Hey, I have a problem with those Algorithms from my other post, and I have tried all I can to figure out what is not working, so I am just gonna post the code here. Sorry, but I don''t know how to do that neat, text parsing stuff: // FindIntersection(coords for 2 lines) : This function returns the point where the two specified lines intersect. 2D return POINT FindIntersection(int l1x1, int l1y1, int l1x2, int l1y2, int l2x1, int l2y1, int l2x2, int l2y2, DWORD *pIntersectionType) { POINT Line11; // Line 1 Point 1 POINT Line12; // Line 1 Point 2 long double Line1m; // Line 1 slope long double Line1b; // Line 1 y-intercept POINT Line21; // Line 2 Point 1 POINT Line22; // Line 2 Point 2 long double Line2m; // Line 2 slope long double Line2b; // Line 2 y-intercept POINT Inter; // The point where the lines intercept Inter.x = 0; Inter.y = 0; // Put the lines in the proper algebraeic format if(l1x1 < l1x2) { Line11.x = l1x1; Line11.y = l1y1; Line12.x = l1x2; Line12.y = l1y2; } else { Line11.x = l1x2; Line11.y = l1y2; Line12.x = l1x1; Line12.y = l1y1; } if(l2x1 < l2x2) { Line21.x = l2x1; Line21.y = l2y1; Line22.x = l2x2; Line22.y = l2y2; } else { Line21.x = l2x2; Line21.y = l2y2; Line22.x = l2x1; Line22.y = l2y1; } // When both lines are neither vertical or horizontal if(Line12.y != Line11.y && Line12.x != Line11.x && Line22.y != Line21.y && Line22.x != Line21.x) { if(pIntersectionType != NULL) *pIntersectionType = GD_NEITHER_H_V; Line1m = (Line12.y - Line11.y) / (Line12.x - Line11.x); Line2m = (Line22.y - Line21.y) / (Line22.x - Line21.x); Line1b = Line11.y - (Line1m * Line11.x); Line2b = Line21.y - (Line2m * Line21.x); Inter.x = (Line1b - Line2b) / (Line2m - Line1m); Inter.y = Line1m * Inter.x + Line1b; } // When one line is vertical and one is horizontal else if(Line12.y == Line11.y && Line22.x == Line21.x) { if(pIntersectionType != NULL) *pIntersectionType = GD_BOTH_H_V; Inter.x = Line21.x; Inter.y = Line11.y; } else if(Line22.y == Line21.y && Line12.x == Line11.x) { if(pIntersectionType != NULL) *pIntersectionType = GD_BOTH_H_V; Inter.x = Line11.x; Inter.y = Line21.y; } // When one line is horizontal and one is not else if(Line12.y == Line11.y && Line22.y != Line21.y) { if(pIntersectionType != NULL) *pIntersectionType = GD_ONE_H_V; Line1m = 0; Line2m = (Line22.y - Line21.y) / (Line22.x - Line21.x); Line1b = Line11.y; Line2b = Line21.y - (Line2m * Line21.x); Inter.x = (Line1b - Line2b) / (Line2m - Line1m); Inter.y = Line12.y; } else if(Line22.y == Line21.y && Line12.y != Line11.y) { if(pIntersectionType != NULL) *pIntersectionType = GD_ONE_H_V; Line1m = (Line12.y - Line11.y) / (Line12.x - Line11.x); Line2m = 0; Line1b = Line11.y - (Line1m * Line11.x); Line2b = Line21.y; Inter.x = (Line1b - Line2b) / (Line2m - Line1m); Inter.y = Line22.y; } // When one line is vertical and one is not else if(Line12.x == Line11.x && Line22.x != Line21.x) { if(pIntersectionType != NULL) *pIntersectionType = GD_ONE_H_V; Line2m = (Line22.y - Line21.y) / (Line22.x - Line21.x); Line2b = Line21.y - (Line2m * Line21.x); Inter.x = Line12.x; Inter.y = Line2m * Line12.x + Line2b; } else if(Line22.x == Line21.x && Line12.x != Line11.x) { if(pIntersectionType != NULL) *pIntersectionType = GD_ONE_H_V; Line1m = (Line12.y - Line11.y) / (Line12.x - Line11.x); Line1b = Line11.y - (Line1m * Line11.x); Inter.x = Line22.x; Inter.y = Line1m * Line22.x + Line1b; } else if(pIntersectionType != NULL) *pIntersectionType = GD_DONT_INTERSECT; return Inter; } There it is! I am hoping all you code/math sharks out there will be able to tell me my predicament. A problem with trying to find the intercept between a horizontal line, and a line that is mostly horizontal(the line has very litle change along the y axis). If anyone could help me, I would be very grateful. BTW: Sorry about the new post Brent Robinson "Ich bin deinem Vatter!"

For an another look at intersection of two lines check out Paul Bourke''s website or visit mine for the link. I''ve done intersection with parametric equation so look at my csg code for that also. It''s rather longish so I won''t post it here. The equation doesn''t use slopes. My code uses Paul''s equation.

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