OpenSceneGraph/examples/osgdepthpartition/DistanceAccumulator.cpp

360 lines
12 KiB
C++

/* OpenSceneGraph example, osgdepthpartion.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "DistanceAccumulator.h"
#include <osg/Geode>
#include <osg/Transform>
#include <osg/Projection>
#include <algorithm>
#include <math.h>
/** Function that sees whether one DistancePair should come before another in
an sorted list. Used to sort the vector of DistancePairs. */
bool precedes(const DistanceAccumulator::DistancePair &a,
const DistanceAccumulator::DistancePair &b)
{
// This results in sorting in order of descending far distances
if(a.second > b.second) return true;
else return false;
}
/** Computes distance betwen a point and the viewpoint of a matrix */
double distance(const osg::Vec3 &coord, const osg::Matrix& matrix)
{
return -( coord[0]*matrix(0,2) + coord[1]*matrix(1,2) +
coord[2]*matrix(2,2) + matrix(3,2) );
}
#define CURRENT_CLASS DistanceAccumulator
CURRENT_CLASS::CURRENT_CLASS()
: osg::NodeVisitor(TRAVERSE_ALL_CHILDREN),
_nearFarRatio(0.0005), _maxDepth(UINT_MAX)
{
setMatrices(osg::Matrix::identity(), osg::Matrix::identity());
reset();
}
CURRENT_CLASS::~CURRENT_CLASS() {}
void CURRENT_CLASS::pushLocalFrustum()
{
osg::Matrix& currMatrix = _viewMatrices.back();
// Compute the frustum in local space
osg::Polytope localFrustum;
localFrustum.setToUnitFrustum(false, false);
localFrustum.transformProvidingInverse(currMatrix*_projectionMatrices.back());
_localFrusta.push_back(localFrustum);
// Compute new bounding box corners
bbCornerPair corner;
corner.second = (currMatrix(0,2)<=0?1:0) |
(currMatrix(1,2)<=0?2:0) |
(currMatrix(2,2)<=0?4:0);
corner.first = (~corner.second)&7;
_bbCorners.push_back(corner);
}
void CURRENT_CLASS::pushDistancePair(double zNear, double zFar)
{
if(zFar > 0.0) // Make sure some of drawable is visible
{
// Make sure near plane is in front of viewpoint.
if(zNear <= 0.0)
{
zNear = zFar*_nearFarRatio;
if(zNear >= 1.0) zNear = 1.0; // 1.0 limit chosen arbitrarily!
}
// Add distance pair for current drawable
_distancePairs.push_back(DistancePair(zNear, zFar));
// Override the current nearest/farthest planes if necessary
if(zNear < _limits.first) _limits.first = zNear;
if(zFar > _limits.second) _limits.second = zFar;
}
}
/** Return true if the node should be traversed, and false if the bounding sphere
of the node is small enough to be rendered by one Camera. If the latter
is true, then store the node's near & far plane distances. */
bool CURRENT_CLASS::shouldContinueTraversal(osg::Node &node)
{
// Allow traversal to continue if we haven't reached maximum depth.
bool keepTraversing = (_currentDepth < _maxDepth);
const osg::BoundingSphere &bs = node.getBound();
double zNear = 0.0, zFar = 0.0;
// Make sure bounding sphere is valid and within viewing volume
if(bs.valid())
{
if(!_localFrusta.back().contains(bs)) keepTraversing = false;
else
{
// Compute near and far planes for this node
zNear = distance(bs._center, _viewMatrices.back());
zFar = zNear + bs._radius;
zNear -= bs._radius;
// If near/far ratio is big enough, then we don't need to keep
// traversing children of this node.
if(zNear >= zFar*_nearFarRatio) keepTraversing = false;
}
}
// If traversal should stop, then store this node's (near,far) pair
if(!keepTraversing) pushDistancePair(zNear, zFar);
return keepTraversing;
}
void CURRENT_CLASS::apply(osg::Node &node)
{
if(shouldContinueTraversal(node))
{
// Traverse this node
_currentDepth++;
traverse(node);
_currentDepth--;
}
}
void CURRENT_CLASS::apply(osg::Projection &proj)
{
if(shouldContinueTraversal(proj))
{
// Push the new projection matrix view frustum
_projectionMatrices.push_back(proj.getMatrix());
pushLocalFrustum();
// Traverse the group
_currentDepth++;
traverse(proj);
_currentDepth--;
// Reload original matrix and frustum
_localFrusta.pop_back();
_bbCorners.pop_back();
_projectionMatrices.pop_back();
}
}
void CURRENT_CLASS::apply(osg::Transform &transform)
{
if(shouldContinueTraversal(transform))
{
// Compute transform for current node
osg::Matrix currMatrix = _viewMatrices.back();
bool pushMatrix = transform.computeLocalToWorldMatrix(currMatrix, this);
if(pushMatrix)
{
// Store the new modelview matrix and view frustum
_viewMatrices.push_back(currMatrix);
pushLocalFrustum();
}
_currentDepth++;
traverse(transform);
_currentDepth--;
if(pushMatrix)
{
// Restore the old modelview matrix and view frustum
_localFrusta.pop_back();
_bbCorners.pop_back();
_viewMatrices.pop_back();
}
}
}
void CURRENT_CLASS::apply(osg::Geode &geode)
{
// Contained drawables will only be individually considered if we are
// allowed to continue traversing.
