Hi guys, excelent toolkit, and this is my question: whats the minimum number of cameras necessary to record a .3dl file? I've seen two configurations, 9 cameras and 15 cameras, but i think that 4 cameras is the minimum, 3 around the actor and 1 over his head. Or maybe, i have to use 7 cameras, 6 around the actor (3 recording from his waist to his head, and 3 from his feet to his waist ) and 1 over his head. Am i wrong?
Thank you
Best regards
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Well, actually, you can get the result even with only two cameras, but the quality will be very bad. From our experience, you will need at least four cameras to get acceptable quality, 4 around the actor and 1 over his head. The more cameras you use, the better quality you will get.
Moreover, our rendering algorithm is a visual hull based algorithm. So, each camera must capture the whole object, otherwise, some parts of the captured object will not be displayed in the result. For more information on our algorithm, you can read our paper: 3D Live: Real Time Captured Content for Mixed Reality , in International Symposium on Mixed and Augmented Reality (ISMAR'02).
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Hi,
thank you for your answer, i've read 3D Live: Real Time Captured Content for Mixed Reality (it has been helpful) and when you say "....at least four cameras to get acceptable quality, 4 around the actor and 1 over his head......." i assume five (not four) cameras.
On the other hand, at the paper, the links between Image Processing Computers and Recording Computer are via gigabit Ethernet, and here is my new question: do i need more than a ieee 1394 link for this task? (i dont think so)
Thank you
Best regards
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I am sorry, in the last post, I wrote wrongly, it should be "...at least five cameras to get acceptable quality, 4 around the actor and 1 over his head...".
Regarding your second question, in our system, Image Processing Computers and Recording Computers are linked by Gigabit Ethernet Nework, not by IEEE 1394 links. All these computers are connected to a Gigabit Network Hub and share the same network LAN. We only use IEEE 1394 to connect our cameras to Image Processing Computers.
I hope this can answer your questions.
Qui Tran
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Thanks again for your answer, but i didn't the right question, it should be: if ieee 1394 bus between cameras and image processing computers is full used, then, is it good enough 400Mbps to link recording computers and image processing computers? I'm thinking about this because of information flow between image processing computers and recording computer is raw images, doesn't it?
Thank you again, and i'm sorry for so many questions
Best regards
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Actually, we need more than 400Mbps to link recording computers and image processing computers. Thats why we are using Gigabit network. The following will explain why we need more than 400Mbps.
The data flow between Image Processing Computers and Recording Computers is not raw images but images in Bayer format (only 1 byte for 1 pixel). For more information about this format, you can have a look at http://www.siliconimaging.com/RGB%20Bayer.htm. In our system, we capture images from 9 cameras at resolution 640 x 480 and at 30 frames per second. So, the amount of data sent through network every second is:
640 x 480 (pixels) x 1 (Byte/pixel) x 9 (cameras) x 30 (fps) ≈ 80 MBps = 640 Mbps.
So, we need at least 640Mbps link in order to reach 30 fps. If you use 400 Mbps, the maximum frame rate you can get is:
400 Mbps / (640 x 480 (pixels) x 1 (Byte/pixel) x 9 (cameras)) ≈ 19 fps.
Furthermore, it is very difficult to utilize the whole bandwidth. With Gigabit network (1Gbps), but normally we can only reach about 600Mbps. We are still investigating how to utilize the whole bandwidth of our network. Do you have any idea on this?
Qui Tran
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Hi guys, excelent toolkit, and this is my question: whats the minimum number of cameras necessary to record a .3dl file? I've seen two configurations, 9 cameras and 15 cameras, but i think that 4 cameras is the minimum, 3 around the actor and 1 over his head. Or maybe, i have to use 7 cameras, 6 around the actor (3 recording from his waist to his head, and 3 from his feet to his waist ) and 1 over his head. Am i wrong?
Thank you
Best regards
Hi,
Well, actually, you can get the result even with only two cameras, but the quality will be very bad. From our experience, you will need at least four cameras to get acceptable quality, 4 around the actor and 1 over his head. The more cameras you use, the better quality you will get.
Moreover, our rendering algorithm is a visual hull based algorithm. So, each camera must capture the whole object, otherwise, some parts of the captured object will not be displayed in the result. For more information on our algorithm, you can read our paper: 3D Live: Real Time Captured Content for Mixed Reality , in International Symposium on Mixed and Augmented Reality (ISMAR'02).
Hi,
thank you for your answer, i've read 3D Live: Real Time Captured Content for Mixed Reality (it has been helpful) and when you say "....at least four cameras to get acceptable quality, 4 around the actor and 1 over his head......." i assume five (not four) cameras.
On the other hand, at the paper, the links between Image Processing Computers and Recording Computer are via gigabit Ethernet, and here is my new question: do i need more than a ieee 1394 link for this task? (i dont think so)
Thank you
Best regards
Hi,
I am sorry, in the last post, I wrote wrongly, it should be "...at least five cameras to get acceptable quality, 4 around the actor and 1 over his head...".
Regarding your second question, in our system, Image Processing Computers and Recording Computers are linked by Gigabit Ethernet Nework, not by IEEE 1394 links. All these computers are connected to a Gigabit Network Hub and share the same network LAN. We only use IEEE 1394 to connect our cameras to Image Processing Computers.
I hope this can answer your questions.
Qui Tran
Thanks again for your answer, but i didn't the right question, it should be: if ieee 1394 bus between cameras and image processing computers is full used, then, is it good enough 400Mbps to link recording computers and image processing computers? I'm thinking about this because of information flow between image processing computers and recording computer is raw images, doesn't it?
Thank you again, and i'm sorry for so many questions
Best regards
Hi,
Actually, we need more than 400Mbps to link recording computers and image processing computers. Thats why we are using Gigabit network. The following will explain why we need more than 400Mbps.
The data flow between Image Processing Computers and Recording Computers is not raw images but images in Bayer format (only 1 byte for 1 pixel). For more information about this format, you can have a look at http://www.siliconimaging.com/RGB%20Bayer.htm. In our system, we capture images from 9 cameras at resolution 640 x 480 and at 30 frames per second. So, the amount of data sent through network every second is:
640 x 480 (pixels) x 1 (Byte/pixel) x 9 (cameras) x 30 (fps) ≈ 80 MBps = 640 Mbps.
So, we need at least 640Mbps link in order to reach 30 fps. If you use 400 Mbps, the maximum frame rate you can get is:
400 Mbps / (640 x 480 (pixels) x 1 (Byte/pixel) x 9 (cameras)) ≈ 19 fps.
Furthermore, it is very difficult to utilize the whole bandwidth. With Gigabit network (1Gbps), but normally we can only reach about 600Mbps. We are still investigating how to utilize the whole bandwidth of our network. Do you have any idea on this?
Qui Tran
Sorry, this website cannot display the approximate sign and in my post, these signs are automatically changed to "≈".
So, in this post, "≈" means "approximate".
Ok, thanks a lot, all your explanations were very helpful.
Greetings.