FGFS-4.1/simgear
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Manuel Massing:

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Attached is a small fix for the sorting in CloudShaderGeometry.cxx.
I think the sorting problem stems from the osg idiosyncracy
to store transposed matrices...so the intuitive

       osg::Vec4f p = vm * osg::Vec4f(_cloudsprites[i]->position.osg(), 1.0f);

needs to be replaced with...

       osg::Vec4f p = vm.preMult(osg::Vec4f(_cloudsprites[i]->position.osg(), 1.0f);

The patch also optimizes the distance calculation - it evaluates the distances
in model space instead of eye space, which reduces computation to a dot-
product instead of a matrix multiplication.
This commit is contained in:
curt
2008-11-09 15:39:54 +00:00
parent 0b8b6ac56a
commit e6371cbf9c
1 changed files with 15 additions and 10 deletions
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25
simgear/scene/sky/CloudShaderGeometry.cxx
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@@ -34,27 +34,32 @@ namespace simgear
{
void CloudShaderGeometry::drawImplementation(RenderInfo& renderInfo) const
{
if (!_cloudsprites.size()) return;
osg::State& state = *renderInfo.getState();
osg::Matrix vm = state.getModelViewMatrix();
//TODO: It isn't clear whether this is worth the perf hit ATM.
// Do a single iteration of a bubble sort. We do this in reverse
// so that elements closest to the camera bubble to the front than
// the elements further away
for(int i = (_cloudsprites.size() -2); i >= 0; i--)
// Transform the viewing direction, represented by the eye space vector (0,0,-1, 0), into model-space
// (here we simply take the opposite direction and reverse the ordering when sorting)
osg::Vec3f view_dir(vm(0, 2), vm(1, 2), vm(2, 2)); // Caveat: OpenSceneGraph matrices are transposed!
float p = view_dir*_cloudsprites[0]->position.osg();
// Do a single iteration of a bubble sort, sorting
// back to front.
for(int i = 0; i < _cloudsprites.size() - 1; i++)
{
osg::Vec4f p = vm * osg::Vec4f(_cloudsprites[i]->position.osg(), 1.0f);
osg::Vec4f q = vm * osg::Vec4f(_cloudsprites[i+1]->position.osg(), 1.0f);
if (p.z() > q.z())
{
float q = view_dir*_cloudsprites[i+1]->position.osg();
if (p > q) {
CloudSprite c = *_cloudsprites[i];
*_cloudsprites[i] = *_cloudsprites[i+1];
*_cloudsprites[i+1] = c;
}
else
p = q;
}
const Extensions* extensions = getExtensions(state.getContextID(),true);
for(CloudSpriteList::const_iterator t = _cloudsprites.begin(); t != _cloudsprites.end(); ++t)