1 2 /* 3 Code for drawing color interpolated triangles using X-windows. 4 */ 5 #include <../src/sys/classes/draw/impls/x/ximpl.h> 6 7 PETSC_INTERN PetscErrorCode PetscDrawInterpolatedTriangle_X(PetscDraw_X*,int,int,int,int,int,int,int,int,int); 8 9 #define SHIFT_VAL 6 10 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; 17 18 PetscFunctionBegin; 19 /* 20 Is triangle even visible in window? 21 */ 22 if (x1 < 0 && x2 < 0 && x3 < 0) PetscFunctionReturn(0); 23 if (y_1 < 0 && y2 < 0 && y3 < 0) PetscFunctionReturn(0); 24 if (x1 > win->w && x2 > win->w && x3 > win->w) PetscFunctionReturn(0); 25 if (y_1 > win->h && y2 > win->h && y3 > win->h) PetscFunctionReturn(0); 26 27 t1 = t1 << SHIFT_VAL; 28 t2 = t2 << SHIFT_VAL; 29 t3 = t3 << SHIFT_VAL; 30 31 /* Sort the vertices */ 32 #define SWAP(a,b) {int _a; _a=a; a=b; b=_a;} 33 if (y_1 > y2) { 34 SWAP(y_1,y2);SWAP(t1,t2); SWAP(x1,x2); 35 } 36 if (y_1 > y3) { 37 SWAP(y_1,y3);SWAP(t1,t3); SWAP(x1,x3); 38 } 39 if (y2 > y3) { 40 SWAP(y2,y3);SWAP(t2,t3); SWAP(x2,x3); 41 } 42 /* This code is decidely non-optimal; it is intended to be a start at 43 an implementation */ 44 45 if (y2 != y_1) R_y2_y_1 = 1.0/((double)(y2-y_1)); 46 else R_y2_y_1 = 0.0; 47 if (y3 != y_1) R_y3_y_1 = 1.0/((double)(y3-y_1)); 48 else R_y3_y_1 = 0.0; 49 t2_t1 = t2 - t1; 50 x2_x1 = x2 - x1; 51 t3_t1 = t3 - t1; 52 x3_x1 = x3 - x1; 53 for (y=y_1; y<=y2; y++) { 54 /* PetscDraw a line with the correct color from t1-t2 to t1-t3 */ 55 /* Left color is (y-y_1)/(y2-y_1) * (t2-t1) + t1 */ 56 lfrac = ((double)(y-y_1)) * R_y2_y_1; 57 lc = (int)(lfrac * (t2_t1) + t1); 58 lx = (int)(lfrac * (x2_x1) + x1); 59 /* Right color is (y-y_1)/(y3-y_1) * (t3-t1) + t1 */ 60 rfrac = ((double)(y - y_1)) * R_y3_y_1; 61 rc = (int)(rfrac * (t3_t1) + t1); 62 rx = (int)(rfrac * (x3_x1) + x1); 63 /* PetscDraw the line */ 64 rc_lc = rc - lc; 65 rx_lx = rx - lx; 66 if (rx > lx) { 67 for (xx=lx; xx<=rx; xx++) { 68 c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL; 69 PetscDrawXiSetColor(win,c); 70 XDrawPoint(win->disp,PetscDrawXiDrawable(win),win->gc.set,xx,y); 71 } 72 } else if (rx < lx) { 73 for (xx=lx; xx>=rx; xx--) { 74 c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL; 75 PetscDrawXiSetColor(win,c); 76 XDrawPoint(win->disp,PetscDrawXiDrawable(win),win->gc.set,xx,y); 77 } 78 } else { 79 c = lc >> SHIFT_VAL; 80 PetscDrawXiSetColor(win,c); 81 XDrawPoint(win->disp,PetscDrawXiDrawable(win),win->gc.set,lx,y); 82 } 83 } 84 85 /* For simplicity,"move" t1 to the intersection of t1-t3 with the line y=y2. 86 We take advantage of the previous iteration. */ 87 if (y2 >= y3) PetscFunctionReturn(0); 88 if (y_1 < y2) { 89 t1 = rc; 90 y_1 = y2; 91 x1 = rx; 92 93 t3_t1 = t3 - t1; 94 x3_x1 = x3 - x1; 95 } 96 t3_t2 = t3 - t2; 97 x3_x2 = x3 - x2; 98 if (y3 != y2) R_y3_y2 = 1.0/((double)(y3-y2)); 99 else R_y3_y2 = 0.0; 100 if (y3 != y_1) R_y3_y_1 = 1.0/((double)(y3-y_1)); 101 else R_y3_y_1 = 0.0; 102 103 for (y=y2; y<=y3; y++) { 104 /* PetscDraw a line with the correct color from t2-t3 to t1-t3 */ 105 /* Left color is (y-y_1)/(y2-y_1) * (t2-t1) + t1 */ 106 lfrac = ((double)(y-y2)) * R_y3_y2; 107 lc = (int)(lfrac * (t3_t2) + t2); 108 lx = (int)(lfrac * (x3_x2) + x2); 109 /* Right color is (y-y_1)/(y3-y_1) * (t3-t1) + t1 */ 110 rfrac = ((double)(y - y_1)) * R_y3_y_1; 111 rc = (int)(rfrac * (t3_t1) + t1); 112 rx = (int)(rfrac * (x3_x1) + x1); 113 /* PetscDraw the line */ 114 rc_lc = rc - lc; 115 rx_lx = rx - lx; 116 if (rx > lx) { 117 for (xx=lx; xx<=rx; xx++) { 118 c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL; 119 PetscDrawXiSetColor(win,c); 120 XDrawPoint(win->disp,PetscDrawXiDrawable(win),win->gc.set,xx,y); 121 } 122 } else if (rx < lx) { 123 for (xx=lx; xx>=rx; xx--) { 124 c = (((xx-lx) * (rc_lc)) / (rx_lx) + lc) >> SHIFT_VAL; 125 PetscDrawXiSetColor(win,c); 126 XDrawPoint(win->disp,PetscDrawXiDrawable(win),win->gc.set,xx,y); 127 } 128 } else { 129 c = lc >> SHIFT_VAL; 130 PetscDrawXiSetColor(win,c); 131 XDrawPoint(win->disp,PetscDrawXiDrawable(win),win->gc.set,lx,y); 132 } 133 } 134 PetscFunctionReturn(0); 135 } 136