When buying a condo in a project that is little more than an idea on paper, a hole in the ground, or a stubby concrete shell -- it takes some imagination to put real money down. These days, this is the major challenge facing many of the downtown Austin condo sales centers as they try to sell units to prospective buyers.To solve this problem, the Four Seasons Residences has created an unusually over-the-top video rendering of ttheir future building. Since thd buidling is little more than a 20 foot tall concrete shell supported by wood planks, the video . . .