Oh crickey! That's a lot more involving than I thought! I wanted to add them into Lsystems and thus get nice flowerbuds and cactus geometry but holy moley it's much trickier than I expected!
Strange, I'd have thought the way metaballs work would make it almost trivial, like a checkbox or pull down menu…
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Houdini Indie and Apprentice » Pushing Metaballs?
- Soothsayer
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Houdini Indie and Apprentice » Pushing Metaballs?
- Soothsayer
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Standard metaballs merge into each other like blobs of slime.
Can I use metaballs that push into each other like balloons?
I can change the weight into the negative but then the balls dissappear.
Can I use metaballs that push into each other like balloons?
I can change the weight into the negative but then the balls dissappear.
Houdini Indie and Apprentice » Growing LSystems towards targets
- Soothsayer
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Thanks Jeff. Very useful help. I'll dive into that. At the moment I can make it grow towards the target. At each increase in generations though it changes its initial shape. It think the whole system gets recalculated completely at each step, rather than appended to the old bit.
Houdini Indie and Apprentice » Growing LSystems towards targets
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Thanks Arctor, I'll have a look at that too.
But first I need to know how to reference stuff in expressions.
Sorry, I can't express myself very well. I'll need to get used of the Houdini lingo… I attached an image.
But first I need to know how to reference stuff in expressions.
Sorry, I can't express myself very well. I'll need to get used of the Houdini lingo… I attached an image.
Houdini Indie and Apprentice » Growing LSystems towards targets
- Soothsayer
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I had a more detailed look at the LSystems. I think the $(,x,y,z) turtle command does what I want.
In the LSystem Rules tab I have entered $(b,c,d) in “Rule 1”. The b,c,d variables are in the Values tab.
Question: How do I make those b,c,d variables the same as those of the box position in the scene (modified via the VOPSOP)?
I want the LSystem to grow towards the box, wherever I place it.
In the LSystem Rules tab I have entered $(b,c,d) in “Rule 1”. The b,c,d variables are in the Values tab.
Question: How do I make those b,c,d variables the same as those of the box position in the scene (modified via the VOPSOP)?
I want the LSystem to grow towards the box, wherever I place it.
Houdini Indie and Apprentice » Growing LSystems towards targets
- Soothsayer
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I'd like to grow LSytems towards targets. Is there a standard way to do this or do I need to come up with a custom solution?
My idea is to build a VOPSOP network that creates 2 custom attributes to vary the angle and length of the LSystem elements according to the tree-branch position relative to the target(s).
One problem I can see with this is that it may not be possible to access those points on an LSystem where growth occurs (the postition always refers to the whole Lsystem's object?)
Any ideas on other approaches? Dynamic rigs?
My idea is to build a VOPSOP network that creates 2 custom attributes to vary the angle and length of the LSystem elements according to the tree-branch position relative to the target(s).
One problem I can see with this is that it may not be possible to access those points on an LSystem where growth occurs (the postition always refers to the whole Lsystem's object?)
Any ideas on other approaches? Dynamic rigs?
Houdini Indie and Apprentice » who can tell me what the "LevelSet" actually is? i
- Soothsayer
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I don't know the Houdini specifics but the term is quite general. Imagine several objects in a room that emit heat. You could sample points in that room and assign each of them a temperature value. You could then take all the points that equal, say 23 degrees celsius. That would be a level set. If you were to make a surface with those points you'd have an isosurface.
Houdini Indie and Apprentice » "Converting" functions
- Soothsayer
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OK, here's the scene! I think this is as far as I will take it for now. (it needs a lot of cleaning up)
On my machine, switching on threading results in a slower display and weird artifacts.
There's one more question I have: Is there a node inside VOPSOPs that transforms input values via a visual function curve (like a bezier spline). There's a node like that in XSI (called Fcurve) and it is very useful. I found a Spline node in VOPSOPs but it is not visual and I'm not sure how to use it.
On my machine, switching on threading results in a slower display and weird artifacts.
There's one more question I have: Is there a node inside VOPSOPs that transforms input values via a visual function curve (like a bezier spline). There's a node like that in XSI (called Fcurve) and it is very useful. I found a Spline node in VOPSOPs but it is not visual and I'm not sure how to use it.
Houdini Indie and Apprentice » "Converting" functions
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OK, thanks. It appears to work now! I just need to tweak the hole thing quite a bit … Maybe I can post the final scene when I deem it acceptable enough!
