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## Popular Content

Showing most liked content since 08/17/2019 in all areas

1. 16 points

## 25th Anniversary of Jeff (Old School) Wagner joining SideFX!

Hello Houdini Users, Today we celebrates the 25th Anniversary of Jeff (Old School) Wagner joining SideFX! Over the past 25 years Jeff has helped so many of our customers learn Houdini through his detailed Tech Support replies. His insightful online tutorials. And his enthusiastic live presentations. Jeff has never run out of exciting new things to show us in Houdini, (and Prisms in the early days). If you would like share your experiences of watching Jeff's classes please do so. And take a moment to wish him a Happy Anniversary! All the best, Jenny Blacklock. Technical Support Manager SideFX
2. 10 points

## biological modelling methods

Great stuff, Nicolas. This is starting to look Giger-like already! You don't necessarily need to create UVs in SOPs, though. To project textures on those VDB meshes it's arguably more efficient to do in a shader: 1) Transform position to world space. 2) Curve IDs shown as random colors. 3) U value from curves in HSV colors. 4) Direction to nearest curve position. 5) Tangents from curves set to absolute. 6) Direction to curve oriented along tangents. 7) V coordinate enclosing each wire. 8) UV coordinates in red and green. 9) UV mapping an image texture. 10) Texture based displacement along curves or at least what happens when mandrills do the job ; ) The material snippet: string geo = 'op:/obj/curves/OUT'; P = ptransform('space:current', 'space:world', P); int prim = -1; vector uvw = vector(0.0); float dist = xyzdist(geo, P, prim, uvw); vector pos = primuv(geo, 'P', prim, uvw); float u = primuv(geo, 'u', prim, uvw); vector tangent = primuv(geo, 'tangentu', prim, uvw); matrix3 rot = dihedral(tangent, {0,1,0}); vector dir = normalize(P - pos); vector dir_mod = dir * rot; float v = fit( atan2(dir_mod.z, dir_mod.x), -M_PI, M_PI, 0.0, 1.0 ); P = set(u, v, 0.0); curly_curves_shader.hipnc
3. 7 points

## Complex growth or destruction effect in recent movies

Not that recent, but excellent execution:
4. 5 points

## Procedurally reverse objects

if each of your pieces is mostly enclosed then you can measure volume per piece, if it's negative, it's inverted ts_reverse_inverted_pieces.hip
5. 4 points

1. Regarding the pinch: You can get rid of it by either setting the 'destination min' of fit2 to something greater than 0. Or by simply unplugging it from the next node called smooth2. 2. Regarding a more casual solution on arbitrary curves: There is no shame in using standard SOP nodes. The resample node can create a U attribute running along each curve from 0.0 to 1.0. The color node maps float attributes such as U. The attribute transfer node blends those colors to the grid by taking some nearby samples. .. which can then be smoothed even further by an attribute blur node. In a VOP measure the distance with xyzdist, tune the result with a curve ramp and mix your gradients against a solid background color. colorcurve.hipnc
6. 4 points

## Genetic Algorithms in Houdini

I am not sure if this is the appropriate forum. I recently wondered how hard it would be to implement genetic algorithms in SOPs. The particular example I was curious about was if I could turn a box into a sphere by optimizing for a target function that maintains volume but minimizes surface area. Overall, this was easier than I thought and did not involve all that much code. I ended up recording a video that explains this: The underlying motivation was to get this working in PDG but I figured I had to start with SOPs first. Let me know what you think.
7. 4 points

## biological modelling methods

Hi Mirabela, you could trail curl noise and mesh it with varying thickness. Finer details could originate from a displacement shader utilizing to the same curves again. curly_curves.hipnc
8. 3 points

## The Book of Shaders in Houdini Vex

Hi People! this has a lot of potentials I think sources ---- https://github.com/JosephFiola/BookofShadersHoudiniVex https://thebookofshaders.com Joseph "While Houdini does support GLSL code to render shaders into the viewport, I have not implemented this yet. For now these examples are only visible in the render view using the Ray Tracing render engine." We have examples for 2 and 5 chapters .....if you plug inline-code in CD on Point Vop, you can see everything..and its easy to manipulate.. I am interested to know some process ( Just what to change ) and appreciate help with this. converting rest of some chapters like patterns for example to inline code https://thebookofshaders.com/09/ https://thebookofshaders.com/08/ Thanx
9. 3 points

## Fuel Based Rocket Launch

I put together a fuel based version of the basic density based starter rocket launch scene. This scene includes a couple of additions, that I have seen posted, here on OdForum, including Fencer's smoke drag, based upon distance from origin, and hand drawn velocity curves to encourage the smoke to travel along the curve shape. The support nodes for the hand drawn velocity are shaded purple, in the DOP network. Play around with the fit values on the gas wrangle to alter damping. Increase popnet particle count to send more fuel into the system. Increase popnet life to make fuel linger, longer. ap_rocket_lift_off_fuel_based_090919.hiplc
10. 3 points

