Maya Particle Disk Cache (PDC) Utils :
PDC Utils help in creating PDC files of external data. These file can then be used to drive particle system in Maya. It contains 2 programs one to create pdc files and another to read them. Both are command line only utility.
Writepdc program creates a pdc file using ascii input files
Readpdc program can read pdc files and display their content on the terminal window
Both programs are compatible with Maya 6 and 7 PDC format. No testing done for prior versions
Download: Source code and executible bundle (89 kb)Updated March 13th 2006
Tutorial: As time permits there would be a tutorial available showing how to put together things. Below are some clues to glue things together
Hints:
- Create a particle system in maya (Dynamics menuset)
- Save scene and set the project directory (Very Imporant)
- Solvers -> Create Particle Disk Cache
- Solvers -> Disable Memory Cache
- Save scene (Important)
- Browse to the project folder and then to particles/yourSceneName folder
- There should be *.#.pdc files in increments of 200 or 250 or something like that
- Now you just need to create your own pdc files using the writepdc tool above with same filename (They should match exactly) and replace/overwrite the one's that maya created.
- You should be able to see the changes in Maya instantaneously
Source Code Credits: Amit Chourasia (San Diego Supercomputer Center) and Peter J. Lu (Harward University) and generous help from John Moreland at SDSC.
Maya PDC format Simplified |
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| The PDC file is used by Maya's particle disk caching and startup cache. It is a binary file that holds one frame's worth of data for a single particle object. The unit for PDC files is always cm |
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Row no |
Content |
Byte Count |
Description |
Default |
Extra Info |
Example |
Example Explanation |
Row no |
| 1 |
PDC file header
|
4
|
Characters indicating that this is a PDC file. This will be the 4 characters "P", "D", "C", " ". |
"P", "D", "C"," "
|
last one is space character (no commas or quotes)
|
"P", "D", "C", " "
|
Compulsory. No changes should be made here. | 1 |
| 2 |
4
|
One Integer indicating the file format version number.
|
1
|
Avoid changing this untill you know for certain. No documentation about it.
|
1
|
Lets stick to default | 2 | |
| 3 |
4
|
One Integer holding bit information about whether the values stored in the file are BIG_ENDIAN or LITTLE_ENDIAN.
|
1
|
Maya only likes Big_Endian. So always use 1. |
1
|
Always use 1 for this | 3 | |
| 4 |
8
|
2 Integers holding extra bit information that various file format version might decide to use.
|
0, 0
|
Avoid changing these. No documentation about them |
0 0 |
Lets stick to default | 4 | |
| 5 |
4
|
1 Integer indicating the number of particles represented in this file |
"N"
|
N is the no of particle you need
|
5
|
Lets say our particle system contains 5 particles | 5 | |
| 6 |
4
|
1 Integer indicating the number of attributes that have values stored in this file. |
" M "
|
M is the no of attributes you'll write in the file (eg position, particleID, rgbpp,etc) |
1
|
We'll just write 1 attribute for position on per particle basis. | 6 | |
|
Header size
|
28 Bytes
|
28 Bytes
|
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There will be "M" records ie record for each attribute. Each record will consists of the following |
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| 7 |
Single Record
(There will be M records like this) |
4
|
Integer indicating the length of the attribute's name =L where L is the length of the name. |
8
|
8 (no of characters in string "postion") | 7 | ||
| 8 |
L
|
L Characters indicating the name of the attribute |
position
|
position | 8 | |||
| 9 |
4
|
1 Integer indicating the type of data for the current attribute. Choose the number from the following data type map below (Row no10) |
Per Object Attributes are set for all particles so they are single numbers. (ie of type 0,2,4 ) See row 10 Per Particle attributes are set for each particle so naturally they are an array of the data. (ie of type 1,3,5 ) See row 10 |
5
|
As position is specified as 3 doubles ie a vector and we have to specify this on per particle basis our datatype becomes 5 (vector array). See the info below on choosing data type.(Row No10) |
9 | ||
| 10 |
P
|
Data Type 0 ---> Integer 1 ---> Integer Array 2 ---> Double 3 ---> Double Array 4 ---> Vector 5 ---> Vector Array |
0 ---> Integer (just one int=4 bytes - usually per object attribute) 1 ---> Integer Array ( N ints=N*4bytes - where N is the number of particles, usually per particle attribute) 2 ---> Double (just one double=8bytes - usually per object attribute) 3 ---> Double Array ( N doubles=N*8bytes - where N is the number of particles, usually per particle attribute) 4 ---> Vector (3 doubles=3*8bytes - usually per object attribute) 5 ---> Vector Array ( N vectors=N*3 doubles=N*3*8bytes - where N is the number of particles, usually per particle attribute) |
1.0 1.0 1.0
2.0 2.0 2.0 3.0 3.0 3.0 4.0 4.0 4.0 5.0 5.0 5.0 |
x, y, z corrdinates for each particle. Maya stores floating points in double precision using 8 bytes. | 10 | ||
|
Single Record Size
(The record size for each attribute will vary according to data type) |
8+L+(N*B) Bytes |
N * B Bytes representing the data for this attribute, where L is the no of characters in attribute name N is the number of particles or 1 for non-array data B is the number of bytes needed to represent the data type. |
N*B= 5*(3*8)=120
8+L+N*B=8+8+120 =136 Bytes |
x y z are 3 doubles occuring 5 times | ||||
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Total File Size
(Summation of header and M record size) |
28+size of M record Bytes |
28 bytes of header M records of size (8 + L + B) (8 + L + B) is going to be different for each attribute |
28 + 1*(136)=148
Bytes |
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Reference: Maya Documentation
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Caution: Since format contains data that is not word aligned there could be potential problems with different compilers. In a loose words what it means is when you read data from memory by providing a memory address or pointer you might get incorrect results. As compilers will hand you the data from a valid address rather than from where you asked from. Our implementation takes care of this. |
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