Static points on deforming geometry

[rayt]

Hi,

I'm trying to scatter points onto a surface provided from maya and imported as alembic geometry. To get the result I need, I have to convert the outside geo into a curve and then use a polywire to outline the geometry. Afterwards I need to scatter points into the polywire. However using the rest at frame 1 and then attribute interpolating the points onto the surface I still get twitchy points. Is there another way to do this where the points are static and moving with the polywire? Is there something I missed. I am not using a rest node, I am simply freezing the points on frame one.

 

Thanks in advance.

[mawi]

33 minutes ago, rayt said:

Hi,

I'm trying to scatter points onto a surface provided from maya and imported as alembic geometry. To get the result I need, I have to convert the outside geo into a curve and then use a polywire to outline the geometry. Afterwards I need to scatter points into the polywire. However using the rest at frame 1 and then attribute interpolating the points onto the surface I still get twitchy points. Is there another way to do this where the points are static and moving with the polywire? Is there something I missed. I am not using a rest node, I am simply freezing the points on frame one.

 

Thanks in advance.

Can you explain " I have to convert the outside geo into a curve and then use a polywire to outline the geometry. " part or submit a simple .hip file?

[rayt]

I am not sure how to bake alembic geometry into a scene. Hopfully this can clarify. The object is a 2d animated surface, and I am removing the internal edges and leaving only the perimeter edges. I then create a polywire out of the perimeter edges, and then apply the scatter to the polywire.

If you know how I can bake alembic geometry into a scene please let me know and then I can provide a hip file.

[Sean-R]

Edit: I think if you lock the node it should keep it in the file, not 100% sure though

The unpack SOP should do the job, although I think it still gives it to you as 1 prim. You could try the convert SOP?

Edited May 12, 2016 by Sean-R

[anim]

don't lock the node, since it's animated, just attach alembic as well

but overall make sure your geometry is not changing topology over time and as well that polywire is producing stable result and not flipping due to upvector problems. Then the Attribute Interpolate should work

[acey195]

what you can do possibly, is in each point save the primitive it is attached to, along with that primitive's intrinsic UV Values,
using the XYZdist() function in VEX.

After the animation (if the amount of primitives/points/vertices remain the same during it)

you can reapply this position again using VEX, in particular: v@P = primuv(0,"P",<connectedPrim>,<connectedPrimIntrUVvalue>);

 

[old school]

Look at the help file for the Scatter SOP: 

http://www.sidefx.com/docs/houdini15.0/nodes/sop/scatter

The Tip section right at the top describes three different scenarios to scatter fixed point positions on deforming geometry including an example file. Very fast and you only evaluate the Scatter SOP from the frame you use in the Time Shift SOP.

Btw rarely do you want to lock operators to get a rest frame in an input deforming archive. Always use the Time Shift SOP and 9 times out of 10 you are setting it to frame 1 or the start frame of the sequence which is $FSTART (in case you are dealing with simulations that start at frame 1001 for example).

 

See the example file as to how to take in deforming unpacked geometry (from your alembic archive) and use an Ends SOP set to unroll then scatter and stick with the Attribute Transfer SOP using the recipe indicated in the help. See the attached example file for scattering on deforming edges.

stick_scatter_points_on_deforming_geometry.hip