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Matrix modify seperately

Started by nullmind Jan 17, 2004 at 3:19 AM 1 reply 1.1k views

Original Post

Jan 17, 2004 at 3:19 AM

Ok, I have a matrix. I''m using D3DX, because I don''t want to code my own again :o The matrix is rotated, scaled and translated at any time, so it can be anything. I want to simply set either rotation, scaling or translation, independent of the others. Say I modify the matrix, then I want to make the rotation 0.0f,0.0f,0.0f. But not resetting the Translation or Scaling. Is it possible? My first guess was to get the rotation, and multiply the matrix opposite of that. Any ideas? Cheers!

Dreamforger

Jan 17, 2004 at 8:27 AM

I''d rather store all the parameters of the matrix seperately and only update the matrix if needed. this of course assumes you don''t allow direct write access to the matrix itself, but only through the functions.

Something like this:


class Matrix
{
private:
  ScaleType scl;
  RotationType rot;
  TranslationsType trans;

  int isDirty;

  CalcMatrix(); // does your maultiplications and sets isDirty to 0

  float m[4][4];
public:
  Matrix(){isDirty = 1; }

  const float **Access(){ if (isDirty) CalcMatrix(); return m; }
  void Set...(...); // write Methods for all scl, rot, and trans members
}

This code probably is not without errors but I trust you get the idea. A nice way to substitute the Access method would be some operator overloading.

nullmind

Author

nullmind

Jan 17, 2004 at 8:44 AM

Well, I suppose that works fine.

Also, without starting another thread. Does anyone have any tips on ''moving'' an object? Not translating it, but moving it base on it''s rotation.

Cheeers, and thanks for the feedback.

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