if(shouldContinueTraversal(geode))
{
osg::Drawable *drawable;
double zNear, zFar;
// Handle each drawable in this geode
for(unsigned int i = 0; i < geode.getNumDrawables(); i++)
{
drawable = geode.getDrawable(i);
const osg::BoundingBox &bb = drawable->getBound();
if(bb.valid())
{
// Make sure drawable will be visible in the scene
if(!_localFrusta.back().contains(bb)) continue;
// Compute near/far distances for current drawable
zNear = distance(bb.corner(_bbCorners.back().first),
_viewMatrices.back());
zFar = distance(bb.corner(_bbCorners.back().second),
_viewMatrices.back());
if(zNear > zFar) std::swap(zNear, zFar);
pushDistancePair(zNear, zFar);
}
}
}
}
void CURRENT_CLASS::setMatrices(const osg::Matrix &modelview,
const osg::Matrix &projection)
{
_modelview = modelview;
_projection = projection;
}
void CURRENT_CLASS::reset()
{
// Clear vectors & values
_distancePairs.clear();
_cameraPairs.clear();
_limits.first = DBL_MAX;
_limits.second = 0.0;
_currentDepth = 0;
// Initial transform matrix is the modelview matrix
_viewMatrices.clear();
_viewMatrices.push_back(_modelview);
// Set the initial projection matrix
_projectionMatrices.clear();
_projectionMatrices.push_back(_projection);
// Create a frustum without near/far planes, for cull computations
_localFrusta.clear();
_bbCorners.clear();
pushLocalFrustum();
}
void CURRENT_CLASS::computeCameraPairs()
{
// Nothing in the scene, so no cameras needed
if(_distancePairs.empty()) return;
// Entire scene can be handled by just one camera
if(_limits.first >= _limits.second*_nearFarRatio)
{
_cameraPairs.push_back(_limits);
return;
}
PairList::iterator i,j;
// Sort the list of distance pairs by descending far distance
std::sort(_distancePairs.begin(), _distancePairs.end(), precedes);
// Combine overlapping distance pairs. The resulting set of distance
// pairs (called combined pairs) will not overlap.
PairList combinedPairs;
DistancePair currPair = _distancePairs.front();
for(i = _distancePairs.begin(); i != _distancePairs.end(); i++)
{
// Current distance pair does not overlap current combined pair, so
// save the current combined pair and start a new one.
if(i->second < 0.99*currPair.first)
{
combinedPairs.push_back(currPair);
currPair = *i;
}
// Current distance pair overlaps current combined pair, so expand
// current combined pair to encompass distance pair.
else
currPair.first = std::min(i->first, currPair.first);
}
combinedPairs.push_back(currPair); // Add last pair
// Compute the (near,far) distance pairs for each camera.
// Each of these distance pairs is called a "view segment".
double currNearLimit, numSegs, new_ratio;
double ratio_invlog = 1.0/log(_nearFarRatio);
unsigned int temp;
for(i = combinedPairs.begin(); i != combinedPairs.end(); i++)
{
currPair = *i; // Save current view segment
// Compute the fractional number of view segments needed to span
// the current combined distance pair.
currNearLimit = currPair.second*_nearFarRatio;
if(currPair.first >= currNearLimit) numSegs = 1.0;
else
{
numSegs = log(currPair.first/currPair.second)*ratio_invlog;
// Compute the near plane of the last view segment
//currNearLimit *= pow(_nearFarRatio, -floor(-numSegs) - 1);
for(temp = (unsigned int)(-floor(-numSegs)); temp > 1; temp--)
{
currNearLimit *= _nearFarRatio;
}
}
// See if the closest view segment can absorb other combined pairs
for(j = i+1; j != combinedPairs.end(); j++)
{
// No other distance pairs can be included
if(j->first < currNearLimit) break;
}
// If we did absorb another combined distance pair, recompute the
// number of required view segments.
if(i != j-1)
{
i = j-1;
currPair.first = i->first;
if(currPair.first >= currPair.second*_nearFarRatio) numSegs = 1.0;
else numSegs = log(currPair.first/currPair.second)*ratio_invlog;
}
/* Compute an integer number of segments by rounding the fractional
number of segments according to how many segments there are.
In general, the more segments there are, the more likely that the
integer number of segments will be rounded down.
The purpose of this is to try to minimize the number of view segments
that are used to render any section of the scene without violating
the specified _nearFarRatio by too much. */
if(numSegs < 10.0) numSegs = floor(numSegs + 1.0 - 0.1*floor(numSegs));
else numSegs = floor(numSegs);
// Compute the near/far ratio that will be used for each view segment
// in this section of the scene.
new_ratio = pow(currPair.first/currPair.second, 1.0/numSegs);
// Add numSegs new view segments to the camera pairs list
for(temp = (unsigned int)numSegs; temp > 0; temp--)
{
currPair.first = currPair.second*new_ratio;
_cameraPairs.push_back(currPair);
currPair.second = currPair.first;
}
}
}
void CURRENT_CLASS::setNearFarRatio(double ratio)
{
if(ratio <= 0.0 || ratio >= 1.0) return;
_nearFarRatio = ratio;
}
#undef CURRENT_CLASS