When decorating three-dimensional meshes I usually rotate() the directions from N to up so they are horizontal for atan() to work properly. float radius = chf('radius'); float tol = chf('tolerance'); int pt_near = nearpoint(1, v@P); vector pos_near = point(1, 'P', pt_near); vector nml_near = point(1, 'N', pt_near); float dist_near = distance(v@P, pos_near); vector dir = normalize(v@P - pos_near); vector up = set(0,1,0); matrix3 m = dihedral(nml_near, up); dir *= m; float angle = fit( atan(dir.z, dir.x), -M_PI, M_PI, 0.0, 1.0); vector color = hsvtorgb(set(angle, 1.0, 1.0)); float width = abs(dist_near - radius) < tol; v@Cd = color * width; color_wheels_3D.hipnc
11. 3 points

You can create lots of color wheels around points on a grid: float radius = chf('radius'); float tol = chf('tolerance'); int pt_near = nearpoint(1, v@P); vector pos_near = point(1, 'P', pt_near); float dist_near = distance(v@P, pos_near); vector dir = normalize(v@P - pos_near); float angle = fit( atan(dir.z, dir.x), -M_PI, M_PI, 0.0, 1.0); vector color = hsvtorgb(set(angle, 1.0, 1.0)); float width = abs(dist_near - radius) < tol; v@Cd = color * width; color_wheels.hipnc
12. 3 points

## biological modelling methods

I posted some results of first tries of adapting your workflow on my behance, Konstantin, i hope it's not a problem for you. https://www.behance.net/gallery/85035827/Dogs-of-Tindalos
13. 3 points

## Genetic Algorithms in Houdini

Here is the second part - still with music and higher screen resolution though. If I end up doing another one of these, I will increase the UI size in Houdini. The application was to find simulation parameters for a tree simulation. The parameters subtly depend on each other which makes genetic algorithms reasonably suitable. The real challenge is expressing the target function. In my case, I just used the volume of the convex hull but the total length of all wires may be another interesting one to consider.
14. 3 points

## Custom AOV with V-Ray ?

Haha, well, marketing guys promised they'll try to think of something. As to the custom AOVs - it's now supported. You can even isolate the AOV to specific primitives inside an instance hierarchy(e.g. agents) using attributes. We kind of forgot about it, and nobody asked during the Beta. All the best!
15. 3 points

Hi Tim, you can create a wheel by color-mapping the arctangent of your point positions. The smooth function's rolloff parameter can then be used to control the bleeding amount around the circle. colorwheel.hipnc
16. 3 points

## Wireframe and UV Distortion with mantra

For a wireframe shader with consistent line widths, first create a primitive attribute that contains all point positions. Then inside a shader choose point pairs for ptlined() to determine the shortest distance to your shading position to check against a custom wire width. // primitive attribute with point positions int pts_prim[] = primpoints(0, @primnum); v[]@pos = {}; foreach(int pt; pts_prim){ vector p = point(0, 'P', pt); append(@pos, p); } // shader snippet feeding point positions into ptlined() // determining shortest distance to check against wire width. int num = len(pos); float dist = 1e6; for(int i = 0; i < num; i++){ vector pos_0 = pos[i]; vector pos_1 = pos[(i + 1) % num]; float dist_curr = ptlined(pos_0, pos_1, P); if(dist_curr < dist){ dist = dist_curr; } } stroke = dist <= stroke; wireframe.hipnc
17. 3 points

## Smooth outline of 2D pointcloud

if connect adjacent points provides good enough outline for your pointcloud then you can as well just use Triangulate 2D + Divide SOP to get exact outline, which will even match outline points nr_foot_outline_alt.hiplc
18. 3 points

## biological modelling methods

Thanks a lot for your answers, i will dig the two options you propose tonight. Konstantin, your solution would work for pure procedural shading, or with triplanar maps, but you could not generate UV out of it right? Meanwhile i was playing with super simple polar UV projection and got nice results, here is a test render, but it will not do the trick for more detailed image based displacement.
19. 3 points

## Cut a moving object with solver ?

Hi Antoine, to continuously remove parts, it's more reliable to do the subtractions in a voxel field rather than immediately on the mesh. saw.hipnc
20. 2 points

