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Found 75 results

  1. I wasn't entirely sure what to call this as its quite a complex task.. Basically, lets say I have a faceted spehere with some boxes around it. I want to create a primitive attribute on my faceted sphere which corresponds to an id stored on each box and will essentially tell the shader which box it should render. So maybe 'attribute-based object linking' is more appropriate.. Is this possible? In my head I was thinking I could create a shader for the sphere and inside send a test ray to check what this interescts with, if the object id that it hits corresponds with the sheres primitive id that the ray came from then render this object, if not then ignore this object and carry on pathtracing... This would need to be done for reflection and refraction.. Possible?
  2. Hello! I have a question for what I thought would be fairly simple to figure out. I'm trying to use an attribute from a per point object level to influence the emission strength of my Arnold material. I'd usually just use a bind node, but that option isn't available in Arnold. Anyone know the HtoA equivalent? Thanks in advance for any tips.
  3. Access array attribute wrangle

    Hey, I have a bunch of points with 3 float attributes, b[0] b[1], b[2] If I want to access only the second attribute, specifically through a wrangle (for learning), how would I do this? I've tried @foo = point(@p,"b",1) but that only returns the first attribute value. Presumably because I'm not asking for an array? Thanks!
  4. I'm trying to get attributes from a volume and group them by whatever data type they are. I was able to get the float type attributes imported, but I'm having difficulties with the vector types. My plan was to use the attribsize function to separate the attributes per type, but I believe that my code at the moment isn't looking in the right place. int attribType = attribsize(0,"prim",attributes); printf("Attrib %s = %s\n", attributes, attribType); If you have any ideas or solutions it'll be highly appreciated. Thanks!
  5. Hello all, I'm creating an attribute in point VOP and exporting it using bind. I'm also using add attribute within the point VOP to give the attribute a local variable name. I'm also specifying the class as "Detail" Later, I'm adding a node (any node it doesn't matter) to this and in one of the channels I'm trying to reference my attribute by using $MYATTRIBUTE However the result returns as 0, when the value should be 1.0 (it is 1.0 for every point) What am I doing wrong? Thank you.
  6. Cd Attribute Transfer Query

    Hi How could I transfer a Cd attribute along an OBJ such as a pipe. I'm new and one way I know is using another OBJ as a mask Basic Example GIF https://gyazo.com/912405a45452c308514db0ce5da4e64c How could this be done evenly on something more complex whether its a pipe or a detailed mesh. Thanks guys
  7. Hi, first of all sorry if this has already been asked. I'm advecting some particles from a pyro sim. I would like to transfer some attributes from the pyro sim to the pop sim, like density, color, other... I have to use the gasfieldtoparticle node if I'm correct, but I cannot set it up correctly. Here is my DOP network I don't really know the correct way to use this node, could you please enlighten me ? [another question out of topic, do you use win10 on a work machine and do you recommend it?] thanks a lot!
  8. #‎urgent‬ Hello everybody, This is regarding a project I am working on currently. I want to apply material shader with displacement on red portion while the grey areas will have a constant shader. Trick is red portion is animated and moving from point 1 to 2. How to use this red color value to drive my shader from point 1 to 2. Any help is appreciated. Its kind of urgent and I am stuck badly here. Thanks in advance.
  9. VDB from attribute?

    Like the title says, is there any way to duplicate the functionality of the volume from attribute SOP to VDB? I have an animated point cloud with a density attribute that I want to convert into VDB. VDB from particles doesn't give me the results I want...just looking for a straight port of volume from attribute to work with VDB Thanks!
  10. I am attempting to run a twist over a specific group of particles. I create an object to define the area of Interest then use an Attribute transfer to transfer a float value that I want to call in the Twist sop. But when I reference the $TWIST attribute I have created in the strength amount, it throws an undefined variable error. Is it not possible to use Custom Variables in the twist sop? The effect I am trying to achieve is a weighted deformation with controllable falloff, so that there is not a hard line between the deformed and undeformed particles. I'm sure its probably better to do this in a VOPSOP... simple example attached. Thanks guys twist_by_attribute.hip
  11. Animated Viscosity by Attribute (FLIP)

