Texture Coords Translation

Graphics and GPU Programming Programming

Started by thekiwimaddog March 16, 2010 06:48 AM

10 comments, last by Evil Steve 14 years, 1 month ago

155

Author

March 16, 2010 06:48 AM

Hi Everyone! I'm trying change the texture coords on an object and I'm having trouble doing this using D3DXMatrixTranslation() with the code below:



m_d3dDevice->SetTextureStageState( 0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2 );

D3DXMATRIX matTrans;
D3DXMatrixIdentity(&matTrans);
D3DXMatrixTranslation(&matTrans,66.6f,66.6f,0.0f);

m_d3dDevice->SetTransform( D3DTS_TEXTURE0, &matTrans );

Test.Render();

However, the following code works fine:


m_d3dDevice->SetTextureStageState( 0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2 );

D3DXMATRIX matTrans;
D3DXMatrixIdentity(&matTrans);

matTrans._31 = 66.6f;
matTrans._32 = 66.6f;

m_d3dDevice->SetTransform( D3DTS_TEXTURE0, &matTrans );

Does anyone have any ideas why D3DXMatrixTranslation() is not working?? Any help would be greatly appreciated! Many Thanks David

thekiwimaddog

155

Author

March 16, 2010 11:25 AM

I'm still having touble with this. However, it's very strange as both D3DXMatrixRotationZ() and D3DXMatrixScaling() work fine.
Any Ideas Anyone?
David

Evil Steve

2,021

March 16, 2010 11:29 AM

Both bits of code should produce the exact same result. Have you tried comparing the generated matrices to see what the difference is?

thekiwimaddog

155

Author

March 16, 2010 12:52 PM

Thanks for the reply Evil Steve!
It's Messing up for some reason as you can see:
D3DXMatrixTranslation(&matTrans,66.6f,66.6f,0.0f);
1.0 0.0 0.0 0.0
0.0 1.0 0.0 0.0
0.0 0.0 1.0 0.0
66.6 66.6 0.0 1.0

What It Should Be:
1.0 0.0 0.0 0.0
0.0 1.0 0.0 0.0
66.6 66.6 1.0 0.0
0.0 0.0 0.0 1.0

Any Ideas Why Anyone??
Thanks
David

kauna

2,925

March 16, 2010 03:29 PM

Hi,

The D3DXMatrixTranslation routine is working with 4x4 matrices where the translation is stored in different elements, as you have already noticed.

The texture coordinate transform function expects you to provide a 4x4 matrix where only the 3x3 part is used.

Hope you understand.

Best regards!

For reference the d3dmatrix structure which d3dxmatrix inherits:

typedef struct _D3DMATRIX {    union {        struct {            float        _11, _12, _13, _14;            float        _21, _22, _23, _24;            float        _31, _32, _33, _34;            float        _41, _42, _43, _44;        };        float m[4][4];    };} D3DMATRIX;

JohnnyCode

1,084

March 16, 2010 03:52 PM

any vector you want to transform with a translation matrix must be passed to transform function in [x,y,z,1.0] 4 dimensional vector thus you get

1*x + 0*y + 0*z + 1*66.6f=translatedvec.x;

0*x + 1*y + 0*z + 1*66.6f=translatedvec.y;

0*x + 0*y + 1*z + 1*66.6f=translatedvec.z;

the translation part of matrix is stored as a 4th column allways (row in dx case).
the 1-3*1-3 portion of matrix is for rotation component.

In case you transform direction vectors(normalized vectors) not position vectors,
you do not use [vector,1.0] but [vector,0.0] input vector.

thekiwimaddog

155

Author

March 16, 2010 04:30 PM

You guys are going over my head here. :) What exactly do I need to do to get the matrix in a format that can be translated using the normal function?

Thanks Guys!
David

kauna

2,925

March 17, 2010 01:49 AM

Hi,

sorry for being too hard to understand.

What I meant to say that you cannot use D3DXMatrixTranslation in this case since it will place the translation in the elements matTrans._41,matTrans._42,matTrans._43.

The texture transformation matrix must have the translation in the elements matTrans._31,matTrans._32.

I hope you understand.

Best regards!

Evil Steve

2,021

March 17, 2010 03:44 AM

Quote:Original post by kauna
The texture coordinate transform function expects you to provide a 4x4 matrix where only the 3x3 part is used.

Really? Where does it say that? I can only find a reference to "Direct3D devices can transform the texture coordinates for vertices by applying a 4x4 matrix."

In any case - this is another reason to use vertex shaders; you have full control over what size of matrix you pass in [wink]

kauna

2,925

March 17, 2010 04:14 AM

Quote:Original post by Evil Steve
Really? Where does it say that? I can only find a reference to "Direct3D devices can transform the texture coordinates for vertices by applying a 4x4 matrix."

Another thread on this matter and here is an example of applying texture translation on Direct3d mobile.

I also suggest using the vertex shaders instead of fixed function pipeline.

Regards!

Texture Coords Translation

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