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Slow Viewport Sim. Quick Sim when entering specific frame

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Hi everyone!

I'm currently going through the Procedural Cities in Houdini Tutorial from Pluralsight.
So far everything worked out great. I had to adjust some nodes (As the tutorial was made in Houdini 15) But it's working. 

I'm now in the process of aligning bounding boxes of Buildings to the geometry surrounding them (e.g. rotating the buildings so they face the streets) Using a bulletsolver and popattract.
In the tutorial video this simulation runs smoothly... when I'm opening the exercise files on my Computer it runs fine too. But with my own file the viewport runs slow (like 1 frame every second) 
The perfomance monitor shows this: 

(The dopimport took even more time but I bypassed it here to see if the problem was somewhere else) 

I'm not sure where to check for the __DopDetailLook_Guide or how to influence it. 
But it seems to be viewpoert related, as entering a framenumber in the timeline simulates super quick and gives the right result... 

So this isn't really breaking anything as I can get the correct result anyways without waiting forever, still I would love to know why the simulation runs so poorly in the viewport. 

If anyone wants to see the hipnc file I'm happy to upload it somewhere. 

Any help would be greatly appreciated!


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It could be your hardware is different than the author of the tutorial. It's hard to say in a complex setup without taking a look at the file.

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Posted (edited)


I thought so too, but I tried the exercise files attached to the course and it simulated just fine. 
I rebuilt it with packed cubes and it worked too..and i have a lot more cubes than bounding boxes in the original version.. hm 

I attached the hip file if anyone wants to take a look. the problem is in the red box-> cityblocks_sim...
The input nodes there are frozen now...hope that removes the need to import the "buildings"..otherwise they are in the placeholderBuildings.zip.
The test setup with the cubes is also in the hip file. 




Edited by colorofblack

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Okay I seem to have found the culprit. 
The Buildings get packed after removing the ones not in the city block. In the pack node Create Packed Fragments is checked by default.
It is also active in the course...but deactivating it improves the simulation framerate drastically..not sure why... if anyone knows what it does and why you 
have to deactivate it I would be happy to konw 

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Hi Daniel, I had a quick peek at your file yesterday, you resampled the boxes to a very high detail. With a Resample SOP node. Then you packed them and sent to DOP. I don't think that it is necessary and it slows down the DOP a lot. You may check the tutorial, what is the purpose of their Resample (and then Fuse), and how it should be used.

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