Forums Technical Discussion Reading and writing ramps and ramp properties

Reading and writing ramps and ramp properties

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andrewlowell
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A two part technical question:

1). I'm trying to read a ramp in it's entirety. Meaning, loop through all the parameters in the node, hit the ramp .. and gather the ramp (which is a parmTemplate in hou), but also all of the keys, positions, interpolation switches. Right now I can certainly loop through all parms or tuples, but hitting a technical wall when it comes to getting what I'd probably see when I go to edit parameter interface, I want at those. So how would I do that in Python?

2). Next, I'd like to save all relevant information about a ramp into an attribute. This is quite a bit more complicated than say a float parameter. In which I'm already taking the name of the parm, making that the attribute name, then assigning the float value. A ramp could be reproduced as a list, a string, or what I'm seeing in VOPs/VEX as a struct. But there doesn't seem to be a good way to pipe that into an attribute.

Has anyone ventured into i/o with ramps? I'd really like to read, compact, and reuse them as attributes.
Edited by andrewlowell - Oct. 18, 2020 22:00:05
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Enivob
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Have you played around with what the .asCode() method kicks out? What if you just wrote that to disk? Then you could execute the python code to re-establish the ramp later..?

Here is the code that will generate one TAB on a ramp. (it's actually made up of three parameters.)
# Code for /obj/geo1/attribwrangle1/shape1pos parm 
if locals().get("hou_node") is None:
    hou_node = hou.node("/obj/geo1/attribwrangle1")
hou_parm = hou_node.parm("shape1pos")
hou_parm.lock(False)
hou_parm.deleteAllKeyframes()
hou_parm.set(0)
hou_parm.setAutoscope(False)


# Code for /obj/geo1/attribwrangle1/shape1value parm 
if locals().get("hou_node") is None:
    hou_node = hou.node("/obj/geo1/attribwrangle1")
hou_parm = hou_node.parm("shape1value")
hou_parm.lock(False)
hou_parm.deleteAllKeyframes()
hou_parm.set(0)
hou_parm.setAutoscope(False)


# Code for /obj/geo1/attribwrangle1/shape1interp parm 
if locals().get("hou_node") is None:
    hou_node = hou.node("/obj/geo1/attribwrangle1")
hou_parm = hou_node.parm("shape1interp")
hou_parm.lock(False)
hou_parm.deleteAllKeyframes()
hou_parm.set("linear")
hou_parm.setAutoscope(False)
Edited by Enivob - Oct. 19, 2020 09:20:19
Using Houdini Indie 20.0
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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andrewlowell
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Thanks Enivob, this is quite a bit more granular than I'm looking for however. The first step is actually finding all the parameters that a the macro-ramp parm contains. Right now they just all seem to be unique parms, which is true. But I just can't believe there isn't a .getchildparms() type thing for a ramp parm. Going by name just seems so sloppy.

I think I might need to write my own format for these things if it doesn't exist, this would need to be stored in an attribute and then read and reconstructed in vops/vex.

I haven't tried the ascode, but this would need to be a non-moving parts thing. No setting of parms or reading writing. Basically:

loop through all parms on a node
if ramp, get all parms in ramp
record all values in reconstruct-able way in point attribute
use point attribute to reconstruct ramp and process data in vops/vex
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andrewlowell
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Here's a complete workflow which:
1. Reads node parameters, including ramps.
2. Turns them into point attributes
3. Uses them downstream

Attachments:
point_cloud_reader_dev.v01.hip (198.0 KB)

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papsphilip
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Enivob
Have you played around with what the .asCode() method kicks out? What if you just wrote that to disk? Then you could execute the python code to re-establish the ramp later..?

i am trying to find out how this works and implement it in a python module. Can you share a working example of this for a ramp parameter because i am testing the one they have in houdini documentation and its not working for me so far. i dont see the python file in my hip directory where it should be according to the open function documentation
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