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Houdini Indie and Apprentice » How to randomise the colors on a Ramp node?
- jsmack
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delete the ramp and make a new one, then don't touch it. edit the values on the builder node's parameters.
Solaris and Karma » Karma Overlay vs RS / Arnold Overlay
- jsmack
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This is fixed in a future version of Material X
https://github.com/AcademySoftwareFoundation/MaterialX/commit/78d27622a0edc00f4936d7d7c613b29f5d181fe0 [github.com]
https://github.com/AcademySoftwareFoundation/MaterialX/commit/78d27622a0edc00f4936d7d7c613b29f5d181fe0 [github.com]
Houdini Indie and Apprentice » How to randomise the colors on a Ramp node?
- jsmack
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WanderingOwljsmack
There is a level above that is implied, but doesn't exist until render time. Unfortunately, that means you can't animate it. You can create that level above explicitly by creating a material builder node and creating the material inside. This will allow parameters to properly instantiate on a parent level for interaction and animation.
That's great, thank you so much! Can I double check what kind of material builder you're referring to - I get options for Karma, VEX, USD and USD Preview when searching it up. Anything special I need to do to add this material to my model, also? I feel like I'm missing something since the click-and-drag and material node methods aren't working with the ones I've tried so far.
oh I forgot the renamed it in Houdini 20. It used to be the only one. It's the VEX material builder. It should drag and drop the same as any other VOP in /mat, but the material sop or material parameter on the object are other ways to pick the material.
Houdini Indie and Apprentice » How to randomise the colors on a Ramp node?
- jsmack
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WanderingOwl
For context - this is taking place directly within the /mat network, so there isn't any level above it. hip file is a bit of a mess rn but hopefully the screenshot helps.
There is a level above that is implied, but doesn't exist until render time. Unfortunately, that means you can't animate it. You can create that level above explicitly by creating a material builder node and creating the material inside. This will allow parameters to properly instantiate on a parent level for interaction and animation.
Technical Discussion » Question : for each primitive in vex
- jsmack
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I'm not sure what you're after, but you don't need a for each loop block in sops just to enumerate primitives in VEX. On the wrangle, change the run over to primitive, and @primnum will be the number of the current primitive. The for each loop block is only needed for isolating parts of the geometry and running a set of nodes over each isolated part.
Houdini Indie and Apprentice » How to randomise the colors on a Ramp node?
- jsmack
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If you hit 'u' to go up a level, do you see your ramp again on the parent node's parameters? If so, this is where you want to animate.
Solaris and Karma » Shutter shape aka shutter efficiency
- jsmack
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jarjarshaq
Does Karma have a shutter shape like Mantra? Other renderers call it shutter time (prman) or mental ray ()called it shutter efficiency.
I think this lives on the karma physical lens shader now
Technical Discussion » instance point's color not work in material
- jsmack
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Ah, this tripped me up before too. Don't use the second input of the instance node. This uses a points prim that's already been translated as USD. It will not inherit any attributes from USD points.
Attributes can be inherited from SOP points. To instance on SOP geometry, either put the instance points inside the instance node, or set the 'external SOP' path to point to the SOP geometry containing the instance points.
Attributes can be inherited from SOP points. To instance on SOP geometry, either put the instance points inside the instance node, or set the 'external SOP' path to point to the SOP geometry containing the instance points.
Technical Discussion » How to use AO map with Principled Shader?
- jsmack
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You don't use an ao map with a photorealistic material. The lighting is calculated using path tracing.
There is a "passthrough" slot on some baking materials that tell the exporter which map will be the ao map on export. The principled material might not have this passthrough slot.
There is a "passthrough" slot on some baking materials that tell the exporter which map will be the ao map on export. The principled material might not have this passthrough slot.
Solaris and Karma » Texture sequence manipulation in material x
- jsmack
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BradThompson
Thanks jsmack! Today I learned that $F is an float (or int?) and $F4 is a string. Now it works.
It's a float. hexpressions only have two types, string and float. There's a lot of gotchas in the expression language that stem from the strict typing. stuff like why are there point() and points() functions.
