Goblet

YOUR COMPUTER NOV. 83 - Page 205



GOBLET

Philip Jones, Abingdon, Oxfordshire



This program is designed to take a halfcross-section of an object and rotate it about the y-axis in eight stages thereby giving the picture of the object in a 3-D wire frame drawing. The 3-D picture is then rotated through 7.5 degrees and redrawn five times. Each time the picture is Saved in memory by a short machine-code program. When the drawing is complete, these pictures are called back in rapid succession to give the effect of the object spinning at about 20 rpm.



To create an object, enter the x and y co-ordinates of the points joined together in order - up tp a maximum of 16 - and then a number bigger than 256 to start the rest of the program. For example, to draw a goblet enter: 0, 0, 40, 0, 35, 10, 10, 15, 10, 60, 50, 65, 60, 100, 55, 100, 45, 70, 0, 64, 555. Make sure the co-ordiantes are such that the third dimension will not try and draw a line off the screen. It is best to start and finish with the y variable equal to zero. When you have finished drawing, enter 555 as an x co-ordinate.



The high-speed spinning can only be achieved on a 48K Spectrum because of the vast amount of memory taken in Saving the screen - nearly 37K - but wire frame pictures are possible on a 16K by deleting lines 1 to 130, line 600, line 603, line 850, lines 1000 to 1050 and changing 990 to 990 Go To 602.







cc 2020, Ignacio Prini Garcia (Spain)

Program typed and saved to .tap with Spectaculator 8.0