## Vector Field visualization Guide Smoke

change the gasmatchfield1 rank to "Vector" instead of "Scalar"
21. 2 points

## The little things about houdini

I've been using Houdini for over 20 years. You? What I mean is, have you spent long enough working in Houdini to get used to it? These are just my opinions. 01. If it can be easily changed with a line of code in the 123.py then it doesn't need to be hard coded in the gui. 02. You say project a few times. That's not the terminology. It's a hip file, or document. The project is part of the hierarchy that contains a directory for hip files along with other directories. But yes, a "*" next to the file name saying it hasn't been saved after the latest change would be great. You should submit an RFE for that. I bet other people have. 03. Preview of what? A view of the network? Which network? The last render? Which render? Where would the preview go? 04. Nah. Why? Cross platform drag and drop is sketchy. If you can do it with a script then you already have it. Importing with a file SOP is reliable. 05. It's not annoying to open another Houdini. I do it all the time. These aren't web browser tabs. If you want to work across a bunch of hips consider putting them in the same hip file or building digital assets. 06. The curve SOP? The draw curve shelf tool? What's missing? You can absolutely select multiple points. 07. Yes, the Font SOP kind sucks, but it's bare bones and works. Houdini is not a text editor or a vector design tool. If you need something fancier then do it in Photoshop, Gimp, illustrator, or Inkscape then import it as an eps or ai or exr or png or whatever. 08. Yea, the gui customization could use a tool for tweaking it, but I'd put that way on the bottom of the list. Houdini Dark/Light/Pro is kinda lame. But it works well enough for me and keeps too many people from sliding down the endless rabbit hole of pointless gui customization. And sure, the gradients are a little funky, but whatever.
22. 2 points

Hey @Aizatulin & @srletak Sorry for the delay in getting back... Thanks for these solutions - especially the latest side-by-side Aizatulin. I've been working on a setup on/off all week & I think I'm pretty much there now with the combination of what to do in vex/vops. It got a little more complex as I've decided to try and implement displacement which is based on the above techniques, however with some separate controls, so I'm just tweaking & learning as i go. I'll see how far i can get over the weekend & with a little luck post some updates sometime soon. Thanks again to everyone who has replied!!
23. 2 points

## Sierpiński triangle with VEX

Cool. I changed the code that you gave me and made this, it's almost the same. sierpinski.hip
24. 2 points

## Sierpiński triangle with VEX

Here are other examples using the foreach node (with less spaghetti node mess ): Sierpinski 3D Sierpinski 2D Koch Curve foreach_examples.hipnc
25. 2 points

## Sierpiński triangle with VEX

Here is a modification. sierpinski_cloud.hipnc
26. 2 points

## Sierpiński triangle with VEX

Here is an approach using 3 for loops (the inner can be avoided). I do not really like this approach, because I'm pretty sure, that there much more elegant solutions out there (even without recursion). sierpinski_vex.hipnc
27. 2 points

## clifford torus effect

Hi @angelous4x you have an idea I have an idea, + + = maybe. transform before /\$PI *2 = x and y Confuse a cat play with this and your idea. complex math find http://wordpress.discretization.de/houdini/ //q=(1+i+j+k)/2 must be 1 Möbius strip float cos = v@P.z; float sin = v@P.x; float r = v@P.y; float c_sqr = pow(cos,1) -pow(sin, 1); float s2 = 1*sin*cos; vector C = set(c_sqr, 0, s2); vector B = {0, 1, 0}; vector N = cos * C + sin * B; v@P = C + r * N; //Sudanese surface. vector4 gamma(float t) { return set(cos(t), sin(t), 0, 0); } vector4 N(float tau; float t) { float tau_t = tau * t; return set(0, 0, cos(tau_t), sin(tau_t)); } vector4 f_tau(float tau; float x; float y) { return cos(y) * gamma(x) + sin(y) * N(tau, x); } vector sigma(vector4 v) { return set(v.x / (1 - v.w), v.y / (1 - v.w), v.z / (1 - v.w)); } float tau = chf("tau"); vector4 q = {1, 1, 1.5, 1}; q /= length(q); v@P = sigma(qmultiply(f_tau(tau, v@P.x, v@P.y), q)); or just use file from Matt Ebb a long time ago http://mattebb.com/blog/
28. 2 points

## Worms

Hi, I'm trying to recreate this very cool tyflow setup in Houdini. In the description he explain's how he is using dynamic PhysX rigidbodies and using attraction forces to move them, looks really cool. I've had a go with some success using the crowd system in Houdini with RBDs and a pop attract. Hip files here worms_03_GC.hip worms_05_GC.hip worms03.avi worms05.avi The idea works but I can't get a nice behaviour using the pop attract, has anyone got any ideas what might work better with the particle forces? Thanks worms_05_GC.hip
29. 2 points

