Projection Camera Matrix

[theDream]

Does anyone know how the projectioncameramatrix is calculated in Leadwerks?

[Josh]

Same as GLUT does it:

//Make orthogonal projection matrix
	void Mat4::Ortho(const float left, const float right, const float top, const float bottom, const float znear, const float zfar)
	{
		i.x = 2.0f/(right-left);
		i.y = 0.0f;
		i.z = 0.0f;
		i.w = 0.0f;
		j.x = 0.0f;
		j.y = 2.0f/(top-bottom);
		j.z = 0.0f;
		j.w = 0.0f;
		k.x = 0.0f;
		k.y = 0.0f;
		k.z = 2.0f/(zfar-znear);
		k.w = 0.0f;
		t.x = -(right+left)/(right-left);
		t.y = -(top+bottom)/(top-bottom);
		t.z = -(zfar+znear)/(zfar-znear);
		t.w = 1.0f;
	}

void Mat4::Perspective(const float left, const float right, const float bottom, const float top, const float znear, const float zfar)
	{
		float A = (right+left)/(right-left);
		float B = (top+bottom)/(top-bottom);
		float C = -(zfar+znear)/(zfar-znear);
		float D = -(2.0*zfar*znear)/(zfar-znear);

		i.x = (2.0*znear)/(right-left);
		i.y = 0;
		i.z = 0;
		i.w = 0;
		j.x = 0;
		j.y = (2.0*znear)/(top-bottom);
		j.z = 0;
		j.w = 0;
		k.x = A;
		k.y = B;
		k.z = C;
		k.w = -1;
		t.x = 0;
		t.y = 0;
		t.z = D;
		t.w = 0;
	}

 

[theDream]

Thanks for the reply. I am having some issues calculating left, right, top, bottom. What I have researched says that  (bottom = -top).

But in your B calculation and the ones I have seen, top and bottom are added together. To me (top + bottom) should equal 0. But that is obviously not the case since there would be no need to calculate B since it would always be 0.

And thank you again for the help, I appreciate it.

[Josh]

I don't really understand the math, I just copied the code from the explanation in the OpenGL documentation.

In GL, the bottom/top might be the reverse of what you are expecting..