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Author Topic: Alignment algorithm, does color matter?  (Read 4433 times)

Marcel

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Alignment algorithm, does color matter?
« on: July 06, 2014, 10:23:58 PM »
I am trying to scan an interior which has white plastered walls. The walls are too featureless to align well, so I'm thinking of adding some small pieces of painters tape on the wall (ripped into random shapes) to give Photoscan better features to extract.

My question is if the point matching is color sensitive, or if it operates on black and white. If it is color sensitive I can use several different colors tape for even more differentiation. (Even better would be a roll of tape printed with random shapes!)

David Cockey

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Re: Alignment algorithm, does color matter?
« Reply #1 on: July 06, 2014, 11:37:53 PM »
My recollection is that Rhino works on color, not just brightness.

I've never had success using pieces of tape to add texture. Let us know how it works for you.

chrisd

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Re: Alignment algorithm, does color matter?
« Reply #2 on: July 07, 2014, 07:18:27 AM »
There have been a few discussions here on noise projection ... might be useful for this.

Marcel

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Re: Alignment algorithm, does color matter?
« Reply #3 on: July 07, 2014, 09:40:15 AM »
There have been a few discussions here on noise projection ... might be useful for this.

The space is too big for noise projection I'm afraid, I would need several really strong flash guns.

Quote from: David Cockey
My recollection is that Rhino works on color, not just brightness.

I've never had success using pieces of tape to add texture. Let us know how it works for you.

I will try Post-it notes with a random ink blob (stamped with a ball of crumpled paper). It seems this pattern generates a good amount of points. The edges or corners of the notes don't generate any points at all, so I can see why you didn't have good results with just tape.


 (I will use yellow Post-its for more contrast)

Now the question is now many notes I need to put on my wall for a decent alignment.

I wish there was some paint that I could just splatter on and that disappears after a day. I know there exists wallpaper glue that is a light pink color when wet but completely transparent when dry.

James

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Re: Alignment algorithm, does color matter?
« Reply #4 on: July 07, 2014, 09:52:34 AM »
I think unless you have really close up high res pictures you might not get so many points on the post its in practice. How about using painters tape to stick up sheets of newspaper?

Marcel

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Re: Alignment algorithm, does color matter?
« Reply #5 on: July 07, 2014, 11:10:58 AM »
Yes, this was not such a good comparison, although if the blobs are smaller it'll still work I think.

Sheets of newspaper is a great idea, at has a perfect pattern and I don't have to spend time stamping :) Thanks!

Wishgranter

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Re: Alignment algorithm, does color matter?
« Reply #6 on: July 07, 2014, 01:35:38 PM »
Yes its better that the "pattern" is in color....... but its not mandatory. news paper is ideal. as its not UNIFORM pattern.... at least when the press write something usefull :-D
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