[Bf-python] 3DVec * 4x4Matrix issue

[Gilbert, Joseph T.]

I believe it's not physically converted to 4d, only coerced to 4d for
the purposes of multiplication.

-----Original Message-----
From: bf-python-bounces at projects.blender.org
[mailto:bf-python-bounces at projects.blender.org] On Behalf Of Campbell
Barton
Sent: Monday, July 24, 2006 5:31 AM
Cc: Blender Foundation Python list
Subject: Re: [Bf-python] 3DVec * 4x4Matrix issue

Just tried and assign vec.w=1  to a 3d matrix dosent work.
Aside from that, converting to a 4d vec isnt ideal because it wont work 
for wrapped vecs.

Would changing the functionality to be like this be acceptable ( in C 
though )

mtx= ob.matrixWorld
vec= vec*mtx
vec= vec+mtx.translationPart()


So no resizing, just apply the tx.


Gilbert, Joseph T. wrote:
> KK. I remember that someone else complained about this along time ago
> that you had to call resize4D() on a 3d vector everytime you wanted to
> multiply vs. a transformation matrix. This is annoying and
unnecessary.
> So there was a commit applied that allowed a implied resize of 3d
> vectors (just adding a 1 to w position I think) when multiplying vs.
4D
> matrices.
>
> -----Original Message-----
> From: bf-python-bounces at projects.blender.org
> [mailto:bf-python-bounces at projects.blender.org] On Behalf Of Campbell
> Barton
> Sent: Monday, July 24, 2006 4:53 AM
> Cc: Blender Foundation Python list
> Subject: Re: [Bf-python] 3DVec * 4x4Matrix issue
>
> perhaps the change got revoked or dosent work for some reason, bucause

> at the moment its not doing that
> Ill take a look at this when I do the other Mathutils stuff.
>
> Gilbert, Joseph T. wrote:
>   
>> As I remember I applied a fix where 3d vectors would act as 4d
vectors
>> when multiplying vs. a 4D matrix. There may be something in the code
>>     
> to
>   
>> this respect.
>>
>> -----Original Message-----
>> From: bf-python-bounces at projects.blender.org
>> [mailto:bf-python-bounces at projects.blender.org] On Behalf Of Campbell
>> Barton
>> Sent: Friday, July 21, 2006 11:19 PM
>> To: Blender Foundation Python list
>> Subject: [Bf-python] 3DVec * 4x4Matrix issue
>>
>> Hi, This was mentioned a while ago, but I dont think any conclusion
>>     
> was 
>   
>> reached..
>>
>> A problem I come across almost weekly from new scripters is how to
get
>>     
>
>   
>> the worldspace location of a vector from object data, a vert say 
>> (through emails end blenderartist python forum)
>>
>> world_vec= vec*matrix works if the vector  4D but for 3D vectors it 
>> dosent apply the translation.
>>
>> Solutions are ...
>>
>> mtx= ob.matrixWorld
>> vec_copy= Mathutils.Vector(vec)
>> vec_copy.resize4D()
>> vec=vec_copy*mtx
>> vec.resize3D()
>> or...
>>
>> mtx= ob.matrixWorld
>> vec=vec*mtx
>> vec= vec+mtx.translationPart()
>> or..
>>
>> do the matrix multiplication manually..
>>
>> Could we just have the matrix multiplication apply transformation to
a
>>     
>
>   
>> 3D vector?
>>
>> - Cam
>>
>> _______________________________________________
>> Bf-python mailing list
>> Bf-python at projects.blender.org
>> http://projects.blender.org/mailman/listinfo/bf-python
>>
>>   
>>     
>
>
>   


-- 
Campbell J Barton

133 Hope Street
Geelong West, Victoria 3218 Australia

URL:    http://www.metavr.com
e-mail: cbarton at metavr.com
phone: AU (03) 5229 0241
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