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#include "csgtermnormalizer.h"
#include "csgterm.h"
#include "printutils.h"
/*!
NB! for e.g. empty intersections, this can normalize a tree to nothing and return NULL.
*/
shared_ptr<CSGTerm> CSGTermNormalizer::normalize(const shared_ptr<CSGTerm> &root)
{
this->aborted = false;
shared_ptr<CSGTerm> temp = root;
while (1) {
this->rootnode = temp;
this->nodecount = 0;
shared_ptr<CSGTerm> n = normalizePass(temp);
if (!n) return n; // If normalized to nothing
if (temp == n) break;
temp = n;
if (this->nodecount > this->limit) {
PRINTB("WARNING: Normalized tree is growing past %d elements. Aborting normalization.\n", this->limit);
// Clean up any partially evaluated terms
shared_ptr<CSGTerm> newroot = root, tmproot;
while (newroot && newroot != tmproot) {
tmproot = newroot;
newroot = collapse_null_terms(tmproot);
}
return newroot;
}
}
this->rootnode.reset();
return temp;
}
/*!
After aborting, a subtree might have become invalidated (NULL child term)
since terms can be instantiated multiple times.
This will search for NULL children an recursively repair the corresponding
subtree.
*/
shared_ptr<CSGTerm> CSGTermNormalizer::cleanup_term(shared_ptr<CSGTerm> &t)
{
if (t->type != CSGTerm::TYPE_PRIMITIVE) {
if (t->left) t->left = cleanup_term(t->left);
if (t->right) t->right = cleanup_term(t->right);
return collapse_null_terms(t);
}
else return t;
}
shared_ptr<CSGTerm> CSGTermNormalizer::normalizePass(shared_ptr<CSGTerm> term)
{
// This function implements the CSG normalization
// Reference:
// Goldfeather, J., Molnar, S., Turk, G., and Fuchs, H. Near
// Realtime CSG Rendering Using Tree Normalization and Geometric
// Pruning. IEEE Computer Graphics and Applications, 9(3):20-28,
// 1989.
// http://www.cc.gatech.edu/~turk/my_papers/pxpl_csg.pdf
if (term->type == CSGTerm::TYPE_PRIMITIVE) {
return term;
}
do {
while (term && match_and_replace(term)) { }
this->nodecount++;
if (nodecount > this->limit) {
PRINTB("WARNING: Normalized tree is growing past %d elements. Aborting normalization.\n", this->limit);
this->aborted = true;
return shared_ptr<CSGTerm>();
}
if (!term || term->type == CSGTerm::TYPE_PRIMITIVE) return term;
if (term->left) term->left = normalizePass(term->left);
} while (!this->aborted && term->type != CSGTerm::TYPE_UNION &&
((term->right && term->right->type != CSGTerm::TYPE_PRIMITIVE) ||
(term->left && term->left->type == CSGTerm::TYPE_UNION)));
if (!this->aborted) term->right = normalizePass(term->right);
// FIXME: Do we need to take into account any transformation of item here?
shared_ptr<CSGTerm> t = collapse_null_terms(term);
if (this->aborted) {
if (t) t = cleanup_term(t);
}
return t;
}
shared_ptr<CSGTerm> CSGTermNormalizer::collapse_null_terms(const shared_ptr<CSGTerm> &term)
{
if (!term->right) {
if (term->type == CSGTerm::TYPE_UNION || term->type == CSGTerm::TYPE_DIFFERENCE) return term->left;
else return term->right;
}
if (!term->left) {
if (term->type == CSGTerm::TYPE_UNION) return term->right;
else return term->left;
}
return term;
}
bool CSGTermNormalizer::match_and_replace(shared_ptr<CSGTerm> &term)
{
if (term->type == CSGTerm::TYPE_UNION || term->type == CSGTerm::TYPE_PRIMITIVE) {
return false;
}
