cpp-game-engine/graphics/src/matrix.cxx

//
//  matrix.cxx
//  graphics
//
//  Created by Sam Jaffe on 5/24/19.
//  Copyright © 2019 Sam Jaffe. All rights reserved.
//

#include "matrix.hpp"

#include "game/math/angle.hpp"
#include "matrix/matrix.hpp"

namespace graphics {
  math::matr4 orthogonal_view(float left, float right, float bottom, float top,
                              float near, float far) {
    math::matr4 matrix;
    matrix(0, 0) = 2.f / (right - left);
    matrix(1, 1) = 2.f / (top - bottom);
    matrix(2, 2) = -2.f / (far - near);
    matrix(0, 3) = -(right + left) / (right - left);
    matrix(1, 3) = -(top + bottom) / (top - bottom);
    matrix(2, 3) = -(far + near) / (far - near);
    matrix(3, 3) = 1.f;
    return matrix;
  }

  math::matr4 frustum_view(float left, float right, float bottom, float top,
                           float near, float far) {
    math::matr4 matrix;
    matrix(0, 0) = 2.f * near / (right - left);
    matrix(1, 1) = 2.f * near / (top - bottom);
    matrix(2, 0) = (right + left) / (right - left);
    matrix(2, 1) = (top + bottom) / (top - bottom);
    matrix(2, 2) = -(far + near) / (far - near);
    matrix(2, 3) = -1.f;
    matrix(3, 2) = -(2.f * far * near) / (far - near);
    matrix(3, 3) = 0.f;
    return matrix;
  }

  math::matr4 perspective(math::degree fovY, float aspect, float front,
                          float back) {
    float tangent = tan(fovY);
    float height = front * tangent;
    float width = height * aspect;

    return frustum_view(-width, width, -height, height, front, back);
  }
}