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COLLADA Bind Shape Matrices, should I store them or just bake the vertices


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#1 pondwater   Members   -  Reputation: 191

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Posted 19 June 2012 - 09:19 PM

I have a program that reads in Collada files and converts them into a nice runtime format.

For those familiar with the COLLADA format, should I store the Bind Shape Matrices, are they used for skinning/animation or in anyway needed? Or can i just bake the respective vertices in my format converter.

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#2 Ashaman73   Crossbones+   -  Reputation: 6960

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Posted 20 June 2012 - 01:42 AM

I have a program that reads in Collada files and converts them into a nice runtime format.

For those familiar with the COLLADA format, should I store the Bind Shape Matrices, are they used for skinning/animation or in anyway needed? Or can i just bake the respective vertices in my format converter.

Don't bake them and leave them as they are. The bind shape matrices are the connection between skin and skeleton, therefore you can use a single skeleton and its animation with several skins (and different bind shape matrices).

#3 turch   Members   -  Reputation: 590

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Posted 20 June 2012 - 08:37 AM


I have a program that reads in Collada files and converts them into a nice runtime format.

For those familiar with the COLLADA format, should I store the Bind Shape Matrices, are they used for skinning/animation or in anyway needed? Or can i just bake the respective vertices in my format converter.

Don't bake them and leave them as they are. The bind shape matrices are the connection between skin and skeleton, therefore you can use a single skeleton and its animation with several skins (and different bind shape matrices).


During conversion, couldn't you attach the skin to the skeleton in the bind pose, move the skeleton back into a zero pose, and then bake the vertices in the position they are in?

#4 pondwater   Members   -  Reputation: 191

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Posted 20 June 2012 - 09:14 AM

I want to make sure we are refering to the same thing. In my question Bind Shape Matrix != Bind Pose Matrix.

The Bind Shape Matrices (BSM) im talking about seem to contain the affine transformation of the 'mesh object' (not an actual term). My static model files that do not contain joints have a BSM, for each mesh object.

For example, if in my single model file i have two meshes, a sphere centred on the origin and then a cube that is placed 2 units above the sphere, The BSM for the sphere will be a 4x4 identity matrix, while the BSM for the cube will be the identity matrix with [0,2,0,1] as the 4th column. The vertices of the cube must be transformed by the BSM to get their proper values.

Therefore, should I just bake these in the conversion process?

Sorry if im making you repeat yourselves.

#5 turch   Members   -  Reputation: 590

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Posted 21 June 2012 - 08:59 AM

Ah I see what you mean. I would bake those.




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