3-D Wire Frame Graphics

The program listed below allows a person to define a 3-D object, draw it on the screen, and rotate it in three different planes.

The heart of the program lies in how the object is represented. Two arrays hold the information for the object. An vertex array (list) holds all of the vertices. An edge array (list) holds the two endpoints of the edges. The edgel array refers back to the vertex list for the actual points. It only holds the number of the vertex.

Lines 100 to 1030 in the program holds the definition of a cube and some values for variables used by the program. Look at the diagrams and the the two lists to see how the cube is defined. More complex figures will take more information.

The center of the cube is (0,0,90). This can be changed by the user. The variables XX, YY, and ZZ define the center that the user chooses.

There are four procedures in the program. They are treated as keywords. To display the object the user can type in directly, or in a progran, DISPLAYS3D, ROTX, ROTY, and ROTZ rotate the object in radians held by the variable ROT. The program says that ROT is 20, its wrong. It should be in radians, like PI/10. Just to refresh your memory PI/2 is 90 degrees.

When a rotation procedure is called the object is spun in the axis defined. Since the Z axis is pointing out of the screen, rotating the object will make it appear to spin like it is ona turntable and you are looking down on it. I hope this is clear.

The variable D2 changes how large the object is on the screen. The larger the number the smaller the object.

When you run the program as it is, nothing appears to happen. All it has done is to load the array with the data and set up the variables. Type ROTX, ROTY, and then DISPLAY3D. You will now see the cube at an angle.

Have fun with the progran. If you have any questions feel free to contact me. Its hard to Summarize a lot of material ina short article.

100 DiM vertex (100, 3) 
110 DIM edge (200,2) 
190 RESTORE 
200 READ xcenter, ycenter 
210 READ d1, d2, rot 
220 READ xx, yy, zz 
230 READ vertexcount 
240 FOR loop = 1 TO vertexcount 
250 FOR loop2 = 1 TO 3 
260 READ vertex (loop, loop2) 
270 NEXT 1oop2 
280 NEXT loop 
290 READ edgecount 
300 FOR loop = 1 TO edgecount 
310 READ edge (loop, 1) 
320 READ edge (loop, 2) 
330 NEXT 1oop 
1000 DATA 40,40, 1, 10,20 
1010 DATA 9,0,0 
1020 DATA 8,-1,-1,1,-1,1,1,1,-1,1,1,1,1,1,1, -1,1,-1,-1,-1,-1,-1,-1,1,-1
1030 DATA 12,1,2,2,4,4,3,3,1,7,8,
8,5,5,5,6,7,7,1,5,3,5,4,8,2 
9000 DEFine PROCedure rotz 
9010 FOR loop = 1 TO vertexcount 
9020 x1 = vertex(lcop, 1) *COS (roti-vertex (loop, 2) *SIN (rot) 
9030 71 = vertex(loop, 1)*SIN (rot. tvertex (loop, 2) *cos (rot) 
9040 vertex (loop, 1) = x1 
9050 vertex (loop, 2) = y1 
9060 NEXT 100p 
9090 END DEFine rotz 
9100 DEFine PPOCedure roty 
9110 FOR logp = 1 TO vertexcount* 
9120 x1 = vertex (lcop, 1) *COS (rot)-vertex (loop, 3) *SIN (rot) 
9130 z1 = vertex(loop, 1) *SIN (rot) +vertex (loop, 3) *COS (rot) 
9140 vertex (loop, 1) = x1 
9150 vertex (loop, 3) = z1 
9160 NEXT 1oop 
9190 END DEFine roty 
9200 DEFine PROCedure rotx 
9210 FOR 1oop = 1 TO vertexcount
9220 y1 = vertex (loop, 2) *COS (rot)-vertex (loop, 3) *SIN (rot) 
9230 z1 = vertex (loop,2) *SIN (rot) vertex (loop, 3) *COS (rot) 
9240 vertex (loop, 2) = y1 
9250 vertex (1oop,3) = z1
9260 NEXT loop 
9290 END DEFine rotx 
9300 DEFine FuNction transx (x, d1, d2) 
9305 LOCal xprime 
9310 xprime = (x*d2)/d1 
9315 RETurn xprime 
9320 END DEFine transx 
9330 DEFine FuNction transy (y, d1, d2) 
9335 LOCal yprime 
9340 yprime = (y*d2)/d1 9345 RETurn yprime 
9350 END DEFine transy 
9400 DEFine PROCedure display3d 
9405 CLS 
9410 FOR loop = 1 TO edgecount 
9420 LET point1 = edge (loop, 1) 
9430 LET point = edge (loop, 2) 
9435 LET x1 = vertex(point1,1) - xX 
9440 LET ×1 = transx (x1, d1, d2) 
9445 LET ×2 = vertex (point2, 1) - xx 
9450 LET x2 = transx (x2, d1, d2) 
9455 LET y1 = verte(point1, 2) - УУ 
9460 LET y1 = transy (y1, d1, d2) 
9465 LET y2 = vertex (point2,2) - yy 
9470 LET y2 = transy (y2, d1, d2) 
9480 LINE x1+xcenter, y1+ycenter 10 x2+xcenter, y2+ycenter 
9490 NEXT loop 
9495 END DEFine display3d