Houdini Indie and Apprentice » "Converting" functions
- Soothsayer
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OK, I can now get data in and out of VOPSOPs. I put a VOPSOP in my scene that's called “wave modifier”. That's where I get the ray SOP data in. But, I think that the ray-sop is not doing what I thought. How do I find out what kind of data a node spits out? Vectors? Scalars? Points? As I understand it the ray-SOP moves points closer to another surface.
What I am really looking for is a node that takes a point, shoots a ray from it, and gives me the distance (or vector) to the first surface it intersects. In XSI we have a “raycast” node for that. Think of it as a sonar!
I want to use the depth data to weigh some wave properties. With it, I should be able to refract waves around obstacles for example.
As for bugs, I think I found 2. The VOPSOP parameter sliders don't update during playback. I also get a lot of “memory allocation” crashes when messing with the VOPSOPS.
(By the way, the waveform SOP and Ocean Toolkit look very good, but I am using this experience to evaluate Houdini against XSI.)
What I am really looking for is a node that takes a point, shoots a ray from it, and gives me the distance (or vector) to the first surface it intersects. In XSI we have a “raycast” node for that. Think of it as a sonar!
I want to use the depth data to weigh some wave properties. With it, I should be able to refract waves around obstacles for example.
As for bugs, I think I found 2. The VOPSOP parameter sliders don't update during playback. I also get a lot of “memory allocation” crashes when messing with the VOPSOPS.
(By the way, the waveform SOP and Ocean Toolkit look very good, but I am using this experience to evaluate Houdini against XSI.)
Houdini Indie and Apprentice » "Converting" functions
- Soothsayer
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OK. I've added some stuff and it works nicely now.
I still have some question about the nodes.
1) How can I change the input and output names of nodes such as “multiply” and “subnet”. They have default names such as “input1”.
2) I want to drive some of the parameters from outside the vopsop. For example D (depth) should get its values from the distance of a wave-surface-point to the ground (box in my example scene). I guess the “ray” node does that but how do I get it to work inside the vopsop?
3) Adding several copies of the vopsops sequentially one after the other doesn't sum up the waves correctly. I want to try it “in parallel” with something akin to the math node in CHOPs. Can it be done?
I still have some question about the nodes.
1) How can I change the input and output names of nodes such as “multiply” and “subnet”. They have default names such as “input1”.
2) I want to drive some of the parameters from outside the vopsop. For example D (depth) should get its values from the distance of a wave-surface-point to the ground (box in my example scene). I guess the “ray” node does that but how do I get it to work inside the vopsop?
3) Adding several copies of the vopsops sequentially one after the other doesn't sum up the waves correctly. I want to try it “in parallel” with something akin to the math node in CHOPs. Can it be done?
Houdini Indie and Apprentice » "Converting" functions
- Soothsayer
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I tried to add some nodes into the network to further define some values. The nodes are in the vopsop1 and are called gamma, k_mag, and w_noDepth. But the nodes make the whole thing not work.
What is going wrong? If I delete them it works again.
What is going wrong? If I delete them it works again.
Houdini Indie and Apprentice » "Converting" functions
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Thanks, I'll try that when I get home. Takes a while to get my head around this!
That's very useful to have the variables automatically exposed on the SOP level.
That's very useful to have the variables automatically exposed on the SOP level.
Houdini Indie and Apprentice » "Converting" functions
- Soothsayer
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Actually, none of the variables seem to have any effect. I am changing the values in the Parameter window, scrolling down to the “Numerical Defaults”.
I also get the Houdini Console popping up with “Error reading SVG:”
Sorry for me being so stupid!
I also get the Houdini Console popping up with “Error reading SVG:”
Sorry for me being so stupid!
Houdini Indie and Apprentice » "Converting" functions
- Soothsayer
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Wow! Thanks Edward, that works beautifully (try a grid)!
But how did you get the time in there? If I dive into angle_rad I see a node called global1. That gets the point positions, right?
I'm actually trying to replicate this:
http://www.ep.liu.se/ecp/028/004/ecp072804.pdf [ep.liu.se]
There's a lot of fluff in that article, so for the moment I'm trying to get (2) and (3) working first.
Changing the values of k doesn't change the wave direction . Everything looks right and logical in the VOPs though.
