I want just my dice to be blur. Is it possible only my dice to be blur and have the rest of the scene to be as it is. I have searched for the video and tried in node tree defocus but fail to get the effect. What is lacking in my node so that i can just blur the dice. Any suggestion or help . Thanks
You can do compositing to selective parts of a scene by using render layers. In your case you need two render layers. The first one should contain your everything except the dice. The second one should contain your dice and have "sky" disabled. The red cube is in the normal render layer and the blue cube is in the blur render layer. Here is an example compositor setup to get the effect you want.