C++ Simple calculation outputting 0.0000000000000000 instead of 0.003333 - c++

Question

The calculation for dx and dy is returning 0 and I don't see what the issue is. The console seems to show all the correct values are being used.
void drawBackground()
{
double r, g, b, dx, dy, Wx, Wy, Wz;
Ray ray;
cout << "xmax: " << sceneDescription::imagePlaneXmax << " xmin: " << sceneDescription::imagePlaneXmin << endl;
cout << "ymax: " << sceneDescription::imagePlaneYmax << " ymin: " << sceneDescription::imagePlaneYmin << endl;
cout << "Iw: " << sceneDescription::Iw << " Ih: " << sceneDescription::Ih << endl;
cout << " " << endl;
dx = (sceneDescription::imagePlaneXmax - (sceneDescription::imagePlaneXmin))/sceneDescription::Iw;
dy = (sceneDescription::imagePlaneYmax - (sceneDescription::imagePlaneYmin))/sceneDescription::Ih;
std::cout << "dx: "<< boost::format("%1$.16f") % dx << " dy: "<< boost::format("%1$.16f") % dy << endl;
}
sceneDescription.h
#include <glm/glm.hpp>
using namespace glm;
class sceneDescription{
public:
static const int imagePlaneXmin = -1;
static const int imagePlaneXmax = 1;
static const int imagePlaneYmin = -1;
static const int imagePlaneYmax = 1;
static const int Iw = 600;
static const int Ih = 800;
};
Console output:
xmax: 1 xmin: -1
ymax: 1 ymin: -1
Iw: 600 Ih: 800
dx: 0.0000000000000000 dy: 0.0000000000000000

Answer 1

The problem is that the statement:
dx = (sceneDescription::imagePlaneXmax -
(sceneDescription::imagePlaneXmin))/sceneDescription::Iw;
will give the following result:
(1-(-1))/600 = 2/600 = 0.00 (since this is integer division).
You may want to cast the number to double.
Something like this would work:
dx = (double)(sceneDescription::imagePlaneXmax -
(sceneDescription::imagePlaneXmin)) / sceneDescription::Iw;
Since cast operator has higher priority than division, the numerator will be cast by (double) and the denominator will be cast implicitly giving the double result.
Hope that helps!