More geometry instance attributes

[pjcozzi]

Currently only per-instance color and show are supported for geometries. Cesium needs classes to represent generic data like the two examples below.

var FloatInstanceAttribute = function(value) {
    value = Cesium.defaultValue(value, 0.0);

    this.value = FloatInstanceAttribute.toValue(value);
};

Cesium.defineProperties(FloatInstanceAttribute.prototype, {
    componentDatatype : {
        get : function() {
            return Cesium.ComponentDatatype.FLOAT;
        }
    },
    componentsPerAttribute : {
        get : function() {
            return 1;
        }
    },
    normalize : {
        get : function() {
            return false;
        }
    }
});

FloatInstanceAttribute.toValue = function(value, result) {
    //>>includeStart('debug', pragmas.debug);
    if (!Cesium.defined(value)) {
        throw new Cesium.DeveloperError('value is required.');
    }
    //>>includeEnd('debug');

    if (!Cesium.defined(result)) {
        return new Float32Array([value]);
    }
    result[0] = value;
    return result;
};

var Cartesian3InstanceAttribute = function(x, y, z) {
    this.value = new Float32Array([
        Cesium.defaultValue(x, 0.0),
        Cesium.defaultValue(y, 0.0),
        Cesium.defaultValue(z, 0.0)
    ]);
};

Cesium.defineProperties(Cartesian3InstanceAttribute.prototype, {
    componentDatatype : {
        get : function() {
            return Cesium.ComponentDatatype.FLOAT;
        }
    },
    componentsPerAttribute : {
        get : function() {
            return 3;
        }
    },
    normalize : {
        get : function() {
            return false;
        }
    }
});

Cartesian3InstanceAttribute.fromCartesian3 = function(cartesian) {
    //>>includeStart('debug', pragmas.debug);
    if (!Cesium.defined(cartesian)) {
        throw new Cesium.DeveloperError('cartesian is required.');
    }
    //>>includeEnd('debug');
    return new Cartesian3InstanceAttribute(cartesian.x, cartesian.y, cartesian.z);
};

Cartesian3InstanceAttribute.toValue = function(cartesian, result) {
    //>>includeStart('debug', pragmas.debug);
    if (!Cesium.defined(cartesian)) {
        throw new Cesium.DeveloperError('cartesian is required.');
    }
    //>>includeEnd('debug');

    if (!Cesium.defined(result)) {
        return new Float32Array([cartesian.x, cartesian.y, cartesian.z]);
    }
    result[0] = cartesian.x;
    result[1] = cartesian.y;
    result[2] = cartesian.z;
    return result;
};

CC #766

[pjcozzi]

Also the toValue functions throughout should require result.

[ggetz]

This is unlikely to become a priority anytime soon. We'd still happily accept a PR addressing this issue. But tracking this isn't particularly useful because of its low priority, so I will close it. Thanks!