SpaceCadetPinball/SpaceCadetPinball/proj.cpp

#include "pch.h"
#include "proj.h"

mat4_row_major proj::matrix;
float proj::d_, proj::centerx, proj::centery;

void proj::init(float* mat4x3, float d, float centerX, float centerY)
{
	/*for (auto colIndex = 0; colIndex < 4; ++colIndex)
	{
		// Todo: out of bounds read from mat4x3?
		for (int rowIndex = colIndex, i = 4; i > 0; rowIndex += 4, --i)
		{
			((float*)&matrix)[rowIndex] = mat4x3[rowIndex];
		}
	}*/
	memcpy(&matrix, mat4x3, sizeof(float) * 4 * 3);

	matrix.Row3.X = 0.0;
	matrix.Row3.Y = 0.0;
	matrix.Row3.Z = 0.0;
	matrix.Row3.W = 1.0;

	d_ = d;
	centerx = centerX;
	centery = centerY;
}

vector3 proj::matrix_vector_multiply(const mat4_row_major& mat, const vector3& vec)
{
	vector3 dstVec;
	const float x = vec.X, y = vec.Y, z = vec.Z;
	dstVec.X = z * mat.Row0.Z + y * mat.Row0.Y + x * mat.Row0.X + mat.Row0.W;
	dstVec.Y = z * mat.Row1.Z + y * mat.Row1.Y + x * mat.Row1.X + mat.Row1.W;
	dstVec.Z = z * mat.Row2.Z + y * mat.Row2.Y + x * mat.Row2.X + mat.Row2.W;
	return dstVec;
}

float proj::z_distance(const vector3& vec)
{
	auto projVec = matrix_vector_multiply(matrix, vec);
	return maths::magnitude(projVec);
}

vector2i proj::xform_to_2d(const vector2& vec)
{
	vector3 vec3{ vec.X, vec.Y, 0 };
	return xform_to_2d(vec3);
}

vector2i proj::xform_to_2d(const vector3& vec)
{
	float projCoef;

	auto projVec = matrix_vector_multiply(matrix, vec);
	if (projVec.Z == 0.0f)
		projCoef = 999999.88f;
	else
		projCoef = d_ / projVec.Z;
	return
	{
		static_cast<int>(projVec.X * projCoef + centerx),
		static_cast<int>(projVec.Y * projCoef + centery)
	};
}

void proj::recenter(float centerX, float centerY)
{
	centerx = centerX;
	centery = centerY;
}