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POBox2D center of rotation
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copied!<p>I use Box2D as phisics engine and QtQuick as visualizer.</p> <p>I setted up simple scene with falling small rectangles and platform to test collisions</p> <pre><code>// the platform block Body { id: block bodyType: Body.Kinematic width:200 height:20 transformOrigin: Body.Center fixtures: Box { anchors.fill: parent friction: 1 density: 1 } Rectangle { anchors.fill: parent color: "yellow" border.color: "blue" } MouseArea { anchors.fill: parent onClicked: { block.rotation += 20 } } } </code></pre> <p>In QML I can set center of rotation:</p> <pre><code>transformOrigin: Body.Center </code></pre> <p>By default transformOrigin is top-left corner of object and in this case everything paintet fine. But when i move origin to center in QML it is going wrong as decribed at attached image </p> <p><img src="https://i.stack.imgur.com/oRy6B.png" alt="http://www.ruslan.pw/box2d.png"></p> <p>This is part of code when it get coords from Box2D and paint QML object</p> <pre><code>//getting coordination and angle of Box2D object const b2Vec2 position = mBody->GetPosition(); const float32 angle = mBody->GetAngle(); const qreal newX = position.x * scaleRatio; const qreal newY = -position.y * scaleRatio; const qreal newRotation = -(angle * 360.0) / (2 * b2_pi); // paint QML object at received coords setX(newX); setY(newY); setRotation(newRotation); </code></pre> <p>The problem is than Box2D rotates object with origin in top-left corner but QML object painted with origin in his center. So QML object is not syncronized with Box2D and falling rectangle painter in wrong place. I maked printscreen but actually box of Box2D is not visible, I added it to understand the problem.</p> <p>And my question - how can I set origin point in Box2D?</p>

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