Demonstrating Cross or Dot Product?

[yznah]

this is a math node. so you can use it anywhere your rig or your shaders need maths stuff
for example i often need dot product operation in the rig to compute if 2 vectors are parallel or not

[BPorter]

Can you please elaborate? Why would two things need to be parallel? What are they?

I watched Bidirectional Constraining from Autodesk and they briefly discussed cross and dot product, but didn't go into any examples.

[yznah]

a basic one: you may need to activate a shape when a vector approaches another one (a limb that rotate to a certain position) it's the principle of poseDeformer i think

[zhenpanda]

a basic one: you may need to activate a shape when a vector approaches another one (a limb that rotate to a certain position) it's the principle of poseDeformer i think

so i looked up cross product in maya help and i got this example



float $v1[3] = {1,2,3};
float $v2[3] = {4,5,6};
crossProduct($v1, $v2, 0, 0);
// Results: -3 6 -3 //

so why is the results
-3 6 -3

and

vector $u=<<1,2,-2>>, $v=<<3,0,1>>; $w=cross($u, $v); // Result: <<2, -7, -6>> //

what is the math that's behind the cross product, and what does the result mean?

[yznah]

http://en.wikipedia.org/wiki/Cross_product
you can use cross product to compute normals of any plane
useful for orient joints :)

[zhenpanda]

http://en.wikipedia.org/wiki/Cross_product
you can use cross product to compute normals of any plane
useful for orient joints :)

I was reading the wiki page....
I'm bad at math...I still don't understand it....

[BPorter]

yznah - Maybe you can put a scene together to demonstrate how to use cross and dot product. I'm sure that will help us understand a little better. Thanks

[mlefevre]

Adam Mechtley demonstrates the cross product with his tutorial on Maya's aim constraints.

http://www.vimeo.com/2538054

Good stuff.. :) ..

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