Point() For Undefined Point

[rdg]

Hello,

I am not sure how to articulate my question, so please skip it if it's too uncoordinated.

I copy boxes onto a particle system.

I have a NULL with a spare channel animation.

I stamp the following expression onto the boxes sz:

cht("../null1/growth", point("../popnet1", $PT, "life", 0))

so far so good: the boxes scale after birth.

Now I plug a grid instead of the popnet into the second input of copy.

The popnet doesn't birth as much particles.

The boxes where PT exits for a grid point and a particle act like I expect.

For all others where no particle exists all scale like the last particle.

I would expect them not to scale at all as I cannot get a life for a particle that doesn't exist, do I?

Maybe a popnet returns always the last acessible particle and not undefined?

Thank you.

Georg

rdg_growth.6.hipnc

[doc]

That does seem strange a little strange.

I tried the same thing with just a grid and a point expression

/obj/model/grid2 -> echo `point(".",150,"P",0)`

The grid only has 100 points but when quering the position of a

point that's out of range it returns the value from the highest (in terms of point number) existing point.

might be a bug, might be by design.

Doesn't really matter just, add more points to your popnet

Luca

[stevenong]

Based on your hip file, you can use an AttribTransfer SOP to transfer "life" to the grid which will get you what you want.

I agree with doc that it seems strange. Bug or design? You decide.

Cheers!

steven

rdg_growth_attribtransfer.6.hipnc

[rdg]

Bug or design?

Luca & Steven,

thanks for your answers.

I'd vote for design as this behaviour is less error-prone.

Otherwise you would have to use try()catch() like stuff

if(point()!=undefined, point(), foo())

Thanks for remixing my hip.

It took me while to re-engineer it.

Why do you use the attribtransfer, you still need point() to get the life?

Georg

[stevenong]

The point expression in the Copy SOP now refers to the AttribTransfer SOP & not the point1 SOP connected to the POP Network. I hope I answer your question.

Cheers!

steven

[rdg]

If I get the attribute via attribute transfer it doesn't return values for undefined points.

That is a reason to use attributeTransfer.

I first thought attributetransfer would make the point() expression obsolete and provide $LIFE.

Thanks.

Georg