Trip Report Point Loma Whale (180 fsw)

[beldridg]

We've been doing a lot of exploratory dives with @California Diver and @DiveTucson on the Marissa with Lora and Chris recently but had a whopper of a find on our second dive yesterday.

We had been looking for airplanes (another post on that coming soon) and Lora had noticed a blip on the sonar between dives so we went back to investigate the next day. Imagine our surprise when Ben and I got down and found a completely intact whale skeleton. Crazy indeed.

We are now in touch with NOAA and Scripps to potentially dive it again to get more data.

The story along with links to the photogrammetry model and photos are posted here:

Lora’s Point Loma Whalefall (Point Loma — 180 fsw)

Here are some screen captures of the photogrammetry model:

 

[DiveTucson]

Super fun few days on the water! Can honestly say this was the first time I have ever dove a dead whale.

 

[Johnoly]

In photogrammetry,,,How do you "eliminate?" the ever present schools of fish in the model so just the structure is remaining?

Fantastic whale capture in perfect condition considering how the ocean swells can destroy and flatten even huge steel ships .

 

[stronj1]

Wow, amazing!

 

[Ulfhedinn]

Well that is pretty incredible. The photos on your site are pretty cool too.

 

[beldridg]

In photogrammetry,,,How do you "eliminate?" the ever present schools of fish in the model so just the structure is remaining?

Fantastic whale capture in perfect condition considering how the ocean swells can destroy and flatten even huge steel ships .

I don't know if I have a perfect answer on your question about fish, but I have some thoughts.

There are a few different steps when building a photogrammetry model. The first is that the software needs to "align" the photos which it does through detecting possible connection points and then correlating them. This is _definitely_ an area where fish can be problematic. Metashape has the ability to "mask" parts of the picture so that it doesn't use those to detect points for alignment but, at least for me, it is pretty time consuming.

The next stage is building a dense cloud and then building the mesh and then building the texture.

I'm guessing that your question is primarily related to the last process and what is generally the "end state" of the models that you see. In this case, the software has a few different options on how to build the texture but it generally uses a combination of all the photos that cover the same area that it is building the texture for. So, if you have 4 photos that all have some overlap on that area, it will use some kind of combination (I'm not sure exactly how it does that).

Now, to answer your question: My _belief_ is that since the fish are generally moving, they would likely be in only one of the pictures and would hence not get put into the final texture.

HOWEVER, I have had situations where fish doesn't move and is in enough pictures to get included in a model. For example, on one of my early models of a section of the UB88 sub, there is a wolf eel in the starboard side bow torpedo tubes. Below is a link to the model and a screenshot.

I hope that helps.

UB88 Starboard Side Torpedo Tubes - Download Free 3D model by Brett Eldridge (@beldridg) [69e3b4e]

 

[beldridg]

Well that is pretty incredible. The photos on your site are pretty cool too.

Thanks! I hope you are getting some good diving in at Laguna Beach and San Diego!

- brett

 

[Ulfhedinn]

Every chance I get

 

[San Diego Climber]

Certainly a departure from the planes and boats that are usually on your blog! Photogrammetry is so fascinating. Couple of questions:

1. How long does it take start-to-finish (at least for the whale carcass)- from when you get the photos on your machine to when the model is ready, assuming you're not taking breaks?
2. What's the longest runtime step rendering-wise?
3. Are you using the standard or pro version of Metashape?
4. What are the hardware specs on the machine you're rendering on?

 

[beldridg]

Certainly a departure from the planes and boats that are usually on your blog! Photogrammetry is so fascinating. Couple of questions:

1. How long does it take start-to-finish (at least for the whale carcass)- from when you get the photos on your machine to when the model is ready, assuming you're not taking breaks?
2. What's the longest runtime step rendering-wise?
3. Are you using the standard or pro version of Metashape?
4. What are the hardware specs on the machine you're rendering on?

Hi, the blog post below should answer most of your questions. I'm currently using Metashape Standard (I can't justify the cost of Pro for a hobby).

Photogrammetry Technical Details & Equipment

The processing time is very highly dependent upon the quality of the model you want to build. For example, a typical model might take 1-2 hours start-to-finish on "Medium" quality settings on my computer but take 5-6 hours on "High" or "Ultra High" settings.

I hope that helps.

- brett