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Author Topic: Transforming Vertices issue  (Read 1153 times)

Cristero

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Transforming Vertices issue
« on: February 10, 2015, 09:52:33 AM »
Hi. I searched the forum for the known problem of the huge amount of time Vray takes to "transform vertices", but didn't find anything suitable for my scene.
I have a simple scene at the moment, with a HDRI and 8 different kinds of plants and grass clumps that need to be scattered.
I've tried with proxies and without them and the result is always the same: 4 or 5 minutes just to transform vertices, even if I'm using low Vray settings.
The models of grass are from the archmodels 124 collection, so they are quite detailed. I can't attach the scene here because it is too large, but if you know any other way just let me know.
I have a dual Xeon machine with 56 thread. Do I have to set the threads manually into the general rollout of the forest object?
Anyway, I attach a screenshot with the distribution map and the forest stats.
Thanks in advance.

iToo

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Re: Transforming Vertices issue
« Reply #1 on: February 10, 2015, 11:09:03 AM »
Hi, although Forest computes the distribution of items in the "transform vertices" stage, this rendering phase is used also for other Max processes, so it's difficult to know what is causing the slowdoness.

The number of threads used by Forest is automatic, but you can override it using General->CPU threads. Please, try using a lower value (< 10) and check if there is some difference.

Also according to the screenshot, your Forest object scatters more than 1.7 mill. of items. But this value is estimated, the real number of items may be greater.
I've attached a test scene with 4 mill. of teapots. Please, render it and check what is the "transform vertices" time for your computer.
Carlos Quintero
iToo Software

Cristero

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Re: Transforming Vertices issue
« Reply #2 on: February 10, 2015, 11:20:08 AM »
Hi, although Forest computes the distribution of items in the "transform vertices" stage, this rendering phase is used also for other Max processes, so it's difficult to know what is causing the slowdoness.

The number of threads used by Forest is automatic, but you can override it using General->CPU threads. Please, try using a lower value (< 10) and check if there is some difference.

Also according to the screenshot, your Forest object scatters more than 1.7 mill. of items. But this value is estimated, the real number of items may be greater.
I've attached a test scene with 4 mill. of teapots. Please, render it and check what is the "transform vertices" time for your computer.

9 seconds to transform vertices and 16 to compile geometry.
Could the slowdoness be caused by the fact that my grass objects are scattered along the normals of a quite large high poly surfaces (200k polygons)?

iToo

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Re: Transforming Vertices issue
« Reply #3 on: February 10, 2015, 01:36:51 PM »
9 seconds to transform vertices and 16 to compile geometry.
Could the slowdoness be caused by the fact that my grass objects are scattered along the normals of a quite large high poly surfaces (200k polygons)?

No, the surface should have not a significative impact on performance.
In this case, i would suggest to create a test scene from the original file, and simplify it progressively (replace objects by teapots, override materials, etc.) until isolate the problem.

If you send us the scene to support@itoosot.com (please use WeTransfer for large files), we may take a look to it.
Carlos Quintero
iToo Software

Cristero

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Re: Transforming Vertices issue
« Reply #4 on: February 10, 2015, 02:11:02 PM »
9 seconds to transform vertices and 16 to compile geometry.
Could the slowdoness be caused by the fact that my grass objects are scattered along the normals of a quite large high poly surfaces (200k polygons)?

No, the surface should have not a significative impact on performance.
In this case, i would suggest to create a test scene from the original file, and simplify it progressively (replace objects by teapots, override materials, etc.) until isolate the problem.

If you send us the scene to support@itoosot.com (please use WeTransfer for large files), we may take a look to it.

Ok, I'm uploading the scene through WeTransfer.
There's no texture along with the scene, so you can easily check if it's a map or material issue.

iToo

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Re: Transforming Vertices issue
« Reply #5 on: February 10, 2015, 07:02:31 PM »
Thanks for the scene. The main cause of slowdown is the Edge mode, combined with a huge number of items. Although Forest stats estimates 1.7 mill., the real value is more than 6 mill.
First of all, i suggest to use Point (which is the faster mode) instead Edge mode. Next, apply the usual methods to generate less items (as Camera clipping or Camera falloff). Also, if possible, decreasing the density a bit would help a lot.

Anyway, i just noticed that scattering time on these massive distributions, is faster on the first run but significatively worse on next iterations. This happens until Max is reset. We'll investigate that issue.
Carlos Quintero
iToo Software

Cristero

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Re: Transforming Vertices issue
« Reply #6 on: February 10, 2015, 07:17:44 PM »
Thank you so much.
I'll do as you suggest.
Greetings.