    Hey guys, I just managed to make a viscosity by attribute to work (thx to Rafael Santos e Eetu M.), but now i would like to make it animatable in order to make melting stuff. The problem is that the particles get the viscosisty properties on the 1st frame only. How can I keep updating it based on my attribute vop? My attribute vop setup is pretty simple. I'm just using Hue Shift to change the points color from white to black. Here's an image of my setup: https://www.dropbox.com/s/z67d620mcp9bgdk/varViscosity2.jpg?dl=0 And the file: https://www.dropbox.com/s/rnsoxgmj225ka33/FLIP%20-%20ViscTransfer3.rar?dl=0 Best and thx in advance. Alvaro
  12. Hi, When I select points from the viewport, how do I get a value of point attribute in python? I wrote a beginning like this: 1 import toolutils 2 viewer = toolutils.sceneViewer() 3 selection = viewer.selectGeometry('Get Ids From Select Points',geometry_types = [hou.geometryType.Points]) but I don't know how to continue this. thanks Shawn
  13. I realize that there is some inheritance/hierarchy witchcraft that is stopping my code from compiling properly (undeclared identifier). I have tried many snippets of code that are supposed to create attributes, but they only work inside the cookmysop function. So, how can I create an attribute outside cookmysop() that is at the same time accessible by the cookmysop function and avoids inheritance problems? Thanks in advance.
  14. I want to have possibility to list point or primitive attributes in my menu according to type user will pick. Lets say that my operator default state for attribute type is Point attrbute which I got covered by PRM_Template(PRM_STRING, 1, &attributeParm_Name, PRMzeroDefaults, &SOP_Mantragora::pointAttribMenu); and user switched type to Primitive. Should I update the menu with PRM_Template::setChoiceListPtr(&SOP_Mantragora::primAttribMenu) ? If so, where I should do this? Putting it in cook() method didn't worked. EDIT: The same case is for groups. There is SOP_Mantragora::groupMenu But it lists all group types at once. And I want to have listed only those specified by user and switch between SOP_Mantragora::pointGroupMenu and SOP_Mantragora::primGroupMenu Thanks
  15. Hi, Houdini users. I'm making voronoi test scene now. I've calculated the volume to voronoi fracture in foreach. I want to flag the biggest piece in it. I'm trying few solution but still dose not working. How to search maximum value of attribute? Then how to flag put up these? Thanks! voronoi_test02.hip
  16. Hi, I want to know if it's possible to have an object attribute outputted as file or in a ROP Net node. I have a 1024x1024 grid right now. Each point on the grid represent a pixel. This grid has many attribute and I would love to render a map of all these attribute. I know and tested to copy each attribute to the Cd attrib and render it. It works but I wonder if there is a simpler way. A node for instance that would not need a camera or would not need to copy the attribute to render to the Cd attrib. Ideally I would like to have a render node that renders the top view of an object given attribute. Thx! C
  17. I'm trying to normalize the velocity of an animated Bird. (not sure if normalize is the right word) The bird was animated to flap and fly along a path in XSI then exported to alembic. I want to emit fluids off the bird using the wing flap velocity WITHOUT using the velocity of the bird body moving through space. How would I go about getting rid of the forward velocity? I tried using a centroid point to subtract from the bird velocity in a VOP with hopes that it would leave me with only the flapping velocity but no luck there. I've attached a file with an example setup. Any help would be appreciated, I think I'm missing something simple. normalize bird velocity_v01.hip
  18. Hi everyone, as title says I'm having problem using a custom attribute. Basically I've created an attribute in VOP SOP which is returning the value of the angle between some points. After the vop sop I've appended a transform sop where I want to use this attribute to drive some parms, but the node gives me an error saying "undefined variable". The attribute is a point attribute and I've also tried promoting it to different classes with no luck, it just doesn't get recognized by the transform node. It's probably a silly problem but I'm stucked here. Any kind of help is much appreciated, thanks in advance.
  19. Hi all, I'm a creative C++ coder playing with Houdini - pretty beginner but with some understanding of what's going on. I've cached a flip simulation as BGEO sequence, and I'm having trouble adding custom attributes to the points which are dependent on initial position of the point in respect to the initial shape. E.g. let's say I want to melt a teapot, and I want to to use different triangulation parameters for the body and the spout. I.e. I want to mark the spout as "bodypart"==1 and the body as "bodypart"==2 and create groups based on that. This I know how to do: 1. Load the teapot in a geo node. 2. Cookie the spout with a simple shape hilighting the spout area, do points from volume, attribcreate and assign 1 for bodypart 3. repeat for other parts etc. 4. create a flip fluid out of these points and solve it 5. cache the resulting simulation as a BGEO sequence 6. load the BGEO seq, and all of my points still have the custom attributes, and I can use those for meshing and various other visualisations. This works perfectly and does exactly what I need. However problem with this, is if I decide to add/change body parts, I need to re-run the flip solver which makes no sense since the bodypart attrib has no effect on the simulation. Doing this attrib create before the flipsolver makes sense for things like color and viscosity, but it doesn't make sense for attributes which don't affect the sim I think. what I would like to do is: 1. Load a mesh and select different parts of that mesh and assign only attributes which are essential to the flip solver (e.g. Cd, viscosity etc). 