nicholl-lee-nicholl的标准实现

参照nicholl-lee-nicholl的原始论文而成,版权归nicholl-lee-nicholl所有.

void leftcolumn(float*, float*, float*, float*, float, float, float, float, bool*);void centercolumn(float*, float*, float*, float*, float, float, float, float, bool*);void topleftcorner(float*, float*, float*, float*, float, float, float, float, bool*);void inside(float*, float*, float*, float*, float, float, float, float, bool*);void p2topleft(float*, float*, float*, float*, float, float, float, float, bool*);void leftedge(float*, float*, float*, float*, float, float, float, float, bool*);void leftbottomregion(float*, float*, float*, float*, float, float, float, float, bool*, float, float, float);void p2bottom(float*, float*, float*, float*, float, float, float, float, bool*, float, float);void nlnclip(float* x1, float *y1, float *x2, float *y2, float left, float right, float bottom, float top, bool* visible){if (*x1 < left)leftcolumn(x1, y1, x2, y2, left, right, bottom, top, visible);else if (*x1 > right) {rotate180c(x1, y1); rotate180c(x2, y2);leftcolumn(x1, y1, x2, y2, -right, -left, -top, -bottom, visible);rotate180c(x1, y1); rotate180c(x2, y2);} elsecentercolumn(x1, y1, x2, y2, left, right, bottom, top, visible);}void leftcolumn(float* x1, float* y1, float* x2, float* y2, float left, float right, float bottom, float top, bool* visible){if (*x2 < left) *visible = false;else if (*y1 > top) topleftcorner(x1, y1, x2, y2, left, right, bottom, top, visible);else if (*y1 < bottom) {reflectxaxis(x1, y1); reflectxaxis(x2, y2);topleftcorner(x1, y1, x2, y2, left, right, -top, -bottom, visible);reflectxaxis(x1, y1); reflectxaxis(x2, y2);} else leftedge(x1, y1, x2, y2, left, right, bottom, top, visible);}void topleftcorner(float* x1, float* y1, float* x2, float* y2, float left, float right, float bottom, float top, bool* visible){float leftproduct, topproduct;float relx, rely;if (*y2 > top)*visible = false;else {relx = *x2 - *x1; rely = *y2 - *y1;leftproduct = (left - *x1) * rely;topproduct = (top - *y1) * relx;if (topproduct > leftproduct) leftbottomregion(x1, y1, x2, y2, left, right, bottom, top, visible, relx, rely, leftproduct);else {reflectxminusy(x1, y1); reflectxminusy(x2, y2);leftbottomregion(x1, y1, x2, y2, -top, -bottom, -right, -left, visible, -rely, -relx, topproduct);reflectxminusy(x1, y1); reflectxminusy(x2, y2);}}}void leftbottomregion(float* x1, float* y1, float* x2, float* y2, float left, float right, float bottom, float top, bool* visible, float relx, float rely, float leftproduct){float slope;float bottomproduct, rightproduct;if (*y2 > bottom) {slope = rely / relx;if (*x2 > right) {*y2 = (right - *x1) * slope + *y1;*x2 = right;} *y1 = (left - *x1) * slope + *y1;*x1 = left;*visible = true;} else {bottomproduct = (bottom - *y1) * relx;if (bottomproduct > leftproduct)*visible = false;else {rightproduct = (right - *x1) * rely;if (bottomproduct > rightproduct) {slope = rely / relx;*y1 = (left - *x1) * slope + *y1;*x1 = left;*x2 = (bottom - *y1) / slope + *x1;*y2 = bottom;*visible = true;} else {slope = rely / relx;*y1 = (left - *x1) * slope + *y1;*x1 = left;*y2 = (right - *x1) * slope + *y1;*x2 = right;*visible = true;}}}}void leftedge(float* x1, float* y1, float* x2, float* y2, float left, float right, float bottom, float top, bool* visible){float slope;float relx, rely;relx = *x2 - *x1; rely = *y2 - *y1;if (*x2 < left)*visible = false;else if (*y2 < bottom) p2bottom(x1, y1, x2, y2, left, right, bottom, top, visible, relx, rely);else if (*y2 > top) {reflectxaxis(x1, y1); reflectxaxis(x2, y2);p2bottom(x1, y1, x2, y2, left, right, -top, -bottom, visible, relx, -rely);reflectxaxis(x1, y1); reflectxaxis(x2, y2);} else {slope = rely / relx;if (*x2 > right) {*y2 = (right - *x1) * slope + *y1;*x2 = right;} *y1 = (left - *x1) * slope + *y1;*x1 = left;*visible = true;}}void p2bottom(float* x1, float* y1, float* x2, float* y2, float left, float right, float bottom, float top, bool* visible, float relx, float rely){float leftproduct, bottomproduct, rightproduct;float slope;leftproduct = (left - *x1) * rely;bottomproduct = (bottom - *y1) * relx;if (bottomproduct > leftproduct) *visible = false;else {rightproduct = (right - *x1) * rely;if (bottomproduct > rightproduct) {slope = rely / relx;*y1 = (left - *x1) * slope + *y1;*x1 = left;*x2 = (bottom - *y1) / slope + *x1;*y2 = bottom;*visible = true;} else {slope = rely / relx;*y1 = (left - *x1) * slope + *y1;*x1 = left;*y2 = (right - *x1) * slope + *y1;*x2 = right;*visible = true;}}}void centercolumn(float* x1, float* y1, float* x2, float* y2, float left, float right, float bottom, float top, bool* visible){if (*y1 > top) {rotate270c(x1, y1); rotate270c(x2, y2);leftedge(x1, y1, x2, y2, -top, -bottom, left, right, visible);rotate90c(x1, y1); rotate90c(x2, y2);} else if (*y1 < bottom) {rotate90c(x1, y1); rotate90c(x2, y2);leftedge(x1, y1, x2, y2, bottom, top, -right, -left, visible);rotate270c(x1, y1); rotate270c(x2, y2);} elseinside(x1, y1, x2, y2, left, right, bottom, top, visible);}void inside(float* x1, float* y1, float* x2, float* y2, float left, float right, float bottom, float top, bool* visible){float relx, rely;if (*x2 < left) {if (*y2 > top) p2topleft(x1, y1, x2, y2, left, right, bottom, top, visible);else if (*y2 < bottom) {reflectxaxis(x1, y1); reflectxaxis(x2, y2);p2topleft(x1, y1, x2, y2, left, right, -top, -bottom, visible);reflectxaxis(x1, y1); reflectxaxis(x2, y2);} else {relx = *x2 - *x1; rely = *y2 - *y1;*y2 = (left - *x1) * rely / relx + *y1;*x2 = left;*visible = true;}} else if (*x2 > right) {if (*y2 > top) {rotate270c(x1, y1); rotate270c(x2, y2);p2topleft(x1, y1, x2, y2, -top, -bottom, left, right, visible);rotate90c(x1, y1); rotate90c(x2, y2);} else if (*y2 < bottom) {rotate180c(x1, y1); rotate180c(x2, y2);p2topleft(x1, y1, x2, y2, -right, -left, -top, -bottom, visible);rotate180c(x1, y1); rotate180c(x2, y2);} else {relx = *x2 - *x1; rely = *y2 - *y1;*y2 = (right - *x1) * rely / relx + *y1;*x2 = right;*visible = true;}} else if (*y2 > top) {relx = *x2 - *x1; rely = *y2 - *y1;*x2 = (top - *y1) * relx / rely + *x1;*y2 = top;*visible = true;} else if (*y2 < bottom) {relx = *x2 - *x1; rely = *y2 - *y1;*x2 = (bottom - *y1) * relx / rely + *x1;*y2 = bottom;*visible = true;} else *visible = true;}void p2topleft(float* x1, float* y1, float* x2, float* y2, float left, float right, float bottom, float top, bool* visible){float leftproduct, topproduct;float relx, rely;relx = *x2 - *x1; rely = *y2 - *y1;leftproduct = (left - *x1) * rely;topproduct = (top - *y1) * relx;if (leftproduct < topproduct) {*x2 = (top - *y1) * relx / rely + *x1;*y2 = top;*visible = true;} else {*y2 = (left - *x1) * rely / relx + *y1;*x2 = left;*visible = true;} }