## How can I control blending of two shapes, using an attribute?

I usually just build my own blendshape node with a simple VEX code using lerp() - just one line. https://hdbp.io/BjGNeLeB Easy to change to what you need: https://hdbp.io/e0iS3H5J I find it easier than Aizatulin approach, since you can control the attribute distribution completely by the nodes you want.
30. 2 points

## How can I control blending of two shapes, using an attribute?

Hi, you have two objects and want to use another object, to control the blend amount between both objects? Is this what you are looking for? blend_inside_controlGeo.hipnc
31. 2 points

## New project : UEFA Champions League

Finally, 2 years later... we are now allowed to talk about it. https://www.jordibares.com/post/2018-07-07/champions-league-rebrand/ The text is a bit lame but it is the only we are allowed to use... sorry guys.
32. 2 points

## Procedurally reverse objects

Shoot rays along the normals. If they all end up on the piece they are coming from you know it's inverted. inside_out.hipnc
33. 2 points

## Drive Particles from Point A to Point B

Made you a file to test the method. I don't know if that's what you're looking for. morphParticles.hip
34. 2 points

## vex function find all attribute name

Hi Julien, with addpoint() you can reference an existing point to get all its attributes and group memberships: https://www.sidefx.com/docs/houdini/vex/functions/addpoint.html Also, there is a detail intrinsic, which stores all the point attribute names: s[]@pointattributes = detailintrinsic(0,"pointattributes");
35. 2 points

## How to dynamic remove loop line?

Polyreduce with Continue Reducing within Quality Tolerance and a low value for Tolerance, and [x] Preserve Quads. It will find large quads that approximate your geo, but it's not guaranteed that it will always delete those edges. It's doing the expected result on this kind of geo because by construction, there are large quads because of the extrusion. You can force edges in the output with the Hard Edges list though, depending on your workflow.
36. 2 points

## Particles from particles

I do not think you will want to use it like that (if that is the case, yes it will explode). You can control with a popstream or a popgroup and have a nicer split of the particles, here is an example. ParticleReplicator.hipnc
37. 2 points

The same workflow applies for meshes, too. colorcurve_meshes.hipnc
38. 2 points

@meldrew and check this
39. 2 points

## Keeping RBD pieces from falling off

Hi, try to play with gravity dop and popwrangle dops in the DopNetwork and with timeshift sop in DOP_Import also test.mov Scene01.04_01.hipnc Edited: I've did some correction and re-uploaded the scene.
40. 2 points

## Flip Fluids deforming collision objects

Here is the i@stopped attribute included inside the if statement. I dropped the viscosity threshold, quite a bit, so the fluid would come to a stop quicker. if (@viscosity>3600){ @viscosity = 3600; @v = set(0,0,0); i@stopped = 1; } ap_SimCon1.hiplc
41. 2 points

## Quaternions & Matrices

For the full course, visit : https://cgforge.com/course?courseid=quaternions-matrices In this quick tip, we take a look at a practical example which takes advantage of both quaternion and matrix (and/or Euler) based rotation.
42. 2 points

## Direct Modeling HDA

My quarrel has ended. We found a solution, and Alexey politely took back his harsher words. That was a surprising and nice turnaround in the end.
43. 2 points

## spiderweb incomplete

Just closed your add then added a polypath. Here you go: spider_v02.hipnc (oh and add a fuse after your merge before it goes into the vellum so makes it one object )
44. 2 points

45. 2 points

## Matrices - CG Forge - Quicktip

For more tutorials, check out cgforge.com In this quick tip, I talk about matrices. If you've ever wondered about what a matrix is, and how they can be useful, then you'll love this introduction to the topic. Thanks for watching!
46. 2 points

## Proper Branching Topology

Just stick the branches into the trunk and other branches. You most likely don't need it to be water tight single perfectly modeled object like it might come out of ZBrush. Don't fall into a science-experiment mentality, it's an endless rabbit hole. Just get the pixels out
47. 2 points

## Direct Modeling HDA

Hi Alexey, Last year you said the upgrade from DM1 to DM 2.0 was going to be free, how do current DM users get the new version? thanks
48. 2 points

49. 2 points

## Why is my Color Transfer Offset?

here is an example, I created boxes based on the points, but you can create points from boxes too if you need it that way cut_by_boxes.hip
50. 2 points

## Attribute from map not applying as expected

I had a similar problem that I managed to fix by unlocking my "attribute from map" node and then going to the top right node called "promote_vertex_uvs_to_points". Inside that I changed the promotion method from "average" to "last match" (or "first match"). I'm guessing it has something to do with points along the edge of UV seams having more than one UV co-ordinate, and then something weird happens when it averages the value for all co-ords of that point, I'm guessing it averages over the entire UV area between the co-ords? First or last match probably just chooses the value at the first/last co-ordinate.
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