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

 13: 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)
 14: {
 15:   PetscReal rfrac,lfrac;
 16:   PetscReal R_y2_y_1,R_y3_y_1,R_y3_y2;
 17:   int       lc,rc = 0,lx,rx = 0,xx,y,c;
 18:   int       rc_lc,rx_lx,t2_t1,x2_x1,t3_t1,x3_x1,t3_t2,x3_x2;

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

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

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

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

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

 95:     t3_t1 = t3 - t1;
 96:     x3_x1 = x3 - x1;
 97:   }
 98:   t3_t2 = t3 - t2;
 99:   x3_x2 = x3 - x2;
100:   if (y3 != y2) R_y3_y2 = 1.0/((double)(y3-y2));
101:   else R_y3_y2 = 0.0;
102:   if (y3 != y_1) R_y3_y_1 = 1.0/((double)(y3-y_1));
103:   else R_y3_y_1 = 0.0;

105:   for (y=y2; y<=y3; y++) {
106:     /* PetscDraw a line with the correct color from t2-t3 to t1-t3 */
107:     /* Left color is (y-y_1)/(y2-y_1) * (t2-t1) + t1 */
108:     lfrac = ((double)(y-y2)) * R_y3_y2;
109:     lc    = (int)(lfrac * (t3_t2) + t2);
110:     lx    = (int)(lfrac * (x3_x2) + x2);
111:     /* Right color is (y-y_1)/(y3-y_1) * (t3-t1) + t1 */
112:     rfrac = ((double)(y - y_1)) * R_y3_y_1;
113:     rc    = (int)(rfrac * (t3_t1) + t1);
114:     rx    = (int)(rfrac * (x3_x1) + x1);
115:     /* PetscDraw the line */
116:     rc_lc = rc - lc;
117:     rx_lx = rx - lx;
118:     if (rx > lx) {
119:       for (xx=lx; xx<=rx; xx++) {
120:         c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
121:         PetscDrawXiSetColor(win,c);
122:         XDrawPoint(win->disp,PetscDrawXiDrawable(win),win->gc.set,xx,y);
123:       }
124:     } else if (rx < lx) {
125:       for (xx=lx; xx>=rx; xx--) {
126:         c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL;
127:         PetscDrawXiSetColor(win,c);
128:         XDrawPoint(win->disp,PetscDrawXiDrawable(win),win->gc.set,xx,y);
129:       }
130:     } else {
131:       c = lc >> SHIFT_VAL;
132:       PetscDrawXiSetColor(win,c);
133:       XDrawPoint(win->disp,PetscDrawXiDrawable(win),win->gc.set,lx,y);
134:     }
135:   }
136:   return(0);
137: }