Byte Color Components versus Floats
The tele-immersion data sets are point-clouds where each point has XYZ and RGB information. Previously, each of component of XYZ and RGB have been floats.
However, since colors are eventually converted to 8-bit components, RGB could be 3*8 bits instead of 3*32 bits.
Below is a comparison of tele-immersion data with 7-bit* color components versus 32-bit floats. Basically it looks fine. The 7-bit file is 2,004,809 bytes, and the float file is 3,207,668 bytes, so the ration is about 5/8!
Future directions:
I'd assumed that OpenGL required float data for XYZ information,
but i just checked and GLVertex3s is a call for specifiying XYZ with 'GLShort' components, which i presume are 16-bit. If we're able to get that to work, the data would go from 64 bits per point to only 24 bPP, or a ratio of 3/8.
Current streaming speeds indicate a theoretical maximum frame rate of about 6Hz with 64bPP, so that maximum could go up to about 16Hz, which is much more appealing.
On the resolution of 16-bit spacial information:
16 bits has a resolution of one part in 65,000.
The tele-immersion "playpen" is approximately 10 feet in each dimension, which translates to a 16-bit resolution of about .002 inches, or about .05 millimeters, which is pretty good.
* For some reason, OpenGL via Croquet interprets byte color components as being in the range 0-127, not 0-255. Values over 127 are clamped to zero. See http://bugs.impara.de/view.php?id=1684.
edit: Bert Freudenberg has clued me in that GLBYTE is a signed value; i want GLUNSIGNEDBYTE or equivelant. Thanks Bert !
However, since colors are eventually converted to 8-bit components, RGB could be 3*8 bits instead of 3*32 bits.
Below is a comparison of tele-immersion data with 7-bit* color components versus 32-bit floats. Basically it looks fine. The 7-bit file is 2,004,809 bytes, and the float file is 3,207,668 bytes, so the ration is about 5/8!
Future directions:
I'd assumed that OpenGL required float data for XYZ information,
but i just checked and GLVertex3s is a call for specifiying XYZ with 'GLShort' components, which i presume are 16-bit. If we're able to get that to work, the data would go from 64 bits per point to only 24 bPP, or a ratio of 3/8.
Current streaming speeds indicate a theoretical maximum frame rate of about 6Hz with 64bPP, so that maximum could go up to about 16Hz, which is much more appealing.
On the resolution of 16-bit spacial information:
16 bits has a resolution of one part in 65,000.
The tele-immersion "playpen" is approximately 10 feet in each dimension, which translates to a 16-bit resolution of about .002 inches, or about .05 millimeters, which is pretty good.
* For some reason, OpenGL via Croquet interprets byte color components as being in the range 0-127, not 0-255. Values over 127 are clamped to zero. See http://bugs.impara.de/view.php?id=1684.
edit: Bert Freudenberg has clued me in that GLBYTE is a signed value; i want GLUNSIGNEDBYTE or equivelant. Thanks Bert !
posted by orion at 3:49 PM
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