moving objects in d3d...

This is a discussion on moving objects in d3d... within the Game Programming forums, part of the General Programming Boards category; i don't seem to be getting much help w/ this on the gamedev boards so i'm going to post it ...

  1. #1
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    Unhappy moving objects in d3d...

    i don't seem to be getting much help w/ this on the gamedev boards so i'm going to post it here:

    i'm trying to get objects within a 3d room i've created to move, but i can't seem to get it to work. the object class i'm writing initializes 4 vertices ( a square object ) and the square's x,y, and z world coordinates. here is the world transformation function:

    void MakeWorldMatrixStripObject4(D3DXMATRIX *pMatWorld, stripObject4 &pObject)
    {
    D3DXMATRIX MatZ,MatX,MatY,MatTemp;
    D3DXMATRIX MatRot;

    D3DXMatrixIdentity(&MatRot);

    D3DXMatrixRotationZ(&MatTemp, pObject.zRot);
    D3DXMatrixMultiply(&MatRot, &MatRot, &MatTemp);

    D3DXMatrixRotationX(&MatTemp, pObject.xRot);
    D3DXMatrixMultiply(&MatRot, &MatRot, &MatTemp);

    D3DXMatrixRotationY(&MatTemp, pObject.yRot);
    D3DXMatrixMultiply(&MatRot, &MatRot, &MatTemp);

    D3DXMatrixTranslation(pMatWorld,
    pObject.xPosWorld,
    pObject.yPosWorld,
    pObject.zPosWorld);

    D3DXMatrixMultiply(pMatWorld, &MatTemp, pMatWorld);
    }

    and i do this where i want to move the object:

    theSquare->xPosWorld += 1.0f;

    this only causes the entire world to move, however. what am i doing wrong? ... does each vertice need it's own world space coordinates? thanks to anyone that can help.

  2. #2
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    D3DXMatrix MatRot;
    D3DXMatrixIdentity(&MatRot);

    D3DXMatrixRotationZ(&MatTemp, pObject.zRot);
    D3DXMatrixMultiply(&MatRot, &MatRot, &MatTemp);
    This wastes time, just do this :
    Code:
    D3DXMatrixRotationZ(&MatRot,pObject.zRot);
    .
    .
    .
    Generally, the code's too slow since it creates a matrix for each axis rotation. You should write a function that creates a rotation matrix directly (without calling D3DX) ( I have one, I'll post it later, cause I don't quite have it right now).

    Anyway,
    this only causes the entire world to move, however. what am i doing wrong?
    You possibly did the following :
    1 - You set this rotation matrix as a world matrix
    2 - Render your object
    3 - Render the rest of the world (with the same matrix set)

    which is wrong, If you did this, change it to the following :
    1 - Set this rotation matrix as a world matrix
    2 - Render your object
    3 - Set the world matrix as an identity matrix
    4 - Render the rest of the world.

    The world matrix you created is specifically created for the object supplied, if you keep it set, it's going to rotate all the other objects too (and thus your world will get moved/rotated)
    Muhammad Haggag

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