skydave
Hi,
Does anybody know what the packing means for the attribute data section? Seems the packing is specified as an uniform array where for 4 component vectors means that packing is xyz xyz … w w. I wonder how packing would look like for xyzwxyzw. Does anybody know it exactly?
I would guess xyzwxyzw packing would be
and xxxyyyzzzwww would be but I am not sure…
The “packing” and “pagesize” fields are only used for interpreting how data is packed in the “rawpagedata” array. The pages are sequential in the “rawpagedata” array, and each page is packed as per the “packing field”.
Suppose you have 4 elements with values .., and your page size is 2, for a simple example.
A packing of means that
“rawpagedata”,[
X0, Y0, Z0, X1, Y1, Z1, W0, W1 # page 0 (subvector0, subvector1)
X2, Y2, Z2, X3, Y3, Z3, W2, W3 # page 1 (subvector0, subvector1)
]
A packing of means that
“rawpagedata”,[
X0, Y0, Z0, W0, X1, Y1, Z1, W1 # page 0 (subvector0)
X2, Y2, Z2, Z3, X3, Y3, Z3, W3 # page 1 (subvector0)
]
A packing of means that
“rawpagedata”,[
X0, X1, Y0, Y1, Z0, Z1, W0, W1 # page 0 (subvector0, subvector1, subvector2, subvector3)
X2, X3, Y2, Y3, Z2, Z3, W2, W3 # page 1 (subvector0, subvector1, subvector2, subvector3)
]
Worth noting is that packing is optional, and if missing, means that the same as would.
Finally, we internally also support a “constantpageflags”, which is just an array of boolean arrays, with one boolean array for each subvector, with each value indicating whether that page is constant.
For example, with a packing of , and X0=X1, Y0=Y1 and Z0=Z1, we could have
“constantpageflags”,[,]
“rawpagedata”,[
X0, Y0, Z0, W0, W1 # page 0 (subvector0, subvector1)
X2, Y2, Z2, X3, Y3, Z3, W2, W3 # page 1 (subvector0, subvector1)
]
You probably don't need to worry to much about this last. Houdini won't use the “constantpageflags” by default, though one could save geometry files with it using the HDK.
