162 lines
7.6 KiB
Markdown
162 lines
7.6 KiB
Markdown
**LISTING 51.1 L51-1.C**
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/* 3D animation program to view a cube as it rotates in Mode X. The viewpoint
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is fixed at the origin (0,0,0) of world space, looking in the direction of
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increasingly negative Z. A right-handed coordinate system is used throughout.
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All C code tested with Borland C++ in C compilation mode. */
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#include <conio.h>
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#include <dos.h>
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#include <math.h>
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#include "polygon.h"
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#define ROTATION (M_PI / 30.0) /* rotate by 6 degrees at a time */
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/* base offset of page to which to draw */
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unsigned int CurrentPageBase = 0;
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/* Clip rectangle; clips to the screen */
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int ClipMinX=0, ClipMinY=0;
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int ClipMaxX=SCREEN_WIDTH, ClipMaxY=SCREEN_HEIGHT;
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/* Rectangle specifying extent to be erased in each page. */
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struct Rect EraseRect[2] = { {0, 0, SCREEN_WIDTH, SCREEN_HEIGHT},
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{0, 0, SCREEN_WIDTH, SCREEN_HEIGHT} };
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static unsigned int PageStartOffsets[2] =
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{PAGE0_START_OFFSET,PAGE1_START_OFFSET};
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int DisplayedPage, NonDisplayedPage;
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/* Transformation from cube's object space to world space. Initially
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set up to perform no rotation and to move the cube into world
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space -100 units away from the origin down the Z axis. Given the
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viewing point, -100 down the Z axis means 100 units away in the
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direction of view. The program dynamically changes both the
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translation and the rotation. */
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static double CubeWorldXform[4][4] = {
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{1.0, 0.0, 0.0, 0.0},
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{0.0, 1.0, 0.0, 0.0},
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{0.0, 0.0, 1.0, -100.0},
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{0.0, 0.0, 0.0, 1.0} };
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/* Transformation from world space into view space. Because in this
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application the view point is fixed at the origin of world space,
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looking down the Z axis in the direction of increasing Z, view space is
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identical to world space, and this is the identity matrix. */
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static double WorldViewXform[4][4] = {
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{1.0, 0.0, 0.0, 0.0},
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{0.0, 1.0, 0.0, 0.0},
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{0.0, 0.0, 1.0, 0.0},
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{0.0, 0.0, 0.0, 1.0}
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};
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/* all vertices in the cube */
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static struct Point3 CubeVerts[] = {
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{15,15,15,1},{15,15,-15,1},{15,-15,15,1},{15,-15,-15,1},
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{-15,15,15,1},{-15,15,-15,1},{-15,-15,15,1},{-15,-15,-15,1}};
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/* vertices after transformation */
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static struct Point3
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XformedCubeVerts[sizeof(CubeVerts)/sizeof(struct Point3)];
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/* vertices after projection */
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static struct Point3
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ProjectedCubeVerts[sizeof(CubeVerts)/sizeof(struct Point3)];
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/* vertices in screen coordinates */
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static struct Point
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ScreenCubeVerts[sizeof(CubeVerts)/sizeof(struct Point3)];
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/* vertex indices for individual faces */
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static int Face1[] = {1,3,2,0};
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static int Face2[] = {5,7,3,1};
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static int Face3[] = {4,5,1,0};
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static int Face4[] = {3,7,6,2};
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static int Face5[] = {5,4,6,7};
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static int Face6[] = {0,2,6,4};
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/* list of cube faces */
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static struct Face CubeFaces[] = {{Face1,4,15},{Face2,4,14},
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{Face3,4,12},{Face4,4,11},{Face5,4,10},{Face6,4,9}};
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/* master description for cube */
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static struct Object Cube = {sizeof(CubeVerts)/sizeof(struct Point3),
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CubeVerts, XformedCubeVerts, ProjectedCubeVerts, ScreenCubeVerts,
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sizeof(CubeFaces)/sizeof(struct Face), CubeFaces};
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void main() {
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int Done = 0, RecalcXform = 1;
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double WorkingXform[4][4];
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union REGS regset;
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/* Set up the initial transformation */
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Set320x240Mode(); /* set the screen to Mode X */
