Projection Matrix

Orthographic Projection

template <typename T>
 GLM_FUNC_QUALIFIER tmat4x4<T, defaultp> ortho
 (
  T left,
  T right,
  T bottom,
  T top,
  T zNear,
  T zFar
 )
 {
  tmat4x4<T, defaultp> Result(1);
  Result[0][0] = static_cast<T>(2) / (right - left);
  Result[1][1] = static_cast<T>(2) / (top - bottom);
  Result[2][2] = - static_cast<T>(2) / (zFar - zNear);
  Result[3][0] = - (right + left) / (right - left);
  Result[3][1] = - (top + bottom) / (top - bottom);
  Result[3][2] = - (zFar + zNear) / (zFar - zNear);
  return Result;
 }

Perspective Projection

 template <typename T>
 GLM_FUNC_QUALIFIER tmat4x4<T, defaultp> frustum
 (
  T left,
  T right,
  T bottom,
  T top,
  T nearVal,
  T farVal
 )
 {
  tmat4x4<T, defaultp> Result(0);
  Result[0][0] = (static_cast<T>(2) * nearVal) / (right - left);
  Result[1][1] = (static_cast<T>(2) * nearVal) / (top - bottom);
  Result[2][0] = (right + left) / (right - left);
  Result[2][1] = (top + bottom) / (top - bottom);
  Result[2][2] = -(farVal + nearVal) / (farVal - nearVal);
  Result[2][3] = static_cast<T>(-1);
  Result[3][2] = -(static_cast<T>(2) * farVal * nearVal) / (farVal - nearVal);
  return Result;
 }

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