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Found 86 results

  1. Animate along a Surface

    Hi guys, i have this sphere where i have a geo displacement driven by color, to animate the color attribute i thought i could use another sphere that i can animate on the surface, the problem is that i don't know how i can do it. Anyone have some suggestions?
  2. How the heck does this work?! Within the solver is the attribute Transfer with "Previous Frame" in the left input and the Sphere in the right input. How does the solver know to transfer to the grid when it is not specified in the solver? Transfer_within_Solver.hipnc
  3. How exactly does attribute interpolate work? I have the following network but when I change the mountain SOP the points jump all over the place! I've turned on Prim Num attribute and sourceprimuv attribute in the scatter SOP.
  4. Hey guys, I'm having an issue where the Alpha displays properly in the viewport but doesn't work when rendered. I've done this before, just a simple Constant shader, and it always worked. Here is what it looks like in viewport vs render: I looked at other threads and none of the solutions work in this scene. Here is the scene file: 0007_odforce.hip Thanks!
  5. How can i import attribute to geoself() geometry from second input of wrangle node if i don't know type of this attribute. I write function: parameters: native_input = 0 (first input of wrangle node) sample_input = 1 (second input of wrangle node) attribs = string like "attrib1 attrib2 attrib3" native_ptnum = number of point in current geometry where i want create attributes like in second input sampled_ptnum = number of point from second input where i want sample attribute. but cannon import any array attributes like "Cd" and etc... This function correctly worked only if attribute is not array (type = 0 or 1 or 2) :((( void sampleattribs(int native_input; int sample_input; string attribs; int native_ptnum; int sampled_ptnum ) { foreach(string aname; split(strip(attribs), " ")) { aname = strip(aname); if ( haspointattrib(sample_input, aname) ) { int atype = attribtype(sample_input, "point", aname); if (atype==0) { addpointattrib(native_input, aname, int(0)); int value = point(sample_input, aname, sampled_ptnum); setpointattrib(native_input, aname, native_ptnum, value); }; if (atype==1) { addpointattrib(native_input, aname, float(0)); float value = point(sample_input, aname, sampled_ptnum); setpointattrib(native_input, aname, native_ptnum, value); }; if (atype==2) { addpointattrib(native_input, aname, ""); string value = point(sample_input, aname, sampled_ptnum); setpointattrib(native_input, aname, native_ptnum, value); }; if (atype==3) { int def_value[]; addpointattrib(native_input, aname, def_value); int value[] = point(sample_input, aname, sampled_ptnum); setpointattrib(native_input, aname, native_ptnum, value); }; if (atype==4) { int size = pointattribsize(sample_input, aname); string typeinfo = attribtypeinfo(sample_input, "point", aname); float def_value[] = {}; for(int i=0; i<size; i++) append(def_value, 0.); addpointattrib(native_input, aname, def_value); setattribtypeinfo(native_input, "point", aname, typeinfo); float value[]; resize(value, size); int success = -1; //value = point(sample_input, aname, sampled_ptnum); //printf("%d\n", sampled_ptnum); //foreach(float v; value) { printf("%f", v); }; setpointattrib(native_input, aname, native_ptnum, value); }; if (atype==5) { string def_value[]={}; addpointattrib(native_input, aname, def_value); string value[] = point(sample_input, aname, sampled_ptnum); setpointattrib(native_input, aname, native_ptnum, value); }; }; }; };
  6. anyone know how can i read a value from a frame number ? for example in frame 40 and want to access an attribute value at frame 20. is this possible to do this via expression ? tnx
  7. hi, I want to control the emission of my particles via attrib. E.g. Cd, or a custom attrib it doesnt matter. In the attached example file I animated some points to get white after frame 30. When I use Cd for emission after that in the pop network it spawns particles everywhere on the surface until frame 30 is reached and than it uses the attribute as expected. Can I control the emitter in the particle network with attributes like if (@Cd> 0.5) ---> spawn!! if not - dont spawn anything. Or with a custom attribute like if(@heat > 30 ) spawn particle....etc. Or is this better achieved in another way in houdini? Thank you in advance. kind regards Jon attrib_as_emit_value.hiplc
  8. Hello, I'm looking for the best way to prevent an attribute from changing once it has reached a certain value. I'll have other benefits from this, but for now it's to control the "active" state of some points via an animated object. I'm setting a group of point with a bounding sphere grouping, then I wrangle i@active = 1 for that group. but, obviously, when a point is back out of the sphere, it's out of the group and gets a @active = 0 again. I'm wondering if it's doable in VEX (if active becomes 1 then never change again) or if there's other tricks to do that. here is a simple hip file where I move the points up when they are in group1, so for this exemple, I would like the point to never come back down if they get moved. Thank you! I've seen a way to do that in a particle tutorial, where the colours get changed and is then prevent from changing back when outside a box, but I just can't remember, and can't get my hand on that video again : / OD-F_keepattrib.hipnc
  9. Hey guys, first post here. I'm extremely noob at Houdini and I've got a very basic question. I've got a particle system going, and after the POPs system in the Source Particles SOP it creates, I'm trying to use the Y position of each particle to drive a Blend Sequence that is copied onto the particles with a Copy SOP. What I haven't been able to find is how to query the Y position of my particles. I can find their positions with the Geometry Spreadsheet, but the name of the attribute it gives me is "P[y]", and typing that into an expression doesn't seem to work. I had thought it might be "@P.y" but that errors out as well. I think one of the problems is that I'm not telling Houdini WHAT to find the Y position of. But again, not sure how to find that. I've googled and did a cursory search of the forums here but all the posts I've found are way more advanced than this simple thing I'm trying to find Can you fine gentlemen/ladies point me in the right direction to find how to query this sort of basic data? wk2_copy.hipnc
  10. Hi all! I'm pretty noob with houdini so maybe this will be a silly question :-) As the title says, I can't find a "direct" way to access to global variables in point/attribute wrangle nodes( maybe it's not possible?). In my case I would access to $NFRAMES global variable to pass as parameter in fit() function to normalize frames count, but obvioulsy as reference guide say: Now I found a workaround: I create an attribute(with attributeCreate node) with $NFRAMES as value and then I can access in the wrangle code snippet. It works but I don't like this method because: for now I have just a bunch of points and the memory footprint is relatively low but what if I crank up the value for thousands of points? if I'm not wrong, integer values are handled as C small int so 4bytes*100.000 points will increase the memory footprint( I know that are just of bunch of KB but I'm "obsessed" with time/space performance). There are some "clean" way of get global variables? Thanks in advance
  11. create piece size attribute

    Hello everyone, I am fracturing a geometry and need to delete the pieces bellow a certain size. My problem is that I don't know how to delete based on size. My guess is I need to create a size attribute somehow and then delete based on that. I am sure this should be pretty straight forward but couldn't find any info on that, please give me some ideas, thanks!
  12. 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?
  13. 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.
  14. 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!
  15. 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!
  16. 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.
  17. 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
  18. 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!
  19. #‎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.
  20. 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!
  21. 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
  22. 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
  23. 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
  24. 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.
  25. 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
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