Actual source code: tone.c

  1: /*$Id: tone.c,v 1.36 2001/03/23 23:20:15 balay Exp $*/

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

  8: #define SHIFT_VAL 6

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

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

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

 32:   /* Sort the vertices */
 33: #define SWAP(a,b) {int _a; _a=a; a=b; b=_a;}
 34:   if (y_1 > y2) {
 35:     SWAP(y_1,y2);SWAP(t1,t2); SWAP(x1,x2);
 36:   }
 37:   if (y_1 > y3) {
 38:     SWAP(y_1,y3);SWAP(t1,t3); SWAP(x1,x3);
 39:   }
 40:   if (y2 > y3) {
 41:     SWAP(y2,y3);SWAP(t2,t3); SWAP(x2,x3);
 42:   }
 43:   /* This code is decidely non-optimal; it is intended to be a start at
 44:    an implementation */

 46:   if (y2 != y_1) R_y2_y_1 = 1.0/((double)(y2-y_1)); else R_y2_y_1 = 0.0;
 47:   if (y3 != y_1) R_y3_y_1 = 1.0/((double)(y3-y_1)); else R_y3_y_1 = 0.0;
 48:   t2_t1   = t2 - t1;
 49:   x2_x1   = x2 - x1;
 50:   t3_t1   = t3 - t1;
 51:   x3_x1   = x3 - x1;
 52:   for (y=y_1; y<=y2; y++) {
 53:     /* PetscDraw a line with the correct color from t1-t2 to t1-t3 */
 54:     /* Left color is (y-y_1)/(y2-y_1) * (t2-t1) + t1 */
 55:     lfrac = ((double)(y-y_1)) * R_y2_y_1;
 56:     lc    = (int)(lfrac * (t2_t1) + t1);
 57:     lx    = (int)(lfrac * (x2_x1) + x1);
 58:     /* Right color is (y-y_1)/(y3-y_1) * (t3-t1) + t1 */
 59:     rfrac = ((double)(y - y_1)) * R_y3_y_1;
 60:     rc    = (int)(rfrac * (t3_t1) + t1);
 61:     rx    = (int)(rfrac * (x3_x1) + x1);
 62:     /* PetscDraw the line */
 63:     rc_lc = rc - lc;
 64:     rx_lx = rx - lx;
 65:     if (rx > lx) {
 66:       for (xx=lx; xx<=rx; xx++) {
 67:         c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
 68:         XiSetColor(win,c);
 69:         XDrawPoint(win->disp,XiDrawable(win),win->gc.set,xx,y);
 70:       }
 71:     } else if (rx < lx) {
 72:       for (xx=lx; xx>=rx; xx--) {
 73:         c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
 74:         XiSetColor(win,c);
 75:         XDrawPoint(win->disp,XiDrawable(win),win->gc.set,xx,y);
 76:       }
 77:     } else {
 78:       c = lc >> SHIFT_VAL;
 79:       XiSetColor(win,c);
 80:       XDrawPoint(win->disp,XiDrawable(win),win->gc.set,lx,y);
 81:     }
 82:   }

 84:   /* For simplicity,"move" t1 to the intersection of t1-t3 with the line y=y2.
 85:      We take advantage of the previous iteration. */
 86:   if (y2 >= y3) return(0);
 87:   if (y_1 < y2) {
 88:     t1  = rc;
 89:     y_1 = y2;
 90:     x1  = rx;

 92:     t3_t1   = t3 - t1;
 93:     x3_x1   = x3 - x1;
 94:   }
 95:   t3_t2 = t3 - t2;
 96:   x3_x2 = x3 - x2;
 97:   if (y3 != y2) R_y3_y2 = 1.0/((double)(y3-y2)); else R_y3_y2 = 0.0;
 98:   if (y3 != y_1) R_y3_y_1 = 1.0/((double)(y3-y_1)); else R_y3_y_1 = 0.0;
 99:   for (y=y2; y<=y3; y++) {
100:     /* PetscDraw a line with the correct color from t2-t3 to t1-t3 */
101:     /* Left color is (y-y_1)/(y2-y_1) * (t2-t1) + t1 */
102:     lfrac = ((double)(y-y2)) * R_y3_y2;
103:     lc    = (int)(lfrac * (t3_t2) + t2);
104:     lx    = (int)(lfrac * (x3_x2) + x2);
105:     /* Right color is (y-y_1)/(y3-y_1) * (t3-t1) + t1 */
106:     rfrac = ((double)(y - y_1)) * R_y3_y_1;
107:     rc    = (int)(rfrac * (t3_t1) + t1);
108:     rx    = (int)(rfrac * (x3_x1) + x1);
109:     /* PetscDraw the line */
110:     rc_lc = rc - lc;
111:     rx_lx = rx - lx;
112:     if (rx > lx) {
113:       for (xx=lx; xx<=rx; xx++) {
114:         c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
115:         XiSetColor(win,c);
116:         XDrawPoint(win->disp,XiDrawable(win),win->gc.set,xx,y);
117:       }
118:     } else if (rx < lx) {
119:       for (xx=lx; xx>=rx; xx--) {
120:         c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
121:         XiSetColor(win,c);
122:         XDrawPoint(win->disp,XiDrawable(win),win->gc.set,xx,y);
123:       }
124:     } else {
125:       c = lc >> SHIFT_VAL;
126:       XiSetColor(win,c);
127:       XDrawPoint(win->disp,XiDrawable(win),win->gc.set,lx,y);
128:     }
129:   }
130:   return(0);
131: }