Frustum backwards?

[hallow flint]

I followed a bit of this tutorial: http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-extracting-the-planes/

Calculations:

drx::util::SPOT nCenter = this->position.Subs(this->front.Multiply(drx::gfx::ogl::n));
drx::util::SPOT fCenter = this->position.Subs(this->front.Multiply(drx::gfx::ogl::f));

double nHeight = 2.0 * tan(drx::math::Radians(this->zoom) * 0.5) * drx::gfx::ogl::n;
double fHeight = 2.0 * tan(drx::math::Radians(this->zoom) * 0.5) * drx::gfx::ogl::f;
double nWidth = nHeight * drx::gfx::ogl::ar;
double fWidth = fHeight * drx::gfx::ogl::ar;

frustum.backLeftTop = fCenter.Add(this->up.Multiply(fHeight * 0.5)).Subs(this->right.Multiply(fWidth * 0.5));
frustum.backRightTop = fCenter.Add(this->up.Multiply(fHeight * 0.5)).Add(this->right.Multiply(fWidth * 0.5));
frustum.backLeftBottom = fCenter.Subs(this->up.Multiply(fHeight * 0.5)).Subs(this->right.Multiply(fWidth * 0.5));
frustum.backRightBottom = fCenter.Subs(this->up.Multiply(fHeight * 0.5)).Add(this->right.Multiply(fWidth * 0.5));
frustum.frontLeftTop = nCenter.Add(this->up.Multiply(nHeight * 0.5)).Subs(this->right.Multiply(nWidth * 0.5));
frustum.frontRightTop = nCenter.Add(this->up.Multiply(nHeight * 0.5)).Add(this->right.Multiply(nWidth * 0.5));
frustum.frontLeftBottom = nCenter.Subs(this->up.Multiply(nHeight * 0.5)).Subs(this->right.Multiply(nWidth * 0.5));
frustum.frontRightBottom = nCenter.Subs(this->up.Multiply(nHeight * 0.5)).Add(this->right.Multiply(nWidth * 0.5));

Front of the frustum appears as a small, really small rectangle in front as it should, but back plane is like, behind the camera? Not sure my calculations are correct?

[warm tree]

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[hallow flint]

Front of the frustum, blue rectangle. Wee bit zoomed in to see it.

I can get it to reverse, by dividing the back plane with their respective W values and then multiplying by for example the far Z ( 2000.0 ), then it shows up correctly, but I'm not sure I should do that?

Corner dumps:

// back
> X 525.469, Y 1945.39, Z 2060.18, W -1413.21
> X 1094.35, Y 482.475, Z 2590.67, W -1413.21
> X 2600.98, Y 482.475, Z 975.009, W -1413.21
> X 2032.1, Y 1945.39, Z 444.519, W -1413.21
---
// front
> X 649.994, Y 550.07, Z 666.07, W 0.929289
> X 650.022, Y 549.997, Z 666.096, W 0.929289
> X 650.098, Y 549.997, Z 666.015, W 0.929289
> X 650.069, Y 550.07, Z 665.989, W 0.929289