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matrices

Started by Freaker13 May 7, 2004 at 8:38 AM 2 replies 650+ views

Original Post

May 7, 2004 at 8:38 AM

Hi all, i alway's used dx matrices but now i implemented my own. i can rorate ,scale and translate but when i first move my object and then rotate it it seems it moves like this - = object

------------ 
|           |   
|     -     | 
|           |
|------------


------------ 
|           |   
|   \       | 
|           |
|------------


------------ 
|           |   
|   /       | 
|           |
|------------


------------ 
|           |   
|     -     | 
|           |
|------------

------------ 
|           |   
|       \   | 
|           |
|------------
------------ 
|           |   
|       /   | 
|           |
|------------
[\code]
it it turns around his own axis and around the world origin
the order of my transformations is(the same as i used with dx)
world = scale*rotation
world = world*translation

thx in advance

   



[edited by - freaker13 on May 7, 2004 9:40:21 AM]

Prozak

May 7, 2004 at 8:54 AM

Make sure that your matrix code is fully DX-compliant, in other words, check to see if DX''s matrices are row-major or column-major, and be sure yours follow the same type.

Also, instead of aplying a whole sequence of transformations to your model, aply just one, and see if the end result matches. Try to see if the problem arises from rotation and/or translation.

Create 2 similar functions, one that renders with DX alone, and another that does the transformation using your matrix class, see how much they are diferent.

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szinkopa

May 7, 2004 at 11:50 AM

I think rotation is normally performed about an axis, which goes through the origin.
So you first have to scale, then rotate, and finally translate an object.

Freaker13

May 7, 2004 at 5:36 PM

its my rotation matrix that's wrong
dx matrix:


0.976588	0	0.215116	
0		1	0	
-0.215116	0	0.976588

my matrix:


0.976588	0	0.215116
0		1	0
0		0	0.976588

whats my fault? i use this algo to get the rotation matrix:


float A = (float) cos(eulerAngleX);
float B = (float) sin(eulerAngleX);
float C = (float) cos(eulerAngleY);
float D = (float) sin(eulerAngleY);
float E = (float) cos(eulerAngleZ);
float F = (float) sin(eulerAngleZ);
float AD =(float) A * D;
float BD =(float) B * D;

matrix[0][0]  =   C * E;
matrix[0][1]  =  -C * F;
matrix[0][2]  =   D;

matrix[1][0]  =  BD * E + A * F;
matrix[1][1]  = -BD * F + A * E;
matrix[1][2]  =  -B * C;

matrix[2][0]  = -AD * E + B * F;
matrix[2][1]  =  AD * F + B * E;
matrix[2][2] =   A * C;

[edited by - freaker13 on May 7, 2004 6:38:31 PM]

[edited by - freaker13 on May 7, 2004 6:39:21 PM]

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