When I drop a SOP import DOP in a DOP network, its default parameters are full of stamps():



What is stamps(), exactly? The document [www.sidefx.com] says:

Returns a copy stamping string value.

...sorry, but what's a copy stamping? Why does SOP import DOP need it?

In SOPs there used to be Copy SOP, lafer renamed to Copy Stamp SOP and deprecated, which allowed you to define "stamping variables" which could vary values per each copy

stamp() function for floats and stamps() for string were a way to evaluate such variables of a specific node per each copy and therefore modify left side nodes for each copy

This was replaced by for loops due to several technical reasons


However stamp() and stamps() were and still are also used in DOPs in a similar fashion, to evaluate certain variable values during cook and therefore being able to change behavior of nodes like SOP Solver based on which object is currently running over etc.

More info here https://www.sidefx.com/docs/houdini/nodes/dop/sopsolver.html [www.sidefx.com]

tamte
In SOPs there used to be Copy SOP, lafer renamed to Copy Stamp SOP and deprecated, which allowed you to define "stamping variables" which could vary values per each copy

stamp() function for floats and stamps() for string were a way to evaluate such variables of a specific node per each copy and therefore modify left side nodes for each copy

This was replaced by for loops due to several technical reasons


However stamp() and stamps() were and still are also used in DOPs in a similar fashion, to evaluate certain variable values during cook and therefore being able to change behavior of nodes like SOP Solver based on which object is currently running over etc.

More info here https://www.sidefx.com/docs/houdini/nodes/dop/sopsolver.html [www.sidefx.com]

What confuses me is that I can middle click the parameter to show its value even it uses stamps(), just like other expressions. But if stamps() is evaluated during cook, does it mean the value we see by middle clicking it is not necessarily meaningful?

raincole
What confuses me is that I can middle click the parameter to show its value even it uses stamps(), just like other expressions. But if stamps() is evaluated during cook, does it mean the value we see by middle clicking it is not necessarily meaningful?

Correct, the value you see is the 3rd argument of stamp*() function, which defines a default value shown when evaluated out of context

Doesn't have to be meaningless, it's certainly a placeholder