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Hip file attached. how to cut a geometry/grid using a line/curve? I've tried polycut but it doesn't have a second input for the curve. cut geometry using curves.hiplc

I've tried: if(find(s@name,"rock")==1) @group_rock=1; but the number of primitives in the groups is 0, while there are a lot. Basically there are a lot of primitives, some have the word "rock" in the @name attribute, others don't I just need to isolate the ones with "rock" in the name. Should I be using a different function?

I attach a new hip file to show the problem. [instance_v2.hiplc] is the original but with file nodes which matches the kind of imported input. [instance_v2 method not working.hiplc] is where I apply the method you've given with a for each connected piece, but but it doesn't work. There are usually a lot more individual pieces than 3 or 4. These are only for demonstration purposes, easily hundreds per combo in reality. instance_v2.hiplc combo1.bgeo.sc combo2.bgeo.sc shape2.bgeo.sc shape1.bgeo.sc instance_v2 method not working.hiplc

Thank you. I've tried to use "Each Connected Piece" instead of chasing each piece separately with transform and attribute promote, but it doesn't seem to work. I get a file imported that has a lot more pieces as input, without their individual transform nodes, too many to work on each manually. Any advise?

I attach the hipfile. Here is what I've done: starting from an exact orientation for each shape (only 2), I turned each into a point and tried to render as instances instead of having the duplicate geometry, but I loose the orientation when I instance to the points. I do not want to have random orientation. It MUST be the exact same place, the exact same scape, the exact same orientation as the original. Is it possible? instance.hiplc

Alembic vs bgeo.sc which is more efficient, faster to work with inside Houdini? If I use an Alembic animation as an input for a simulation, will the simulation be faster if I first convert the alembic to bgeo.sc?

I have some primitive attributes on a geometry. When I save as bgeo.sc (ROP Geometry Output), the attributes remain when imported, when I save as obj, they're gone. Is there a way I can save obj with primitive attributes?

Rookie question in lighting: Do I have to make sure the pixel values don't go beyond 1 when the light is very bright to avoid clipping? Is there a case where the pixel value may go beyond 1? Below is a human body on which a very bright sun is shining, I had to increase it's exposure so I can get brighter global illumination, but I ended up with clipping.

it says in the docs: "Scatter channel to read from the volume object. This acts as a multiplier on the scatter color, to texture the color of the volume." https://docs.arnoldrenderer.com/display/A5AFMUG/Standard+Volume What multiplication is that? 1 (colour white) * density? There is a big mess in the bottom of the cloud so I'd like to know what is the formula used? what's multiplied by what? If my volume is 9 times denser and the colour is 1 (white), does it mean the denser the brighter? I've included comparison (top: empty channel, bottom: channel is density)

I have attached files. I just can't get any self-shadows on volume. I've rendered the shadow matte testing on a polygonal geometry and it works like a charm, but for the volume (in this case a cloud) I can't get anything at all, using both: - just shadow matte AOV - duplicated volume with shadow matte material Everything works fine for polygons, nothing whatsoever works for volumes when it comes to shadow matte / pass. Am I doing something wrong? I need the self shadows of the volume. The volume (cloud) is from Disney: https://www.disneyanimation.com/data-sets/?drawer=/resources/clouds/ And here are the houdini hip files shadow_matte_polygonal_geometry_works.hiplcshadow_matte_polygonal_geometry_works.hiplc floating.bgeo.sc shadow_matte_volume_does_not_work.hiplc shadow_matte_polygonal_geometry_works.hiplc

Does Arnold now support packed primitives in scattering or do I have to use the old instancing method?

The Disney Cloud dataset includes multiple resolution versions with the highest being almost 1,5 billion voxels (2.8 GB file size). Does this stuff get used like this, with so many voxels? Here is the link: https://disneyanimation.com/resources/clouds/ Can someone shed some light on the resolution range for cloud in production (close up, mid, background)?

I attach the hipfile of a closed interior scene, just a window letting the light in. I have a VERY HARD TIME lighting the REST of the scene, the one that's not close to the window is unrealistically dark. Am I doing something wrong? I've tried with: Dome light HDRI + Sun Exposure 10 + Portal 1, exposure 22! + Portal 2, exposure 21! + Area light exposure 8 The light doesn't go further, the rest of the scene is dark and the window area is too bright. If I add a point light inside to cheat, I get the bright spots on the ceiling, the floor and nearby walls/objects. If I add an area light the rear will be darker than the front, if I make it double sided, the edges will be darker. Here is the free scene I'm using (file sop): https://www.turbosquid.com/3d-models/3d-design-kitchen-gray-model-1616267 Perhaps, a more direct question: how would you light it? lighting_interior.hiplc

For an old scene, I'm switching to Arnold, how do I add the Arnold tab in the parameters window? is there something like the "Add OBJ Parameters" in Redshift menu:

Thanks a lot for the prompt reply. I will check it. Perhaps I've formulated in a confusing way, let me try it again in 4 words: HDRI or Plain colour?