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Author Topic: Best quality on heavy project  (Read 4199 times)

VHZN

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Best quality on heavy project
« on: October 19, 2018, 03:50:18 PM »
Hi everyone.

I've been working on a heavy project: a district modelisation.

Here is the first step i currently have:



Now, my config is:

Ryzen 7 2700x
GTX 1080
32Gb RAM

Currently for the project i have 650 photos (aligned). Each photo is 20Mpix.

No prob for aligning photos, because for 1 000 i need 5GB.

I've tried building in Height-field mode, but i lose too much detail on house front.

So i go for Arbitrary mode, but, i don't have enough ram to make it (500 photos= 15 GB - 45 GB for medium).

Do you have any idea i can do to get the max of my config and make it with the higher detail possible ?

Many thanks.

VHZN

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Re: Best quality on heavy project
« Reply #1 on: October 20, 2018, 01:08:57 PM »
So i'm actually trying to build the mesh in Arbitrary Mode.

Agisoft ram recommandation for building Mesh is (i have 700 camera aligned):

Low (500 cameras): 4GB - 12GB
Medium (500 cameras): 15GB - 45GB

So it crashed in medium, but it's ok since i don't have enough ram (32GB)

But in low it crashed too (1 000 000 face count).
I've tried at 300 000 face count and it still crash.

Pretty sure Agisoft crash because of my ram being too low. But i don't understand why ? Maybe the fact tha my camera are 20 Mpix ?

I would like to stay in Arbitrary because in need the vertical texture too.

Any idea to help me fix this issue ?



VHZN

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Re: Best quality on heavy project
« Reply #2 on: October 20, 2018, 02:18:47 PM »
Here i have the project with Mesh -> Height field -> High

And texture -> Orthophoto / Mosaic / Texture size: 8192


Limpopo_River

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Re: Best quality on heavy project
« Reply #3 on: October 20, 2018, 05:43:53 PM »
VHZN,

I think the problem with building the mesh in Arbitrary mode is that for any resolution you select (high, medium, or low), this step requires the same amount of RAM (as you said, up to 45 Gb for 500 cameras).  This is because Photoscan builds the mesh based on the density of the point cloud, then it decimates the mesh to the desired resolution setting you choose.  Reducing the resolution of the mesh after you've built the point cloud doesn't use any less RAM. 

I believe you have at least three choices:  1) split the model into chunks; 2) reduce the bounding box; or 3) reduce the density of the point cloud before building the mesh. 

Since you've already aligned the photos, I'd suggest trying option 2) by copying the point cloud 2x or more, and reducing the bounding box in each copy, so you have two or more slightly overlapping bounding boxes in separate copies of the point cloud.  Then process the mesh for each of the bounding boxes separately.  This is akin to processing the model in separate chunks but wouldn't require you to realign the photos for each chunk.  A possible variant of this method would be to select or turn off photos in different regions of the model in each copy of the point cloud to reduce the amount of data being processed into the mesh, but I haven't tried this.  Either way, you'd still need to process the mesh for each region from separate copies of the point cloud, and then merge them using Merge Chunks and selecting "Merge models."

Option 1, splitting the model into chunks, is less desirable because you'll need to realign the photos for each chunk, then align the chunks, and build the mesh for each chunk.  This often results in slight discontinuities between the chunks that are difficult to align perfectly. 

Option 3, reducing the density of the point cloud, would result in a model with lower resolution, but it might allow you to process it in a single chunk, avoiding the pitfalls of option 1.  Often, you don't need the highest density of the point cloud to get a model with acceptable resolution.  For this option, try re-aligning the photos at medium or high, instead of the highest accuracy.  Each lower setting in the alignment step will decrease the resolution of the model by a factor of 4.

Maybe others have better suggestions.  Let us know what method you choose and what works the best for you.

VHZN

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Re: Best quality on heavy project
« Reply #4 on: October 20, 2018, 06:44:45 PM »
First, thank you for your answer.

During my research i've found other persons in the same problem trying your Option 1. I didn't know i could do it (neither for the two other option) looks like there is script to do it. I'm gonna take a look.

I don't mind having to realign photos. So i'm ok going for the solution with the better result even if it take more time.
You say that Photoscan can "merge" separate chunks ? And when doing so, he will merge different model in the same one ?
What i fear about those technic is the merging phase. Does Agisoft handle it fine ?

My main objective for my model, is having the best texture quality, i don't really care about the maximal number of face count, or little detail in 3D (for exemple, i don't mind having house's windows on the same plan as the wall, even if in reality they aren't).

I've managed building the 3D Model (Height field -> High) and change the texture settings to Generic / Mosaic. It look better than my first try.

Last try right, first try left:



I'm currently building Tiled Model. Maybe the result will be better. Next i will try your option, and keep you updated !

I couldn't build a planar orthomosaic, not enough ram. I suppose i will have to build one orthomosaic by chunks / model, then align them with photoshop.

PS: Sorry for my english, i know it's a pain to read. But thank you for helping.

Limpopo_River

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Re: Best quality on heavy project
« Reply #5 on: October 20, 2018, 08:51:56 PM »
Hi VHZN,

It looks like your last version has much improved texture by processing it as a height field with generic/mosaic texture.  Given your parameters that time and model resolution aren't a major worry, I think Option 3, realigning the photos at the next lower quality setting (high, medium, or low), would also be a good choice.  This has the advantage that you could still process the model as an arbitrary mesh or as a height field before building the texture.  Anyway, since it appears you're getting good enough texture results with the current model processed as a height field, then there's probably no need to go back to Option 3 and realign the photos.

Whenever building a large model, I try to avoid splitting it into chunks to avoid problems with stair-steps or other discontinuities in the model.  To answer your question about aligning and merging chunks, Photoscan will merge the chunks into a single model but I've seen enough alignment problems with this approach to suggest it doesn't work as well as one might hope.

Best of luck

VHZN

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Re: Best quality on heavy project
« Reply #6 on: October 21, 2018, 12:36:25 PM »
Hi, and thank you for the answer.

To start here are the result of my new test:

Tiled model on the right, and model 3D with texture on the left (you have to scroll down my post to see the second screenshot):



Tiled model seems less accurate than texture model.

I've upload my model on Sketchfab so you could take a look.

(there is some music, you can mute it if you prefer)

To resume:
  • Tie Points 438,771
  • Dense Cloud 64,987,688 Medium
  • 3D Model 250 000 faces - Height Field - Dense cloud
  • Texture - Generic - Mosaic

I'm still not satisfied with the overall quality of the texture. I would like something more realistic, so i'm gonna start over and try other option. Option 3 to begin with, i would like to avoid having to merge separate model.

So, considering what you told me, here is what i'm gonna try:

-Realigning photo in low quality. If i understoof right, i'm gonna launch 3D model and Texture with higher settings if i use low quality on aligning. SO maybe in Arbitrary Mod, which should give me the best results.
-Building Dense Cloud with low quality again
-Building Mesh: Arbitrary - Dense Cloud - And a low face count (face count doesn't interess me, i want high texture resolution instead) - Pray my computer to handle it.
-Build Texture: Generic - Mosaic - 8192x1

IF, my computer can't handle Building Mesh with Arbitrary, then i would go with Height Fields...

« Last Edit: October 21, 2018, 12:43:10 PM by VHZN »