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ShowPage(PageStartOffsets[DisplayedPage = 0]);
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/* Keep transforming the cube, drawing it to the undisplayed page,
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and flipping the page to show it */
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do {
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/* Regenerate the object->view transformation and
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retransform/project if necessary */
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if (RecalcXform) {
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ConcatXforms(WorldViewXform, CubeWorldXform, WorkingXform);
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/* Transform and project all the vertices in the cube */
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XformAndProjectPoints(WorkingXform, &Cube);
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RecalcXform = 0;
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}
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CurrentPageBase = /* select other page for drawing to */
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PageStartOffsets[NonDisplayedPage = DisplayedPage ^ 1];
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/* Clear the portion of the non-displayed page that was drawn
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to last time, then reset the erase extent */
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FillRectangleX(EraseRect[NonDisplayedPage].Left,
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EraseRect[NonDisplayedPage].Top,
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EraseRect[NonDisplayedPage].Right,
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EraseRect[NonDisplayedPage].Bottom, CurrentPageBase, 0);
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EraseRect[NonDisplayedPage].Left =
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EraseRect[NonDisplayedPage].Top = 0x7FFF;
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EraseRect[NonDisplayedPage].Right =
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EraseRect[NonDisplayedPage].Bottom = 0;
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/* Draw all visible faces of the cube */
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DrawVisibleFaces(&Cube);
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/* Flip to display the page into which we just drew */
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ShowPage(PageStartOffsets[DisplayedPage = NonDisplayedPage]);
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while (kbhit()) {
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switch (getch()) {
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case 0x1B: /* Esc to exit */
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Done = 1; break;
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case ‘A': case ‘a': /* away (-Z) */
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CubeWorldXform[2][3] -= 3.0; RecalcXform = 1; break;
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case ‘T': /* towards (+Z). Don't allow to get too */
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case ‘t': /* close, so Z clipping isn't needed */
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if (CubeWorldXform[2][3] < -40.0) {
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CubeWorldXform[2][3] += 3.0;
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RecalcXform = 1;
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}
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break;
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case ‘4': /* rotate clockwise around Y */
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AppendRotationY(CubeWorldXform, -ROTATION);
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RecalcXform=1; break;
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case ‘6': /* rotate counterclockwise around Y */
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AppendRotationY(CubeWorldXform, ROTATION);
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RecalcXform=1; break;
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case ‘8': /* rotate clockwise around X */
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AppendRotationX(CubeWorldXform, -ROTATION);
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RecalcXform=1; break;
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case ‘2': /* rotate counterclockwise around X */
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AppendRotationX(CubeWorldXform, ROTATION);
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RecalcXform=1; break;
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case 0: /* extended code */
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switch (getch()) {
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case 0x3B: /* rotate counterclockwise around Z */
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AppendRotationZ(CubeWorldXform, ROTATION);
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RecalcXform=1; break;
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case 0x3C: /* rotate clockwise around Z */
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AppendRotationZ(CubeWorldXform, -ROTATION);
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RecalcXform=1; break;
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case 0x4B: /* left (-X) */
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CubeWorldXform[0][3] -= 3.0; RecalcXform=1; break;
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case 0x4D: /* right (+X) */
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CubeWorldXform[0][3] += 3.0; RecalcXform=1; break;
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case 0x48: /* up (+Y) */
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CubeWorldXform[1][3] += 3.0; RecalcXform=1; break;
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case 0x50: /* down (-Y) */
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CubeWorldXform[1][3] -= 3.0; RecalcXform=1; break;
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default:
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break;
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}
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break;
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default: /* any other key to pause */
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getch(); break;
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}
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}
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} while (!Done);
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/* Return to text mode and exit */
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regset.x.ax = 0x0003; /* AL = 3 selects 80x25 text mode */
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int86(0x10, ®set, ®set);
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}
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