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Rotations

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Hi! Lets say i created 2 cubes and render them to the screen , now how can i rotate around any axis just ONE cube , not the whole world (world tranformation) ??? tnx Xeno.

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In OpenGL you could use:

glRotatef(Amount to Rotate , X-Axis , Y-Axis , Z-Axis);

Call this function before the creation of the object you wish to rotate.


Edited by - reaptide on 4/19/00 3:15:44 PM

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If you''re using OpenGL, I''ve got the solution:
glMatrixMode(GL_MODELVIEW);
glLoadIdendity();
...
DrawCube();
glRotated(..);
DrawCube();

If you want to draw anything which shouldn''t rotate with the second cube, use glPushMatrix() before calling glRotate() and glPopMatrix() after drawing the rotated objects.

Visit our homepage: www.rarebyte.de.st

GA

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In Direct3D you have three matrices that control the final coordinates of the vertices.

The world matrix is used to place objects in the world coordinate system
The view matrix is used to transform world coordinates into camera coordinates
The projection matrix is used to project the view coordinates onto the screen

To rotate the cube you would do something like this:

D3DXMATRIX R, T, W;

D3DXMatrixRotationX(&R, Angle); // Rotate the cube around it''s own origin
D3DXMatrixTranslation(&T, Pos.x, Pos.y, Pos.p); // Translate it to its position in the world
D3DXMatrixMultiply(&W, &R, &T); // Concatenate the transformation matrices

pD3DDev->SetTransform(D3DTRANSFORMSTATE_WORLD, (D3DMATRIX*)&W);

Of course you can add more rotations, just keep in mind that the rotations should happen before the translation otherwise the cube won''t be where it''s supposed to be.



WitchLord

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You rotate the cube you want to rotate BEFORE you translate them.
Then you rot/trans them again for the world transformation.

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Hi,

Try using the D3D Util functions;

Set your objects position in the world..
D3DUtil_SetTranslateMatrix(position, xpos, ypos, zpos);

Here I''m rotating about x & y, so set up two rotation matrices..
D3DUtil_SetRotateYMatrix(yrotate, yangle);
D3DUtil_SetRotateXMatrix(xrotate, xangle);

Multiply them together to form one rotation matrix..
D3DMath_MatrixMultiply(rotate, yrotate, xrotate);

Now multiply the positional and rotational matrices into the player matrix..
D3DMath_MatrixMultiply(MatrixPlayer, position, rotate);

These Util functions can be a little long winded at times, but they are very robust and error-free (I hope!) so they are great when your starting out (like me :-) )

Remember to #include

Cheers

Matt



Check out my project at: www.btinternet.com/~Matthew.Bennett

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That include is d3dutil.h

There you go, you wait for a D3D answer and three come at once!

Cheers

Matt



Check out my project at: www.btinternet.com/~Matthew.Bennett

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Tnx a Lot guys u really helped me!
so tell me if i right:
lets say i want to render 2 cubes, and i want to rotate just one of them so:
1. render the first cube
2. rotate and transelate the world and all the things
3. render the second cube

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The process for render the scene should be something like this

1. Set the projection matrix
2. Set the view matrix
3. Set the world matrix
4. Render an object
5. If there are more objects go to step 3

Of course it is usually unnecessary to set the projection matrix and perhaps even the view matrix every frame.



WitchLord

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thanks a lot a lot alot!!!!!!
thats what i needed to know!!!

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