2. create a flip fluid out of these points and solve it 3. cache the resulting simulation as a BGEO sequence containing only attributes which are essential to the flip solver 4. load the BGEO seq, and assign new attributes, which I will use for meshing and various other visualisations. If I use the same method (i.e. volume intersections) on the BGEO sequence, it understandably applies the volume intersection every frame, and so the attributes are re-applied every frame to the points inside the volume, and don't move with the points. What I really need is something like "at frame 1, do the cookie and attrib creation, and then maintain those attributes throughout the BGEO sequence" but I can't figure out how to do that in Houdini. Any tips welcome! P.S. I have 'reduce' set to off in my flip solver.
  20. Or maybe I'm missing something? Can I extract "identyficator" or "type" somehow from this code? <?xml version="1.0" encoding="utf-8" ?> <Nodes> <SOP> <Node identyficator="0"> <Defaults> <Name type="internal">hdk_sop_foo</Name> <Name type ="external">SOP Foo</Name> <Name type="iconname">SOP_Foo</Name> <Name type="iconextension">svg</Name> <Name type="version">1.0</Name> </Defaults> <Parameters> <Parm identyficator="0"> <Name type="internal"></Name> <Name type="external"></Name> </Parm> <Parm identyficator="1"> <Name type="internal"></Name> <Name type="external"></Name> </Parm> </Parameters> </Node> </SOP> <DOP> </DOP> </Nodes> There are only four methods available in UT_XMLNode, and it doesn't look that any of it gives access to attributes.And what is getContents() method returning? WTF is this? I always get blank string with it, so what should be specified in the node to get some data with it?Thanks!
  21. Hello, I'm looking for the equivalent to the pops nodes rotation, velocity, and attribute in dop pops, trying to simply convert a H12 to H13 setup. Not sure if this need be an RFE, or if there is an equivalent already there. Thanks -Ben
  22. Hello. I need you advice about AttribWrangle I have the simple code: setpointattrib(geoself(),"P",0,{10,10,10},"set"); So now I would like to get the attribute value from the current modified geometry. How to do that? Note again: We are in "Run over: detail" I couldn't find any methods to get current attribute value trough geoself() identifier. Please, help
  23. Hi guys, I've been looking into Houdini recently, specifically the FLIP solver. I was wondering if anyone had any thoughts on a workflow for taking an attribute created in a SOP and using it to mask a force. In this case there is a sphere which has particles spawned in the volume, the sphere has two groups made from it which are then converted to attributes. These are colourised red/green in the example image. What I want to do now is use that attribute in DOPs to mask a force so that, for example, a gravity would only affect the red particles. This is after it has gone through the FLIP solver. I know the data is there as I can see it under flipobject\geometry, and I have also used a dopimport in a SOP solver and been able to access those attributes there. I'm just not sure how to access it in the DOP. I know there was a Peter Quint video demonstrating using a poppoint expression in a POP solver to group an attribute, but as far as I know this limits the forces you can use to the pop forces. Also I'm not sure how this would now be applied to Houdini 13's updated POP solver. I was also reading about a point/prim expression in a DOPs group node, but i couldn't figure that out either, and wasn't sure if it was actually finding the attribute. If anyone has some insights they would be greatly appreciated Thanks
  24. Hello, I am still new to Houdini and got the following Problem to solve: I got a fractured Object and want to use a Box to Group a specific area of the fractured Object. BUT I want to select only whole Pieces. In other words: If one or more Primitives with the Attribute NAME are in Box, assign ALL Primitives with same Value of Attribute NAME to Group "X". Example 1: If Prim A (with Atb. NAME = "Piece5") is in Box, assign ALL Prim with Atb. NAME == "Piece5" to Group "X". Example 2: If Prim B (With Atb. NAME = "Piece2") and Prim C (Atb. NAME = "Piece9") are in Box, assign ALL Prim with Atb. NAME == "Piece2" OR NAME == "Piece9" to Group "X". So in the end it should work for n Primitives in Box. How can I achieve this? Thanks in advance Lukas
  25. I am working on a project that uses Vector attributes on a plane to set the velocity attribute of a series of particles. How this is set up now the particles start on a primitave that has an initial vector on it, so they start moving. They travel over a region of primatives with no vector set, which I have the system ignore. Eventually they cross another prim with the vector set and they take the new vector immediately. What I am looking for is a way to detect when they cross over this region and instead of immediately taking the vector, I want to have the change be more gradual over time. Is there any way to do this? I know how to do it for an entire span, but only for specific frames. How do i make it only happen when it detects a change in the velocity vectors.