static ParamSpec *paramp(PCStr(param),int nameonly){
int pi;
if( pi = paramX(param,nameonly) ){
return ¶ms[pi];
}
return 0;
}
GridIterator GridRay::begin() {
GridIterator result(*this);
double t;
// determine the value of t for which the ray enters the image
if (direction.x == 0) {
// special case
//std::cout << "vertical case" << std::endl;
if (!grid.contains(point(0))) {
throw std::runtime_error("outside grid");
}
result.t = -(double)(grid.height / 2);
result.x = trunc(point(0).x);
result.y = 0;
result.pos = GridIterator::BOTTOM;
try {
result.next();
if (!result.valid()) {
goto end;
}
return result;
} catch (std::exception& x) {
}
return end();
}
if (direction.y == 0) {
//std::cout << "horizontal case" << std::endl;
if (!grid.contains(point(0))) {
throw std::runtime_error("outside grid");
}
result.t = -(double)(grid.width / 2);
result.x = 0;
result.y = trunc(point(0).y);
result.pos = (direction.x > 0) ? GridIterator::LEFT : GridIterator::RIGHT;
try {
result.next();
if (!result.valid()) {
goto end;
}
//std::cout << "initialized horizontal iterator: " << *this << std::endl << result << std::endl;
return result;
} catch (std::exception& x) {
//std::cout << "no next point" << std::endl;
}
return end();
}
// normal case
t = paramX(0);
//std::cout << "paramX(0) = " << t << std::endl;
// left border is only possible if the direction points to the right
if ((direction.x > 0) && (t < 0)) {
GridPoint p = point(t);
if (p.y >= 0) {
result.t = t;
result.x = 0;
result.y = trunc(p.y);
result.pos = GridIterator::LEFT;
result.next();
if (!result.valid()) {
goto end;
}
return result;
}
}
// right boundary
t = paramX(grid.width);
//std::cout << "paramX(grid.width) = " << t << std::endl;
// right border is only possible if the direction points to the left
if ((direction.x < 0) && (t < 0)) {
GridPoint p = point(t);
if (p.y >= 0) {
result.t = t;
result.x = grid.width - 1;
result.y = trunc(p.y);
result.pos = GridIterator::RIGHT;
result.next();
if (!result.valid()) {
goto end;
}
return result;
}
}
// if we get to this point, the line we study must intersect
// the lower border
t = paramY(0);
//std::cout << "paramY(0) = " << t << std::endl;
if (t < 0) {
GridPoint p = point(t);
//std::cout << "Boundary point: " << p << std::endl;
if ((0 <= p.x + epsilon) && (p.x - epsilon< grid.width)) {
result.t = t;
result.x = trunc(p.x);
result.y = 0;
result.pos = GridIterator::BOTTOM;
//std::cout << "trying to get next from here: " << result << std::endl;
result.next();
if (!result.valid()) {
goto end;
}
return result;
}
}
t = paramX(grid.width);
//std::cout << "paramX(grid.width - 1) = " << t << std::endl;
if (t < 0) {
GridPoint p = point(t);
if (p.y >= 0) {
result.t = t;
result.x = grid.width - 1;
result.y = round(p.y);
result.pos = GridIterator::RIGHT;
result.next();
if (!result.valid()) {
goto end;
}
return result;
}
}
end:
result.x = -1;
result.y = -1;
return result;
}
