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Attrib create

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Im trying to understand the use of attributes in Houdini.


I have a shattered and fractured wall, that should / should not be broken when the ball hits it.

To accomplish that I have made a point sop with $BBY set in both x,y and z (add color), a vopsop where I have created a ramp from color to color on the output so that I can have ramp controll over what is black and what is white on my wall.

I have then created an attribcreate, and set the name to "strenght", and set the value to "if ($CR < 0.2, -1, $CR * 100000)". I can now see that the strength of the glue is controlled by the ramp. If the color is below 0.2 the strength will be set to -1 and it will not break. Perfect.


But, why? How does Houdini understand that this value will affect the glue?? Is it because I have written "strength" in the name of the attribcreate? And if... why?

Im having a hard time understand everything that has to do with the attribcreate. If I have created this strenght attribute with my attrib create node, how is it then possible that Houdini already knows what the strength should refer to. And if Houdini already know what I mean about strength, why do I then need to make strength with the attrib create node?


Please help me understand this.









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Ok, so why do I need to "create an attribute" with the "attrib create"-node if the strength is already an attribute?

And how can I know that strenght already is an attribute and that the strength is tied to glue strength?

Thanks for explaining to me.



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reading help may help



as it says:"If a primitive attribute with the same name as a constraint property (such as damping) is present, the attribute value will be multiplied with the value from the constraint sub-data."


so because Glue Constraint DOP has Property called strength it can be modulated by creating strength attribute on your constraint links

to clarify, strength attribute doesn't exist by default and it doesn't have to exist at all for glue constraint network to work, but if you create it (by any way, Attrib Create, VOPs, Wrangles, ...) it will be used to multiply Strength Property/Parameter of the Glue Constraint per link otherwise the value of Strength Property would be used for all links

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