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[blok] / Box2D / Source / Common / b2Math.cpp

diff --git a/Box2D/Source/Common/b2Math.cpp b/Box2D/Source/Common/b2Math.cpp
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+/*
+* Copyright (c) 2007 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 "b2Math.h"
+
+const b2Vec2 b2Vec2_zero(0.0f, 0.0f);
+const b2Mat22 b2Mat22_identity(1.0f, 0.0f, 0.0f, 1.0f);
+const b2XForm b2XForm_identity(b2Vec2_zero, b2Mat22_identity);
+
+void b2Sweep::GetXForm(b2XForm* xf, float32 t) const
+{
+       // center = p + R * localCenter
+       if (1.0f - t0 > B2_FLT_EPSILON)
+       {
+               float32 alpha = (t - t0) / (1.0f - t0);
+               xf->position = (1.0f - alpha) * c0 + alpha * c;
+               float32 angle = (1.0f - alpha) * a0 + alpha * a;
+               xf->R.Set(angle);
+       }
+       else
+       {
+               xf->position = c;
+               xf->R.Set(a);
+       }
+
+       // Shift to origin
+       xf->position -= b2Mul(xf->R, localCenter);
+}
+
+void b2Sweep::Advance(float32 t)
+{
+       if (t0 < t && 1.0f - t0 > B2_FLT_EPSILON)
+       {
+               float32 alpha = (t - t0) / (1.0f - t0);
+               c0 = (1.0f - alpha) * c0 + alpha * c;
+               a0 = (1.0f - alpha) * a0 + alpha * a;
+               t0 = t;
+       }
+}