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CullingVolume.js
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CullingVolume.js
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define([
'./Cartesian3',
'./Cartesian4',
'./defaultValue',
'./defined',
'./DeveloperError',
'./Intersect',
'./Plane'
], function(
Cartesian3,
Cartesian4,
defaultValue,
defined,
DeveloperError,
Intersect,
Plane) {
'use strict';
/**
* The culling volume defined by planes.
*
* @alias CullingVolume
* @constructor
*
* @param {Cartesian4[]} [planes] An array of clipping planes.
*/
function CullingVolume(planes) {
/**
* Each plane is represented by a Cartesian4 object, where the x, y, and z components
* define the unit vector normal to the plane, and the w component is the distance of the
* plane from the origin.
* @type {Cartesian4[]}
* @default []
*/
this.planes = defaultValue(planes, []);
}
var faces = [new Cartesian3(), new Cartesian3(), new Cartesian3()];
Cartesian3.clone(Cartesian3.UNIT_X, faces[0]);
Cartesian3.clone(Cartesian3.UNIT_Y, faces[1]);
Cartesian3.clone(Cartesian3.UNIT_Z, faces[2]);
var scratchPlaneCenter = new Cartesian3();
var scratchPlaneNormal = new Cartesian3();
var scratchPlane = new Plane(new Cartesian3(1.0, 0.0, 0.0), 0.0);
/**
* Constructs a culling volume from a bounding sphere. Creates six planes that create a box containing the sphere.
* The planes are aligned to the x, y, and z axes in world coordinates.
*
* @param {BoundingSphere} boundingSphere The bounding sphere used to create the culling volume.
* @param {CullingVolume} [result] The object onto which to store the result.
* @returns {CullingVolume} The culling volume created from the bounding sphere.
*/
CullingVolume.fromBoundingSphere = function(boundingSphere, result) {
//>>includeStart('debug', pragmas.debug);
if (!defined(boundingSphere)) {
throw new DeveloperError('boundingSphere is required.');
}
//>>includeEnd('debug');
if (!defined(result)) {
result = new CullingVolume();
}
var length = faces.length;
var planes = result.planes;
planes.length = 2 * length;
var center = boundingSphere.center;
var radius = boundingSphere.radius;
var planeIndex = 0;
for (var i = 0; i < length; ++i) {
var faceNormal = faces[i];
var plane0 = planes[planeIndex];
var plane1 = planes[planeIndex + 1];
if (!defined(plane0)) {
plane0 = planes[planeIndex] = new Cartesian4();
}
if (!defined(plane1)) {
plane1 = planes[planeIndex + 1] = new Cartesian4();
}
Cartesian3.multiplyByScalar(faceNormal, -radius, scratchPlaneCenter);
Cartesian3.add(center, scratchPlaneCenter, scratchPlaneCenter);
plane0.x = faceNormal.x;
plane0.y = faceNormal.y;
plane0.z = faceNormal.z;
plane0.w = -Cartesian3.dot(faceNormal, scratchPlaneCenter);
Cartesian3.multiplyByScalar(faceNormal, radius, scratchPlaneCenter);
Cartesian3.add(center, scratchPlaneCenter, scratchPlaneCenter);
plane1.x = -faceNormal.x;
plane1.y = -faceNormal.y;
plane1.z = -faceNormal.z;
plane1.w = -Cartesian3.dot(Cartesian3.negate(faceNormal, scratchPlaneNormal), scratchPlaneCenter);
planeIndex += 2;
}
return result;
};
/**
* Determines whether a bounding volume intersects the culling volume.
*
* @param {Object} boundingVolume The bounding volume whose intersection with the culling volume is to be tested.
* @returns {Intersect} Intersect.OUTSIDE, Intersect.INTERSECTING, or Intersect.INSIDE.
*/
CullingVolume.prototype.computeVisibility = function(boundingVolume) {
//>>includeStart('debug', pragmas.debug);
if (!defined(boundingVolume)) {
throw new DeveloperError('boundingVolume is required.');
}
//>>includeEnd('debug');
var planes = this.planes;
var intersecting = false;
for (var k = 0, len = planes.length; k < len; ++k) {
var result = boundingVolume.intersectPlane(Plane.fromCartesian4(planes[k], scratchPlane));
if (result === Intersect.OUTSIDE) {
return Intersect.OUTSIDE;
} else if (result === Intersect.INTERSECTING) {
intersecting = true;
}
}
return intersecting ? Intersect.INTERSECTING : Intersect.INSIDE;
};
/**
* Determines whether a bounding volume intersects the culling volume.
*
* @param {Object} boundingVolume The bounding volume whose intersection with the culling volume is to be tested.
* @param {Number} parentPlaneMask A bit mask from the boundingVolume's parent's check against the same culling
* volume, such that if (planeMask & (1 << planeIndex) === 0), for k < 31, then
* the parent (and therefore this) volume is completely inside plane[planeIndex]
* and that plane check can be skipped.
* @returns {Number} A plane mask as described above (which can be applied to this boundingVolume's children).
*
* @private
*/
CullingVolume.prototype.computeVisibilityWithPlaneMask = function(boundingVolume, parentPlaneMask) {
//>>includeStart('debug', pragmas.debug);
if (!defined(boundingVolume)) {
throw new DeveloperError('boundingVolume is required.');
}
if (!defined(parentPlaneMask)) {
throw new DeveloperError('parentPlaneMask is required.');
}
//>>includeEnd('debug');
if (parentPlaneMask === CullingVolume.MASK_OUTSIDE || parentPlaneMask === CullingVolume.MASK_INSIDE) {
// parent is completely outside or completely inside, so this child is as well.
return parentPlaneMask;
}
// Start with MASK_INSIDE (all zeros) so that after the loop, the return value can be compared with MASK_INSIDE.
// (Because if there are fewer than 31 planes, the upper bits wont be changed.)
var mask = CullingVolume.MASK_INSIDE;
var planes = this.planes;
for (var k = 0, len = planes.length; k < len; ++k) {
// For k greater than 31 (since 31 is the maximum number of INSIDE/INTERSECTING bits we can store), skip the optimization.
var flag = (k < 31) ? (1 << k) : 0;
if (k < 31 && (parentPlaneMask & flag) === 0) {
// boundingVolume is known to be INSIDE this plane.
continue;
}
var result = boundingVolume.intersectPlane(Plane.fromCartesian4(planes[k], scratchPlane));
if (result === Intersect.OUTSIDE) {
return CullingVolume.MASK_OUTSIDE;
} else if (result === Intersect.INTERSECTING) {
mask |= flag;
}
}
return mask;
};
/**
* For plane masks (as used in {@link CullingVolume#computeVisibilityWithPlaneMask}), this special value
* represents the case where the object bounding volume is entirely outside the culling volume.
*
* @type {Number}
* @private
*/
CullingVolume.MASK_OUTSIDE = 0xffffffff;
/**
* For plane masks (as used in {@link CullingVolume.prototype.computeVisibilityWithPlaneMask}), this value
* represents the case where the object bounding volume is entirely inside the culling volume.
*
* @type {Number}
* @private
*/
CullingVolume.MASK_INSIDE = 0x00000000;
/**
* For plane masks (as used in {@link CullingVolume.prototype.computeVisibilityWithPlaneMask}), this value
* represents the case where the object bounding volume (may) intersect all planes of the culling volume.
*
* @type {Number}
* @private
*/
CullingVolume.MASK_INDETERMINATE = 0x7fffffff;
return CullingVolume;
});