# bandini

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1. ## Tutorial: Custom F-Curves in Houdini

One seemingly hidden feature in Houdini is the power to attach expressions to time segments between keyframes. In this tutorial, I'm going to show you how to harness this feature to create your own custom interpolation model. We are going to make our own full-featured overshoot f-curve, which will read the incoming channel velocity and create and oscillating motion that exponentially decreases until it arrives at the exiting keyframe value. This tutorial is intermediate to advanced level, with most of it being done in python. Later, I show how convert the code to HScript. Coding experience and familiarity with Houdini is assumed. Houdini Version: 17.5 Level: Intermediate-Advanced Prerequisites: Python/HScript Running Time: 37 Minutes You can buy the tutorial here: https://gum.co/OHlDB
2. ## LearnSquared Houdini Particles

Hi Sebastian, There is a discord channel set up for the class, where you can post questions. You should have received an invite when you signed up. Please check with the L2 team to get you an invite to the channel. In terms of answering questions, I am happy to, when I have the time. Right now, priority help/answers are devoted to students who signed up for the premium track. -Adam
3. ## LearnSquared Houdini Particles

We just released a 4-part particle series I did for LearnSquared: https://www.learnsquared.com/courses/houdini-particles We cover everything from building our own particle solver from scratch, using the built-in Houdini particle POPS, showing how to choreograph and art-direct particle motion, and working through various rendering and instancing strategies.
4. ## Suggestions for overcast ocean

Your photo ref has a lot of color correction on it, by the way. A big part of that look is manipulated in post. Take a look at some reference without all the heavy color correction: First try matching the angle to your reference. Reflections are angle-specific, based on angle of incidence. Work from there. Most of the look of the ocean in your ref is from reflections. Get a HDRI image that matches your look and go from there. Small pinpoints of reflections indicate a small, bright light source or bright spot in your HDRI. So, make sure your HDRI is giving you what you need.
5. ## Direct sss on principled shader

Yeah I just checked it, and you don't get direct SSS in Raytrace or PBR, only indirect SSS. Not sure why. Maybe a question for support at SideFX?
6. ## Direct sss on principled shader

Not in front of Houdini at the moment, so can't confirm, but sometimes image planes are set up for PBR rendering correctly, but don't work with the Raytracer engine (depends on the build). Give PBR a shot and see if it work.
7. ## Merge edit sops?

Check out this command: http://www.sidefx.com/docs/houdini/commands/sopcreateedit It is a little convoluted to use, but it should work for you.
8. ## Python beginner - placing a bone between two locators

There's a lookat matrix that can help you out there. buildLookatRotation(to_node, up_vector=None) → hou.Matrix4 Return a matrix that will rotate this object to look at the specified object. The returned hou.Matrix4 object transforms this object from its current position in world space so that its negative z axis points at the origin of the to_node object. up_vector can either be a hou.Vector3 object or None. If it is None, this method uses an up vector of hou.Vector3(0, 1, 0). You can extract the rotation values from the return value with hou.Matrix4.extractRotates(). You can set an object’s transform with hou.ObjNode.setWorldTransform(). # Set the cam1 object's transform so it points at geo1. cam1 = hou.node("/obj/cam1") lookat_obj = hou.node("/obj/geo1") cam1.setWorldTransform(cam1.buildLookatRotation(lookat_obj)) See also hou.ObjNode.setWorldTransform().

Agencies really like a cool "story" behind the creation of commercials. "We did it in cg" just isn't as sexy as "look at this cool thing we built!"
10. ## Difference between aanoise and Turbulent noise

aanoise has less options, but can take a 4float vector as an input. 4th channel means noise can evolve, rather than just being re-positioned. aanoise ranges from -0.5 - 0.5 Turbulent noise has more noise types. Each noise type has a different output range. This is documented in the help file, as well as the cost for each noise. Unified noise is like an uber version of noise functions. Very slow, but has a lot of great options in it. I typically use aanoise any time I need noise with simple evolution parameters. Unified noise I use for displacements because it looks very natural. Turbulent noise I tend to use in most in-between cases.
11. ## Cloth best practices/Tips n tricks

I did almost exactly what you are looking for using the grain solver. A few gotcha's. When using prefractured pieces, overlapping points will cause explosive forces. You'll need to roll out your own post-sim deformer to match each prefractured piece to the input points. I ended up ensuring matching point counts and ended up with something more like a Maya N-Particle version of a softbody. Not perfect, but worked for my needs. Cloth solver was terrible for what I was trying to do.
12. ## Lighting and Rendering in Mantra Tutorial

Post motion blur on volumes is tricky, and not something I covered. For a tutorial aimed at novice and intermediate users it's a pretty complicated setup (density to SDF conversion, velocity transferring, etc). A little outside of the scope of the tutorial. The other motion blur thing I didn't cover, but I will do a one-off tutorial at some point is how to get proper curved motion blur on particles. (Great for sparks). Linear motion blur on fast-moving chaotic particles is a really easy way to tell a cg render.
13. ## Lighting and Rendering in Mantra Tutorial

Diego, I do a little bit about motion blur, basically describing when and how to use the "Geometry motion blur" option and how to control sampling, as well as talking about how shutter angle affects blur. I also go through the process also of doing a motion blur shader, using getblurP() and showing how to add post motion blur in Nuke. What have your experiences with it at Dneg been? Where did you run into problems?
14. ## Lighting and Rendering in Mantra Tutorial

Hi, I just released a new tutorial about lighting and rendering with Mantra in Houdini. Over 5+ hours of content. Topics include Cameras, Lights, Lighting Setups, Materials and Shaders, Render Settings, and Scene Management. If you don't know where to start with Mantra, or with lighting and rendering, in general, this is a pretty good, comprehensive explanation: http://helloluxx.com/product/houdini-training-learn-jumpstart-vol-8-intro-to-lighting-rendering/ -Adam
15. ## Solver killing alembic animation

If geo is packed, unpack it first so you have access to the deformed points.
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