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https://github.com/k4zmu2a/SpaceCadetPinball.git
synced 2024-11-17 15:20:17 +01:00
105 lines
3 KiB
C++
105 lines
3 KiB
C++
#include "pch.h"
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#include "proj.h"
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mat4_row_major proj::matrix;
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float proj::d_, proj::centerx, proj::centery;
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void proj::init(float* mat4x3, float d, float centerX, float centerY)
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{
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/*for (auto colIndex = 0; colIndex < 4; ++colIndex)
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{
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// Todo: out of bounds read from mat4x3?
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for (int rowIndex = colIndex, i = 4; i > 0; rowIndex += 4, --i)
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{
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((float*)&matrix)[rowIndex] = mat4x3[rowIndex];
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}
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}*/
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memcpy(&matrix, mat4x3, sizeof(float) * 4 * 3);
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matrix.Row3.X = 0.0;
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matrix.Row3.Y = 0.0;
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matrix.Row3.Z = 0.0;
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matrix.Row3.W = 1.0;
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d_ = d;
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centerx = centerX;
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centery = centerY;
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}
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vector3 proj::matrix_vector_multiply(const mat4_row_major& mat, const vector3& vec)
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{
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vector3 dstVec;
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const float x = vec.X, y = vec.Y, z = vec.Z;
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dstVec.X = z * mat.Row0.Z + y * mat.Row0.Y + x * mat.Row0.X + mat.Row0.W;
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dstVec.Y = z * mat.Row1.Z + y * mat.Row1.Y + x * mat.Row1.X + mat.Row1.W;
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dstVec.Z = z * mat.Row2.Z + y * mat.Row2.Y + x * mat.Row2.X + mat.Row2.W;
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return dstVec;
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}
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float proj::z_distance(const vector3& vec)
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{
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auto projVec = matrix_vector_multiply(matrix, vec);
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return maths::magnitude(projVec);
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}
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vector2i proj::xform_to_2d(const vector2& vec)
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{
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vector3 vec3{ vec.X, vec.Y, 0 };
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return xform_to_2d(vec3);
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}
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vector3 proj::ReverseXForm(const vector2i& vec)
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{
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// Pinball perspective projection matrix, the same for all tables resolutions:
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// X: 1.000000 Y: 0.000000 Z: 0.000000 W: 0.000000
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// X: 0.000000 Y: -0.913545 Z: 0.406737 W: 3.791398
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// X: 0.000000 Y: -0.406737 Z: -0.913545 W: 24.675402
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// X: 0.000000 Y: 0.000000 Z: 0.000000 W: 1.000000
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// Let A = -0.913545, B = 0.406737, F = 3.791398, G = 24.675402
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// Then forward projection can be expressed as:
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// x1 = x0
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// y1 = y0 * A + z0 * B + F
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// z1 = -y0 * B + z0 * A + G
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// x2 = x1 / z1 = x0 / z1
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// y2 = y1 / z1
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// z2 = z1 / z1 = 1
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// Reverse projection: find x0, y0, z0 given x2 and y2
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// y0 from y2 and z0, based on substitution in y2 = y1 / z1
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// y0 = (y2 * (A * z0 + G) - B * z0 - F)/(A + B * y2)
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// x0 from x2, y0 and z0, based on substitution in x2 = x0 / z1
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// x0 = (x2 * (A * z0 - B * y0 + G)
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// This pair of equations is solvable with fixed z0; most commonly z0 = 0
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// PB projection also includes scaling and offset, this can be undone before the main calculations
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// x2 = x0 * D / z1 + cX
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// x0 = ((x2 - cX) / D) * z1
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const auto A = matrix.Row1.Y, B = matrix.Row1.Z, F = matrix.Row1.W, G = matrix.Row2.W, D = d_;
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const auto x2 = (vec.X - centerx) /D, y2 = (vec.Y - centery)/D, z0 = 0.0f;
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auto y0 = (y2 * (A * z0 + G) - B * z0 - F) / (A + B * y2);
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auto x0 = x2 * (A * z0 - B * y0 + G);
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return {x0, y0, z0};
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}
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vector2i proj::xform_to_2d(const vector3& vec)
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{
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float projCoef;
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auto projVec = matrix_vector_multiply(matrix, vec);
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if (projVec.Z == 0.0f)
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projCoef = 999999.88f;
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else
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projCoef = d_ / projVec.Z;
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return
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{
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static_cast<int>(projVec.X * projCoef + centerx),
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static_cast<int>(projVec.Y * projCoef + centery)
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};
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}
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void proj::recenter(float centerX, float centerY)
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{
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centerx = centerX;
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centery = centerY;
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}
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