Are there any xsi-like visual debug tools in Houdini?
But how did you get the time in there? If I dive into angle_rad I see a node called global1. That gets the point positions, right?
I'm actually trying to replicate this:
http://www.ep.liu.se/ecp/028/004/ecp072804.pdf [ep.liu.se]
There's a lot of fluff in that article, so for the moment I'm trying to get (2) and (3) working first.
Changing the values of k doesn't change the wave direction . Everything looks right and logical in the VOPs though.
Are there any xsi-like visual debug tools in Houdini?
Houdini Indie and Apprentice » "Converting" functions
- Soothsayer
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edward
I thought x0 and z0 were also vectors because were in bold. How do you take a 3-vector and do a dot product with a 2-vector?
Ah! k is a 2 vector too. Sorry, mistake! ops:
Houdini Indie and Apprentice » "Converting" functions
- Soothsayer
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Thanks, I'll have a look at that later (don't have Houdini on this machine at the moment). As for the variables:
p0 = (x0, z0) is a 2-vector for every point P on the surface giving the x and z coordinates (so, p0, p1, p2, p3, …pn respectively) . I suppose that would have to be split into 2 channels if I use CHOPs?
y is just the y coordinate of a point P
k is a scalar
k is a 3-vector (a direction vector)
A is a scalar
w is a scalar (phase)
t is a scalar (time) (($ in Houdini?)
The whole formula would be applied to every point on a mesh at each frame to create an animated surface.
p0 = (x0, z0) is a 2-vector for every point P on the surface giving the x and z coordinates (so, p0, p1, p2, p3, …pn respectively) . I suppose that would have to be split into 2 channels if I use CHOPs?
y is just the y coordinate of a point P
k is a scalar
k is a 3-vector (a direction vector)
A is a scalar
w is a scalar (phase)
t is a scalar (time) (($ in Houdini?)
The whole formula would be applied to every point on a mesh at each frame to create an animated surface.
Houdini Indie and Apprentice » "Converting" functions
- Soothsayer
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I'm evaluating Houdini by translating a XSI job into Apprentice. I want to modify points on a surface according to a certain function.
p = p0 − (k/ k) * A * sin(k · p0 − w*t)
and
y = A * cos(k · p0 − wt)
where the bold ones are vectors, and the point p0 = (x0, z0)
How would I “convert” such a function into something Houdini can understand? In XSI ICE we have low level nodes such as dot multiplication for vectors, or nodes that create vectors from scratch (such as k in this example)
I think I can use CHOPs to do this but I'm not sure how to modify the channels according to the above formula. Are there low level nodes for this, or would it be written in expressions. How do I dot-multiply in expressions?
p = p0 − (k/ k) * A * sin(k · p0 − w*t)
and
y = A * cos(k · p0 − wt)
where the bold ones are vectors, and the point p0 = (x0, z0)
How would I “convert” such a function into something Houdini can understand? In XSI ICE we have low level nodes such as dot multiplication for vectors, or nodes that create vectors from scratch (such as k in this example)
I think I can use CHOPs to do this but I'm not sure how to modify the channels according to the above formula. Are there low level nodes for this, or would it be written in expressions. How do I dot-multiply in expressions?
Houdini Indie and Apprentice » Channel SOP ?
- Soothsayer
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Oh ok. Thanks for the explanation. I think it would have been very frustrating figuring that out by myself…
I still can't see where I went wrong though (following the blog's video).
Anyway. Solved! Thanks!
I still can't see where I went wrong though (following the blog's video).
Anyway. Solved! Thanks!
Houdini Indie and Apprentice » Channel SOP ?
- Soothsayer
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Hiho. I'm trying to jump ship from XSI to Houdini but having some troubles.
I am following the “CHOPs Deforming Geometry: Part 1” tutorial on the old school blog. I placed a grid node, followed by a null node. I want to put a “channel” node after that but can't get it. I see a lot of nodes relating to rigs but none called “channel”.
Did I press a strange button or something? Where did the channel node go?
:roll:
I am following the “CHOPs Deforming Geometry: Part 1” tutorial on the old school blog. I placed a grid node, followed by a null node. I want to put a “channel” node after that but can't get it. I see a lot of nodes relating to rigs but none called “channel”.
Did I press a strange button or something? Where did the channel node go?
:roll:
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