures etc. into the engine. But remember, nothing is so simple, it requires a treatment from the pupil of the eye to the fingernail. This level of demand we learn only after making numerous tests with the simplest things. There is no way to step higher than the leg in which case it would just learn to accelerate the car without knowing turn the wheel, slam on the brakes etc.