Actual source code: xtone.c


  2: /*
  3:     Code for drawing color interpolated triangles using X-windows.
  4: */
  5: #include <../src/sys/classes/draw/impls/x/ximpl.h>

  7: PETSC_INTERN PetscErrorCode PetscDrawInterpolatedTriangle_X(PetscDraw_X *, int, int, int, int, int, int, int, int, int);

  9: #define SHIFT_VAL 6

 11: PetscErrorCode PetscDrawInterpolatedTriangle_X(PetscDraw_X *win, int x1, int y_1, int t1, int x2, int y2, int t2, int x3, int y3, int t3)
 12: {
 13:   PetscReal rfrac, lfrac;
 14:   PetscReal R_y2_y_1, R_y3_y_1, R_y3_y2;
 15:   int       lc, rc = 0, lx, rx = 0, xx, y, c;
 16:   int       rc_lc, rx_lx, t2_t1, x2_x1, t3_t1, x3_x1, t3_t2, x3_x2;

 18:   PetscFunctionBegin;
 19:   /*
 20:         Is triangle even visible in window?
 21:   */
 22:   if (x1 < 0 && x2 < 0 && x3 < 0) PetscFunctionReturn(PETSC_SUCCESS);
 23:   if (y_1 < 0 && y2 < 0 && y3 < 0) PetscFunctionReturn(PETSC_SUCCESS);
 24:   if (x1 > win->w && x2 > win->w && x3 > win->w) PetscFunctionReturn(PETSC_SUCCESS);
 25:   if (y_1 > win->h && y2 > win->h && y3 > win->h) PetscFunctionReturn(PETSC_SUCCESS);

 27:   t1 = t1 << SHIFT_VAL;
 28:   t2 = t2 << SHIFT_VAL;
 29:   t3 = t3 << SHIFT_VAL;

 31:   /* Sort the vertices */
 32: #define SWAP(a, b) \
 33:   { \
 34:     int _a; \
 35:     _a = a; \
 36:     a  = b; \
 37:     b  = _a; \
 38:   }
 39:   if (y_1 > y2) {
 40:     SWAP(y_1, y2);
 41:     SWAP(t1, t2);
 42:     SWAP(x1, x2);
 43:   }
 44:   if (y_1 > y3) {
 45:     SWAP(y_1, y3);
 46:     SWAP(t1, t3);
 47:     SWAP(x1, x3);
 48:   }
 49:   if (y2 > y3) {
 50:     SWAP(y2, y3);
 51:     SWAP(t2, t3);
 52:     SWAP(x2, x3);
 53:   }
 54:   /* This code is decidedly non-optimal; it is intended to be a start at
 55:    an implementation */

 57:   if (y2 != y_1) R_y2_y_1 = 1.0 / ((double)(y2 - y_1));
 58:   else R_y2_y_1 = 0.0;
 59:   if (y3 != y_1) R_y3_y_1 = 1.0 / ((double)(y3 - y_1));
 60:   else R_y3_y_1 = 0.0;
 61:   t2_t1 = t2 - t1;
 62:   x2_x1 = x2 - x1;
 63:   t3_t1 = t3 - t1;
 64:   x3_x1 = x3 - x1;
 65:   for (y = y_1; y <= y2; y++) {
 66:     /* PetscDraw a line with the correct color from t1-t2 to t1-t3 */
 67:     /* Left color is (y-y_1)/(y2-y_1) * (t2-t1) + t1 */
 68:     lfrac = ((double)(y - y_1)) * R_y2_y_1;
 69:     lc    = (int)(lfrac * (t2_t1) + t1);
 70:     lx    = (int)(lfrac * (x2_x1) + x1);
 71:     /* Right color is (y-y_1)/(y3-y_1) * (t3-t1) + t1 */
 72:     rfrac = ((double)(y - y_1)) * R_y3_y_1;
 73:     rc    = (int)(rfrac * (t3_t1) + t1);
 74:     rx    = (int)(rfrac * (x3_x1) + x1);
 75:     /* PetscDraw the line */
 76:     rc_lc = rc - lc;
 77:     rx_lx = rx - lx;
 78:     if (rx > lx) {
 79:       for (xx = lx; xx <= rx; xx++) {
 80:         c = (((xx - lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
 81:         PetscDrawXiSetColor(win, c);
 82:         XDrawPoint(win->disp, PetscDrawXiDrawable(win), win->gc.set, xx, y);
 83:       }
 84:     } else if (rx < lx) {
 85:       for (xx = lx; xx >= rx; xx--) {
 86:         c = (((xx - lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
 87:         PetscDrawXiSetColor(win, c);
 88:         XDrawPoint(win->disp, PetscDrawXiDrawable(win), win->gc.set, xx, y);
 89:       }
 90:     } else {
 91:       c = lc >> SHIFT_VAL;
 92:       PetscDrawXiSetColor(win, c);
 93:       XDrawPoint(win->disp, PetscDrawXiDrawable(win), win->gc.set, lx, y);
 94:     }
 95:   }

 97:   /* For simplicity,"move" t1 to the intersection of t1-t3 with the line y=y2.
 98:      We take advantage of the previous iteration. */
 99:   if (y2 >= y3) PetscFunctionReturn(PETSC_SUCCESS);
100:   if (y_1 < y2) {
101:     t1  = rc;
102:     y_1 = y2;
103:     x1  = rx;

105:     t3_t1 = t3 - t1;
106:     x3_x1 = x3 - x1;
107:   }
108:   t3_t2 = t3 - t2;
109:   x3_x2 = x3 - x2;
110:   if (y3 != y2) R_y3_y2 = 1.0 / ((double)(y3 - y2));
111:   else R_y3_y2 = 0.0;
112:   if (y3 != y_1) R_y3_y_1 = 1.0 / ((double)(y3 - y_1));
113:   else R_y3_y_1 = 0.0;

115:   for (y = y2; y <= y3; y++) {
116:     /* PetscDraw a line with the correct color from t2-t3 to t1-t3 */
117:     /* Left color is (y-y_1)/(y2-y_1) * (t2-t1) + t1 */
118:     lfrac = ((double)(y - y2)) * R_y3_y2;
119:     lc    = (int)(lfrac * (t3_t2) + t2);
120:     lx    = (int)(lfrac * (x3_x2) + x2);
121:     /* Right color is (y-y_1)/(y3-y_1) * (t3-t1) + t1 */
122:     rfrac = ((double)(y - y_1)) * R_y3_y_1;
123:     rc    = (int)(rfrac * (t3_t1) + t1);
124:     rx    = (int)(rfrac * (x3_x1) + x1);
125:     /* PetscDraw the line */
126:     rc_lc = rc - lc;
127:     rx_lx = rx - lx;
128:     if (rx > lx) {
129:       for (xx = lx; xx <= rx; xx++) {
130:         c = (((xx - lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
131:         PetscDrawXiSetColor(win, c);
132:         XDrawPoint(win->disp, PetscDrawXiDrawable(win), win->gc.set, xx, y);
133:       }
134:     } else if (rx < lx) {
135:       for (xx = lx; xx >= rx; xx--) {
136:         c = (((xx - lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
137:         PetscDrawXiSetColor(win, c);
138:         XDrawPoint(win->disp, PetscDrawXiDrawable(win), win->gc.set, xx, y);
139:       }
140:     } else {
141:       c = lc >> SHIFT_VAL;
142:       PetscDrawXiSetColor(win, c);
143:       XDrawPoint(win->disp, PetscDrawXiDrawable(win), win->gc.set, lx, y);
144:     }
145:   }
146:   PetscFunctionReturn(PETSC_SUCCESS);
147: }