The animation tutorial shows how to use $F inside the Node options but not inside actual VEX code. Houdini provides a way to access global variables such as $ F, $FF, $T, $FPS, $PI, $E, $HOME and so on. Parameters created this way will appear by default with a slider. The addition of this parameter has been done in the “ Creating Geometry From Scratch” tutorial. We now summarise the most important details to take away. A golden source can be found here on the Houdini help site. In Houdini we distinguish different types of parameters that we want to clarify here. You can always open up the Parameter Interface and reorder your parameters.Click here to get to find a link to the Guided Houdini Files. In contrast to creating the parameter first then writing the function to link the parameters together. You write your function first then the parameter is created. What fun!Īlso, I could have eliminated the float variable and just had one line of code but this way it’s cleaner. Now you can go ahead and click on the button and like magic, the spare parameter will be created underneath the VEX editor window or whatever that thing is called. You would of course name it in a way to indicate what the value is actually doing. So we refactor the code like the following:įloat mult_value = += * = I passed the chf function an arbitrary string. In this case, we will be using the chf function since the value is a float. We know we have to use our channel functions. ![]() Instead of going through the whole “Open the Parameter Interface, blah, blah, blah…”, all you have to do is click on that image of a tube with a hotdog coming out of it.īut wait! It won’t work just yet. This is where that little thingamajig comes into the picture. However, wouldn’t it be better to be able to keyframe or have interactive control of the mult_value with say a slider control instead of it being a hard coded value? Of course! So I drop down my good old Wrangle node and type in the VEX expression:įloat mult_value = += * = enough. Remember velocity and color are vectors, so this is why I am able to assign to It’s just an arbitrary example to demonstrate. I’m also coloring the particles based on velocity. Then multiple it by some value to speed or slow them down. Let’s say we want to add noise to the velocity of the particles and we pass in the particle’s age as an argument. As an example, I have this glorious sphere that is emitting particles and some added force for award winning style points. When you’re in a POP Wrangle or Attribute Wrangle for example, you may do the same thing to change the value of a multiplier. Not a big deal but if you don’t want to miss that episode of The Fall Guy on TV, time is of the essence. You have to open the Parameter Interface for the node and create parameter types, set the name and label at the minimum, then link them with other parameters using the channel functions. If you have used Cinema 4D, then think User Data and linking the stuff up with Xpresso, Python, etc. You then access those custom parameter values with expressions. If you’re learning Houdini, you probably already came across the nifty bit about being able to add your own custom parameters to a node’s user interface. ![]() Anyways, after thorough research* I figured out what it actually does. The tooltip was not helping me and in hindsight, I’m embarrassed to admit it was sort of obvious. Since it was nagging me, I looked in the help files for the POP Wrangle but I couldn’t find any mention of the button.
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