Solaris and Karma » Texture sequence manipulation in material x
- jsmack
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BradThompson
$JOB/mytexture/`$F4-10`/.exr
you mean this?
$JOB/mytexture.`padzero(4,$F-10)`.exr
`$F4-10` doesn't mean anything, since $F4 is a string not a number.
Edited by jsmack - April 26, 2024 15:20:16
Solaris and Karma » adding two materials together?
- jsmack
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cdordelly
I might be wrong but that additive surface operation can be emulated with BSDF nodes too right? I guess there might be some limitations compared to what we have in RS.
BSDF nodes don't work with XPU
Solaris and Karma » adding two materials together?
- jsmack
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soulcage_dpt
probably this was asked before, but i want to "add" (not mix) two materials together to achive a specific look.
adding a constant (unlit) shader, that has a texture applied, and a diffuse shader, that is white and gets the lighting.
It's not possible to add materials, but in your case you could connect the emission to the emission input on the standard surface that makes up the diffuse shader. The standard surface is already adding up the layers that make it up.
soulcage_dpt
(and does the mtlx-ambient-occlusion not working in karma XPU?)
No, it's not supported in XPU.
Houdini Indie and Apprentice » How to use distance for effect fall off ?
- jsmack
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woltieljsmackCould you provide an example, i'm new to houdini stuff i don't know how to remap values, or how would it achieve what i need. I'm definelty intersted though how to do that with nodes. Thank you!
Another option without using any code would be to use the distancefrom nodes (geometry, target, etc) to get the distance, and use the mask section to remap the values or the attribremap node after the fact to shape the falloff. I don't think there's a non-code way to do a power function, but it would be a lot less code The remap attribute ramp set to b-spline could give parabola-ish falloff. Then use attribcombine to add the noise masked by the falloff attribute to P.
the nodes to use to replace VEX code for remapping and combining are Attribute Remap, Attribute Combine, and Attribute Adjust. To apply the displacement to position, use another attribute combine or a transform by attribute. I like to use nodes that imply what they do. In my example I've only used one bit of vex, and that was to generate a group of the closest point for uses with the surface distance node since it requires a point group to compute distance along the surface towards.
Houdini Indie and Apprentice » Texture look like Premultiplied
- jsmack
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Are you trying to disable alpha premultiplication in the 3d viewport? I don't think it's possible.
Houdini Indie and Apprentice » How to use distance for effect fall off ?
- jsmack
- 7801 posts
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Another option without using any code would be to use the distancefrom nodes (geometry, target, etc) to get the distance, and use the mask section to remap the values or the attribremap node after the fact to shape the falloff. I don't think there's a non-code way to do a power function, but it would be a lot less code The remap attribute ramp set to b-spline could give parabola-ish falloff. Then use attribcombine to add the noise masked by the falloff attribute to P.
Edited by jsmack - April 24, 2024 20:30:04
Technical Discussion » Vex: Fix Backslashes into Frontslashes
- jsmack
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backslash is the 'escape character' in several languages. if you want a literal backslash, it needs to itself be escaped with another backslash. depending on how many layers if indirection, it could take more than one extra backslash to get a literal backslash. I tend to start at two and use trial and error to find out how many it needs. wrangles need to put at least three or four in place of one to work, but it depends on how they get in the code.
Houdini Lounge » Changed Normal SOP behaviour?
- jsmack
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P and N are special, it's considered illegal to have multiple classes of P and N. You can use a different name for N if you need multiple classes of attribute storing the normal.
Technical Discussion » why the skin twisted??
- jsmack
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Sounds like the subdivision is using the catmull clark algorithm on the quaterion orientation attribute naively. This attribute defines the twist on the curves when skinning. If you just want noodles, you can probably remove the orientation attribute created by the simulation. Otherwise, the only fix is to not subdivide the orient as a quaternion. If you decompose the orient to a normal and up vector, the subdivision will still be mostly valid and won't result in flips. I would file a bug too.
Solaris and Karma » thin film doesn't work with metalness at 1
- jsmack
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Thin film is only implemented in the dielectric bsdf. Complex IOR with thin film interference is not yet implemented. You can file an RFE to ask for it to be implemented.
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