b2Math.cpp
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上传日期:2022-01-07
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- /*
- * Copyright (c) 2007-2009 Erin Catto http://www.gphysics.com
- *
- * This software is provided 'as-is', without any express or implied
- * warranty. In no event will the authors be held liable for any damages
- * arising from the use of this software.
- * Permission is granted to anyone to use this software for any purpose,
- * including commercial applications, and to alter it and redistribute it
- * freely, subject to the following restrictions:
- * 1. The origin of this software must not be misrepresented; you must not
- * claim that you wrote the original software. If you use this software
- * in a product, an acknowledgment in the product documentation would be
- * appreciated but is not required.
- * 2. Altered source versions must be plainly marked as such, and must not be
- * misrepresented as being the original software.
- * 3. This notice may not be removed or altered from any source distribution.
- */
- #include <Box2D/Common/b2Math.h>
- const b2Vec2 b2Vec2_zero(0.0f, 0.0f);
- const b2Mat22 b2Mat22_identity(1.0f, 0.0f, 0.0f, 1.0f);
- const b2Transform b2Transform_identity(b2Vec2_zero, b2Mat22_identity);
- /// Solve A * x = b, where b is a column vector. This is more efficient
- /// than computing the inverse in one-shot cases.
- b2Vec3 b2Mat33::Solve33(const b2Vec3& b) const
- {
- float32 det = b2Dot(col1, b2Cross(col2, col3));
- if (det != 0.0f)
- {
- det = 1.0f / det;
- }
- b2Vec3 x;
- x.x = det * b2Dot(b, b2Cross(col2, col3));
- x.y = det * b2Dot(col1, b2Cross(b, col3));
- x.z = det * b2Dot(col1, b2Cross(col2, b));
- return x;
- }
- /// Solve A * x = b, where b is a column vector. This is more efficient
- /// than computing the inverse in one-shot cases.
- b2Vec2 b2Mat33::Solve22(const b2Vec2& b) const
- {
- float32 a11 = col1.x, a12 = col2.x, a21 = col1.y, a22 = col2.y;
- float32 det = a11 * a22 - a12 * a21;
- if (det != 0.0f)
- {
- det = 1.0f / det;
- }
- b2Vec2 x;
- x.x = det * (a22 * b.x - a12 * b.y);
- x.y = det * (a11 * b.y - a21 * b.x);
- return x;
- }