6

我有一个立方体元素在 3d 空间中旋转和平移。

我想在给定时间找出这个变换的rotateY部分。这可能吗？

我有：

var cube = document.getElementById("cube");
var transform = getComputedStyle(cube).webkitTransform;

//the value of transform is:
// matrix3d(-1, 0, 0.00000000000000012246467991473532, 0, 
//           0, 1, 0, 0, 
//          -0.00000000000000012246467991473532, 0, -1, 0, 
//           0, 0, 0, 1)

帮助？:-)

4

3 回答 3

4

如果您的对象仅围绕 Y 旋转，那么是的，旋转很容易计算 - 它是矩阵元素 1,1或 3,3 的 arccos 或 -(element 3,1) 的arsin 或元素 1 的 arcsin， 3. 在您的具体示例中，大约是 180 度。如果旋转不仅仅是 y 轴，那么您必须开始跟踪以前的旋转，它会变得更加混乱。

您的翻译将只是输出矩阵的底行，在这种情况下为 0,0,0。

请参阅 http://www.inversereality.org/tutorials/graphics%20programming/3dwmatrices.html上的示例

于 2012-05-15T15:07:29.160 回答
4

您可以使用“new WebKitCSSMatrix”功能检索转换信息。例如 ：

var matrix = new WebKitCSSMatrix($('#element').css('-webkit-transform'));
var translateZ = matrix.m43;

矩阵的每个部分都在这里解释：http: //9elements.com/html5demos/matrix3d/ 您可以检索更复杂的属性，如rotationX，用于带有数学混乱的3d矩阵：

var rotationX = Math.acos(matrix.a) * (180/Math.PI);
var rotationY = Math.asin(matrix.b) * (180/Math.PI);
于 2012-07-02T09:03:32.637 回答
3

给定函数确定rotation*，transform*并且scale对于给定的 DOM 元素跨浏览器。

如果你想要更多的东西，或者发现数学中的错误，可以在math.stackexchange.com上进行讨论

在http://caniuse.com/transforms3d中列出的浏览器上测试：

var reverseEngineerTransform3d = function (domElement, parameterName) {

        parameterName = parameterName.toLowerCase();

        var computedStyle = window.getComputedStyle(domElement),
            matrixStyle = computedStyle.transform || computedStyle.WebkitTransform || computedStyle.MozTransform || computedStyle.msTransform || computedStyle.OTransform;

        if (matrixStyle) {
            matrixStyle = matrixStyle.trim();
        }

        if (matrixStyle === 'none') {
            if (parameterName.indexOf('rotate') === 0) {
                return '0deg';
            } else if (parameterName.indexOf('translate') === 0) {
                return '0px';
            } else if (parameterName === 'scale') {
                return 1;
            } else {
                throw "Unsupported 3D parameter " + parameterName;
            }
        }

        else if (!matrixStyle || matrixStyle.substr(0, 9) !== 'matrix3d(') {
            //return something or die ?????
            throw "Something is wrong with 3D transform style. Probably no style applied at all OR unknown CSS3 vendor OR unknown/unsupported 3D matrix representation string OR CSS3 3D transform is not fully supported in this browser";
        }

        var matrix = window.WebKitCSSMatrix && (new WebKitCSSMatrix(matrixStyle)) ||
                window.MozCSSMatrix && (new MozCSSMatrix(matrixStyle)) ||
                window.MsCSSMatrix && (new MsCSSMatrix(matrixStyle)) ||
                window.OCSSMatrix && (new OCSSMatrix(matrixStyle)) ||
                window.CSSMatrix && (new CSSMatrix(matrixStyle)); // sorry 4 copy-paste my friends

        if (!matrix || isNaN(matrix.a) || isNaN(matrix.b) || isNaN(matrix.c) || isNaN(matrix.m41) || isNaN(matrix.m42) || isNaN(matrix.m43) || isNaN(matrix.m11)) {
            throw "Could not catch CSSMatrix constructor for current browser, OR the constructor has returned a non-standard matrix object (need .a, .b, .c and mXX numerical properties to work)";
        }


        // todo: giving a parameters array (and returning an array) is a good idea, or we could return everything if no parameters given

        switch (parameterName) {

            case 'rotatey':  // in degrees
                return Math.acos(matrix.m11)*180/Math.PI * (matrix.m13 > 0 ? -1 : 1) + 'deg';

            case 'rotatex':  // in degrees
                return Math.asin(matrix.m22)*180/Math.PI + 'deg';

            case 'rotatez':  // in degrees
                throw "TODO: Sorry, math people. I really need help here! Please implement this case for me. This will help you: http://9elements.com/html5demos/matrix3d/";

            case 'translatex': // in pixels
                return matrix.m41 + 'px';

            case 'translatey': // in pixels
                return matrix.m42 + 'px';

            case 'translatez': // in pixels
                return matrix.m43 + 'px';

            case 'scale': // no units
                if (matrix.m11 === matrix.m22 && matrix.m22 === matrix.m33) {
                    return matrix.m11;
                } else {
                    throw "I'm not so smart to calculate scale from this matrix";
                }

           // todo: anything else? skew ????

            default:
                throw "This function accepts 3d-parameter name (case-insensitive string) as the second argument. Currently supported: 'rotate[xyz]', 'translate[xyz]', 'scale'. This parameter is unsupported: " + parameterName;
        }
    };
于 2013-09-06T12:38:56.880 回答