/indra/llmath/llline.cpp
C++ | 196 lines | 100 code | 29 blank | 67 comment | 4 complexity | d64fc11b1feb080c3ab92d0c99b67a48 MD5 | raw file
Possible License(s): LGPL-2.1
- /**
- * @file llline.cpp
- * @author Andrew Meadows
- * @brief Simple line class that can compute nearest approach between two lines
- *
- * $LicenseInfo:firstyear=2006&license=viewerlgpl$
- * Second Life Viewer Source Code
- * Copyright (C) 2010, Linden Research, Inc.
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation;
- * version 2.1 of the License only.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
- * $/LicenseInfo$
- */
- #include "linden_common.h"
- #include "llline.h"
- #include "llrand.h"
- const F32 SOME_SMALL_NUMBER = 1.0e-5f;
- const F32 SOME_VERY_SMALL_NUMBER = 1.0e-8f;
- LLLine::LLLine()
- : mPoint(0.f, 0.f, 0.f),
- mDirection(1.f, 0.f, 0.f)
- { }
- LLLine::LLLine( const LLVector3& first_point, const LLVector3& second_point )
- {
- setPoints(first_point, second_point);
- }
- void LLLine::setPoints( const LLVector3& first_point, const LLVector3& second_point )
- {
- mPoint = first_point;
- mDirection = second_point - first_point;
- mDirection.normalize();
- }
- void LLLine::setPointDirection( const LLVector3& first_point, const LLVector3& second_point )
- {
- setPoints(first_point, first_point + second_point);
- }
- bool LLLine::intersects( const LLVector3& point, F32 radius ) const
- {
- LLVector3 other_direction = point - mPoint;
- LLVector3 nearest_point = mPoint + mDirection * (other_direction * mDirection);
- F32 nearest_approach = (nearest_point - point).length();
- return (nearest_approach <= radius);
- }
- // returns the point on this line that is closest to some_point
- LLVector3 LLLine::nearestApproach( const LLVector3& some_point ) const
- {
- return (mPoint + mDirection * ((some_point - mPoint) * mDirection));
- }
- // the accuracy of this method sucks when you give it two nearly
- // parallel lines, so you should probably check for parallelism
- // before you call this
- //
- // returns the point on this line that is closest to other_line
- LLVector3 LLLine::nearestApproach( const LLLine& other_line ) const
- {
- LLVector3 between_points = other_line.mPoint - mPoint;
- F32 dir_dot_dir = mDirection * other_line.mDirection;
- F32 one_minus_dir_dot_dir = 1.0f - fabs(dir_dot_dir);
- if ( one_minus_dir_dot_dir < SOME_VERY_SMALL_NUMBER )
- {
- #ifdef LL_DEBUG
- llwarns << "LLLine::nearestApproach() was given two very "
- << "nearly parallel lines dir1 = " << mDirection
- << " dir2 = " << other_line.mDirection << " with 1-dot_product = "
- << one_minus_dir_dot_dir << llendl;
- #endif
- // the lines are approximately parallel
- // We shouldn't fall in here because this check should have been made
- // BEFORE this function was called. We dare not continue with the
- // computations for fear of division by zero, but we have to return
- // something so we return a bogus point -- caller beware.
- return 0.5f * (mPoint + other_line.mPoint);
- }
- F32 odir_dot_bp = other_line.mDirection * between_points;
- F32 numerator = 0;
- F32 denominator = 0;
- for (S32 i=0; i<3; i++)
- {
- F32 factor = dir_dot_dir * other_line.mDirection.mV[i] - mDirection.mV[i];
- numerator += ( between_points.mV[i] - odir_dot_bp * other_line.mDirection.mV[i] ) * factor;
- denominator -= factor * factor;
- }
- F32 length_to_nearest_approach = numerator / denominator;
- return mPoint + length_to_nearest_approach * mDirection;
- }
- std::ostream& operator<<( std::ostream& output_stream, const LLLine& line )
- {
- output_stream << "{point=" << line.mPoint << "," << "dir=" << line.mDirection << "}";
- return output_stream;
- }
- F32 ALMOST_PARALLEL = 0.99f;
- F32 TOO_SMALL_FOR_DIVISION = 0.0001f;
- // returns 'true' if this line intersects the plane
- // on success stores the intersection point in 'result'
- bool LLLine::intersectsPlane( LLVector3& result, const LLLine& plane ) const
- {
- // p = P + l * d equation for a line
- //
- // N * p = D equation for a point
- //
- // N * (P + l * d) = D
- // N*P + l * (N*d) = D
- // l * (N*d) = D - N*P
- // l = ( D - N*P ) / ( N*d )
- //
- F32 dot = plane.mDirection * mDirection;
- if (fabs(dot) < TOO_SMALL_FOR_DIVISION)
- {
- return false;
- }
- F32 plane_dot = plane.mDirection * plane.mPoint;
- F32 length = ( plane_dot - (plane.mDirection * mPoint) ) / dot;
- result = mPoint + length * mDirection;
- return true;
- }
- //static
- // returns 'true' if planes intersect, and stores the result
- // the second and third arguments are treated as planes
- // where mPoint is on the plane and mDirection is the normal
- // result.mPoint will be the intersection line's closest approach
- // to first_plane.mPoint
- bool LLLine::getIntersectionBetweenTwoPlanes( LLLine& result, const LLLine& first_plane, const LLLine& second_plane )
- {
- // TODO -- if we ever get some generic matrix solving code in our libs
- // then we should just use that, since this problem is really just
- // linear algebra.
- F32 dot = fabs(first_plane.mDirection * second_plane.mDirection);
- if (dot > ALMOST_PARALLEL)
- {
- // the planes are nearly parallel
- return false;
- }
- LLVector3 direction = first_plane.mDirection % second_plane.mDirection;
- direction.normalize();
- LLVector3 first_intersection;
- {
- LLLine intersection_line(first_plane);
- intersection_line.mDirection = direction % first_plane.mDirection;
- intersection_line.mDirection.normalize();
- intersection_line.intersectsPlane(first_intersection, second_plane);
- }
- /*
- LLVector3 second_intersection;
- {
- LLLine intersection_line(second_plane);
- intersection_line.mDirection = direction % second_plane.mDirection;
- intersection_line.mDirection.normalize();
- intersection_line.intersectsPlane(second_intersection, first_plane);
- }
- */
- result.mPoint = first_intersection;
- result.mDirection = direction;
- return true;
- }