Author Topic: Errors only when rendering at a large size  (Read 418 times)

Offline daudvyd

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Errors only when rendering at a large size
« on: September 11, 2018, 05:07:51 PM »
Hi folks, the attached image renders fine at 640x480. However, Terragen immediately shows thousands of errors at 6400x4800. Also, at the higher image size, Terragen switches to only use 30% of CPU instead of 100% of CPU. In both the small size and the large size, I'm using cropping to focus on just the upper right quarter of a larger image. Can anyone explain what this particular error means and why it is showing just at the larger size?

Online WASasquatch

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Re: Errors only when rendering at a large size
« Reply #1 on: September 11, 2018, 05:12:39 PM »
Seems like the ray tracer can't handle that resolution with what's going on in your scene. The rather extreme displacement and exploded terrain may be the culprit.

Also when you crop, TG will dynamically scale to what it actually needs to spend time on, so you may not see the full CPU usage. I'm doing a crop right now of a pond and only seeing about 20% usage on the last little bit it's rendering.

Offline daudvyd

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Re: Errors only when rendering at a large size
« Reply #2 on: September 11, 2018, 05:56:11 PM »
Thanks for the diagnosis. Are there any level of detail or other settings for the raytracer that I could tweak to render the scene at higher resolution? It is failing to render the part I like the most!

Online WASasquatch

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Re: Errors only when rendering at a large size
« Reply #3 on: September 11, 2018, 05:58:26 PM »
Thanks for the diagnosis. Are there any level of detail or other settings for the raytracer that I could tweak to render the scene at higher resolution? It is failing to render the part I like the most!

Perhaps you could try raising the patch size on your Compute Terrain, though this may change the look of the terrain a bit. In general the displacement is really strong, and will be a long render if it does let you in high res.
« Last Edit: September 11, 2018, 07:57:23 PM by WASasquatch »

Offline Matt

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Re: Errors only when rendering at a large size
« Reply #4 on: September 11, 2018, 11:58:38 PM »
Generally this shouldn't happen, so there is a bug here. Would it be possible to send us a TGD? If you can simplify it in some way and still reproduce the error, that would be even better.
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Offline daudvyd

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Re: Errors only when rendering at a large size
« Reply #5 on: September 12, 2018, 05:51:04 AM »
Hi Matt. I'm happy to send the TGD to you folks if it would help in debugging. Please provide a Terragen email address.

Offline Matt

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Re: Errors only when rendering at a large size
« Reply #6 on: September 12, 2018, 06:19:50 AM »
Please send it to support@planetside.co.uk
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Offline Oshyan

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Re: Errors only when rendering at a large size
« Reply #7 on: September 13, 2018, 01:56:29 AM »
Also when you crop, TG will dynamically scale to what it actually needs to spend time on, so you may not see the full CPU usage. I'm doing a crop right now of a pond and only seeing about 20% usage on the last little bit it's rendering.

I'm not sure what you've said makes sense or is accurate. In cropping, as many resources as possible are used, just like a regular render, but they are dedicated to the crop area. As far as CPU usage is concerned it shouldn't inherently affect it. It's possible that a small enough crop region combined with certain bucket settings/limitations might mean fewer buckets are created than there are threads available, especially in a high-core-count CPU. But that would really be a "perfect storm" type of situation.

What happens toward the end of some renders is that some render buckets can take longer to complete than others, and since Terragen does not have dynamic bucket subdivision, only the originally assigned CPU thread will be working on that last bucket. This is when CPU usage can drop notably. But it has nothing to do with crop rendering.

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Online WASasquatch

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Re: Errors only when rendering at a large size
« Reply #8 on: September 13, 2018, 04:33:25 AM »
Also when you crop, TG will dynamically scale to what it actually needs to spend time on, so you may not see the full CPU usage. I'm doing a crop right now of a pond and only seeing about 20% usage on the last little bit it's rendering.

I'm not sure what you've said makes sense or is accurate. In cropping, as many resources as possible are used, just like a regular render, but they are dedicated to the crop area. As far as CPU usage is concerned it shouldn't inherently affect it. It's possible that a small enough crop region combined with certain bucket settings/limitations might mean fewer buckets are created than there are threads available, especially in a high-core-count CPU. But that would really be a "perfect storm" type of situation.

What happens toward the end of some renders is that some render buckets can take longer to complete than others, and since Terragen does not have dynamic bucket subdivision, only the originally assigned CPU thread will be working on that last bucket. This is when CPU usage can drop notably. But it has nothing to do with crop rendering.

- Oshyan

Perhaps it's because I have such a limited resolution there is just so much I can't adequately test. But from my end, there's always noticeable CPU usage differences between a crop and a full render. And I have 4 threads. Lol And that 84% quickly dropped to 75% while there were still those four tiles. Additionally, a full render achieves more rendering quicker by rendering consequentially in a row (spread out over those 4 threads/tiles) compared to columns with some crops.

Offline ajcgi

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Re: Errors only when rendering at a large size
« Reply #9 on: September 13, 2018, 10:20:53 AM »
WASasquatch - do you think that could be to do with virtual cores vs physical ones? It's something I've noticed in other apps before.

Online WASasquatch

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Re: Errors only when rendering at a large size
« Reply #10 on: September 14, 2018, 02:45:20 AM »
WASasquatch - do you think that could be to do with virtual cores vs physical ones? It's something I've noticed in other apps before.

I am not sure, as I only have a low-end CPU so I just have 4 core and 4 threads, none virtual that I am aware of.

 

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