Suppose you are planning to buy a new furniture for your room! Before finalizing anything, you can first start by snapping a picture of your room then place the furniture and visualize that design in 3D.
HomeStyler for Android is a free application which enables you to visualize your ideas before finalizing them on a design.
After you capture a photograph, HomeStyler intelligently identifies its visible corners and provides you features for aligning the walls with your room corners then adjust all measurements so that you can test new things as per your room size.
There are many other options like you can virtually test paint color on your walls, you can virtually see sofa set, bed or any other furniture (which you are planning to buy) placed in your room. You can also virtually experiment lighting style, paintings, doors and windows etc.