[Sidefx-houdini-list] Get time from CH_Manager rather than OP_Context in HDK, why?

Pablo Giménez pablogipi at gmail.com
Fri Jul 29 12:44:49 EDT 2011

2011/7/28 Edward Lam <edward at sidefx.com>

> Hi Pablo,
> On 28/07/2011 1:33 PM, Pablo Giménez wrote:
>> BTW how can I get the current time using only CH_Manager, I am now
>> using: now = context.myTime + chman->getGlobalStart(); But I havent
>> seen any method in CH_Manager to get the same values as
>> context.myTime
> That is wrong. I think you're misinterpreting what those functions return.
> OP_Context::getTime() returns your the *absolute* time in seconds. Houdini
> generally deals with times as absolute values in seconds except in a few
> cases internal to CH_Channel/CH_Segment. So it is _incorrect_ to add
> OP_Context::getTime() to CH_Manager::getGlobalStart().
> The corresponding CH_Manager function to OP_Context::getTime() should be
> CH_Manager::getEvaluateTime(). Note however though that the caller is
> free to specify a different context time than the global time.
> Therefore, it is recommended to always use OP_Context::getTime()
> whenever possible.
> Note that CH_Manager's getGlobalStart()/getGlobalEnd(**) returns the
> values (in seconds, Houdini only deals with evaluation time values in
> seconds) corresponding to the frame range in Houdini's Global Animation
> options dialog.
>  Well more issues I have with frames and time. I am using all of this
>>  to set the start time of a particle system. Seems that no matter
>> what frame range you have, frame 1 is time 0.
> I understand how Houdini works with absolute time in seconds. This legacy
question is what confused me.

> This is due to legacy reasons.
>  What happens is that if you set start frame in a POP Network to be
>> 0, the sim begins on frame 1, even if your frame range is something
>> like [-10, 100].
> The POP network uses the global animation frame start (ie.
> CH_Manager::getGlobalStart()) to determine when to "reset". ie. where it
> will _not_ continue cooking from the previous state. When the POP
> network "resets", it will cook starting from the specified start time minus
> preroll.
> So if your global animation frame range is [-10, 100] while your POP
> network uses start time of 0 (frame 1), it will do the following:
>  - Reset at frame -10
>  - Do nothing until frame 1, at which time it starts cooking
> This situation can easily be tested with a simple POP network and a default
> Location POP.
All right I got it working now.
Thanks Edward!

> Best Regards,
> -Edward
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Un saludo
Best Regards
Pablo Giménez

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