// Part A: The 'x . (y . z)' expressions
shared_ptr<CSGTerm> x = term->left;
shared_ptr<CSGTerm> y = term->right->left;
shared_ptr<CSGTerm> z = term->right->right;
shared_ptr<CSGTerm> result = term;
// 1. x - (y + z) -> (x - y) - z
if (term->type == CSGTerm::TYPE_DIFFERENCE && term->right->type == CSGTerm::TYPE_UNION) {
term = CSGTerm::createCSGTerm(CSGTerm::TYPE_DIFFERENCE,
CSGTerm::createCSGTerm(CSGTerm::TYPE_DIFFERENCE, x, y),
z);
return true;
}
// 2. x * (y + z) -> (x * y) + (x * z)
else if (term->type == CSGTerm::TYPE_INTERSECTION && term->right->type == CSGTerm::TYPE_UNION) {
term = CSGTerm::createCSGTerm(CSGTerm::TYPE_UNION,
CSGTerm::createCSGTerm(CSGTerm::TYPE_INTERSECTION, x, y),
CSGTerm::createCSGTerm(CSGTerm::TYPE_INTERSECTION, x, z));
return true;
}
// 3. x - (y * z) -> (x - y) + (x - z)
else if (term->type == CSGTerm::TYPE_DIFFERENCE && term->right->type == CSGTerm::TYPE_INTERSECTION) {
term = CSGTerm::createCSGTerm(CSGTerm::TYPE_UNION,
CSGTerm::createCSGTerm(CSGTerm::TYPE_DIFFERENCE, x, y),
CSGTerm::createCSGTerm(CSGTerm::TYPE_DIFFERENCE, x, z));
return true;
}
// 4. x * (y * z) -> (x * y) * z
else if (term->type == CSGTerm::TYPE_INTERSECTION && term->right->type == CSGTerm::TYPE_INTERSECTION) {
term = CSGTerm::createCSGTerm(CSGTerm::TYPE_INTERSECTION,
CSGTerm::createCSGTerm(CSGTerm::TYPE_INTERSECTION, x, y),
z);
return true;
}
// 5. x - (y - z) -> (x - y) + (x * z)
else if (term->type == CSGTerm::TYPE_DIFFERENCE && term->right->type == CSGTerm::TYPE_DIFFERENCE) {
term = CSGTerm::createCSGTerm(CSGTerm::TYPE_UNION,
CSGTerm::createCSGTerm(CSGTerm::TYPE_DIFFERENCE, x, y),
CSGTerm::createCSGTerm(CSGTerm::TYPE_INTERSECTION, x, z));
return true;
}
// 6. x * (y - z) -> (x * y) - z
else if (term->type == CSGTerm::TYPE_INTERSECTION && term->right->type == CSGTerm::TYPE_DIFFERENCE) {
term = CSGTerm::createCSGTerm(CSGTerm::TYPE_DIFFERENCE,
CSGTerm::createCSGTerm(CSGTerm::TYPE_INTERSECTION, x, y),
z);
return true;
}
// Part B: The '(x . y) . z' expressions
x = term->left->left;
y = term->left->right;
z = term->right;
// 7. (x - y) * z -> (x * z) - y
if (term->left->type == CSGTerm::TYPE_DIFFERENCE && term->type == CSGTerm::TYPE_INTERSECTION) {
term = CSGTerm::createCSGTerm(CSGTerm::TYPE_DIFFERENCE,
CSGTerm::createCSGTerm(CSGTerm::TYPE_INTERSECTION, x, z),
y);
return true;
}
// 8. (x + y) - z -> (x - z) + (y - z)
else if (term->left->type == CSGTerm::TYPE_UNION && term->type == CSGTerm::TYPE_DIFFERENCE) {
term = CSGTerm::createCSGTerm(CSGTerm::TYPE_UNION,
CSGTerm::createCSGTerm(CSGTerm::TYPE_DIFFERENCE, x, z),
CSGTerm::createCSGTerm(CSGTerm::TYPE_DIFFERENCE, y, z));
return true;
}
// 9. (x + y) * z -> (x * z) + (y * z)
else if (term->left->type == CSGTerm::TYPE_UNION && term->type == CSGTerm::TYPE_INTERSECTION) {
term = CSGTerm::createCSGTerm(CSGTerm::TYPE_UNION,
CSGTerm::createCSGTerm(CSGTerm::TYPE_INTERSECTION, x, z),
CSGTerm::createCSGTerm(CSGTerm::TYPE_INTERSECTION, y, z));
return true;
}
return false;
}
// Counts all non-leaf nodes
unsigned int CSGTermNormalizer::count(const shared_ptr<CSGTerm> &term) const
{
if (!term) return 0;
return term->type == CSGTerm::TYPE_PRIMITIVE ? 0 : 1 + count(term->left) + count(term->right);
}
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