hw1

总的来说,hw1是比较简单的. 本次作业的任务是填写一个旋转矩阵和一个透视投影矩阵,只要记得上课时候给的公式,写进去就行.

• 旋转矩阵 注意,cos,sin等,需要的参数为弧度制(rad),而不是角度制

Eigen::Matrix4f get_model_matrix(float rotation_angle) {
  Eigen::Matrix4f model = Eigen::Matrix4f::Identity();
 
  // TODO: Implement this function
  // Create the model matrix for rotating the triangle around the Z axis.
  // Then return it.
  rotation_angle = rotation_angle / 180 * MY_PI;
  Eigen::Matrix4f rotate;
  rotate << cos(rotation_angle), -sin(rotation_angle), 0, 0,
      sin(rotation_angle), cos(rotation_angle), 0, 0, 0, 0, 1, 0, 0, 0, 0, 1;
  model = rotate * model;
  return model;
}

先进行挤压,再进行正交投影得到结果

• persp2ortho

  • 透视投影到正交投影的变化矩阵

• ortho

  • 正交矩阵 projection = ortho * persp2ortho * projection;

Eigen::Matrix4f get_projection_matrix(float eye_fov,
                                      float aspect_ratio,
                                      float zNear,
                                      float zFar) {
  // Students will implement this function
 
  Eigen::Matrix4f projection = Eigen::Matrix4f::Identity();
 
  // TODO: Implement this function
  // Create the projection matrix for the given parameters.
  // Then return it.
  Eigen::Matrix4f persp2ortho = Eigen::Matrix4f::Identity();
  Eigen::Matrix4f ortho = Eigen::Matrix4f::Identity();
 
  float top = abs(zNear) * tan(eye_fov / 2 / 180 * MY_PI);
  float bottom = -top;
  float right = top * aspect_ratio;
  float left = -right;
 
  persp2ortho << zNear, 0, 0, 0, 0, zNear, 0, 0, 0, 0, zNear + zFar,
      -zNear * zFar, 0, 0, 1, 0;
 
  ortho << 2 / (right - left), 0, 0, -(right + left) / (right - left), 0,
      2 / (top - bottom), 0, -(top + bottom) / (top - bottom), 0, 0,
      2 / (zNear - zFar), -(zNear + zFar) / (zNear - zFar), 0, 0, 0, 1;
 
  projection = ortho * persp2ortho * projection;
  return projection;
}

最后得到的结果与官方答案不同,图形倒转了.这是zNear值导致的. 根据课上的内容,看向的是Z轴负半轴,Z<0; 而代码中,看向Z正半轴,Z>0;

小问题懒得修改了.

顺便学习了一下cmake的相关知识 cmake