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About 964racer

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    Kevin Smith
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  1. How to set alpha channel with function

    Thank you !! I will take a look at your example...
  2. I have an image file (jpg) with RGB. I would like to create an alpha channel in that image (or I can create one inphotoshop first before I bring the file into houdini) and then set the values in the alpha channel at each pixel to be a function of the RGB values. (say X^2, for example). It looks like the "function" node will allow me to operate on the RGB channels, but then how to I get the output of that into just the alpha channel (as a greyscale) and then set the RGB values to black ? Does the "channel copy" do that for me ? How would I set that up ? Thanks...
  3. Hello-- Still a bit of a Houdini newbie here. Can someone suggest the best techniques to reduce the resolution a quad poly mesh without significantly changing topology ?. In other words, the topology is already good for animation, but I would like to reduce the polygon count and keep the topology as close as possible to the original. Most manual methods show how to create a lower resolution retopologized mesh from dense geometry that has been sculpted in a program like "ZBrush". In this case, I already have a retopologized mesh that has a nice tessellation (quads) for deformation/animation on a skeleton, but I would like to change resolution, preserving quads. Are there any semi-automatic methods for doing this ?
  4. I've been working with Houdini for about 5 months, but I'm still a beginner ! I have an attached an image which came from NASA. This image appeared on their public FB site and I took a screenshot of it. Can anyone suggest techniques in Houdini to recreate an image like this ? My first thoughts (1) model a wire coil to create the basic coiled cyclic structure (2) particle emission along length of wire emitter - maybe wire itself is not rendered. (2) there are also some clouds/volumetric stuff going on. (3) custom shader for particles to get the glowing emission effects towards center (4) star field background - could be just a image comped but could done with points, scattering on a plane or volume. Any thoughts - am I far off ?
  5. Hello, Maybe I'm not finding it, but how do I get a console window on the windows version to display output from my vex code (ex: printf()). Searching previous posts, someone said there is a little window that pops up but I don't see it. I could run Houdini from a shell on windows, but it's not set up to run that way. thanks !!
  6. CGMasterAcademy thumbs up, thumbs down?

    I'm on my third CGMA Houdini class. in my view, the price is expensive relative to others online memberships but it's not that expensive relative to other classes or workshops that go into a significant amount of detail at a professional level. The classes are 8 weeks and I am finding that the instructors are pretty top notch in their area.
  7. Parachute effect

    Hello, I have a effect that requires a parachute. There are potential close-ups of the chute billowing as it is fully deployed as well as the chute collapsing on landing. Th temptation is to try to do this with a full cloth sim .. but...'mmm not sure . If anyone has R+D'd or has any sugs on how to approach Houdini ...even better if there are existing production examples that have been shown ....thanks
  8. node evaluation

    Hello, What are the conditions in which Houdini nodes evaluate ? I recently used a point wrangle node which I used to create geometry on the fly using VEX functions such as addPoint(), addVertex(), addPrim() etc. etc. Thankfully the code is evaluated once in this node for those functions and the size of the node in number of points and primitives stays the same when I press "play". But, if my node is doing something dependent on time, I would expect the node to be re-evaluated if there is any upstream change to the graph (in a node "above"). How does Houdini know the difference between these two cases ? If the node is re-evaluated and there are any geometric creation functions in the body of the VEX code, are they re-evaluated at every step ? Thanks
  9. Translating points procedurally

    Thanks and "hovering" over the labels in the input node, shows the variable name and type. perfect.... I was able to complete my project using some vex code in a point wrangle. Are there any others ways to enter VEX code in Houdini other than in a "wrangle" node or graphically using a VOP node ? Is there a way to use your own editor and create a VEX source file to be referenced by a node ? I watched a recent tutorial on VEX given by the SideFX folks, but it seem to mainly focus on wrangle type nodes for VEX.
  10. Translating points procedurally

    Thanks you ! ...the function, npoints(int) looks like it does it and will help for this value I need , but still looking for where I can find the list of internal attributes I can use like @ptnum etc...
  11. Translating points procedurally

    This is working for me.. Thank you.. but how do I find out what built-in attributes are available from within a pointwrangle node that I can use within the vex expression ? For example, I know from the code examples (shown in the arrow menu) in the code editor box, that certain attributes like @ptnum exist but how do I find out what others are available ? The docs for VEX have a table of some of them, but suppose for example, I would like to know if there is an attribute/variable that contains the total number of points in the group , so in my calculation for the current point, I may want to know how many other points are in the group ? Also, it seems there is a vex function for "ch()", so I would assume that I could get information form other nodes from within a vex script ? That would seem costly in terms of computation for certain operations, but if a @nPoints doesn't exist, I know what the dimensions of the grid is feeding the pointwrangle, so I could derive nPoints from the dimension of the grid (doesn't sound elegant though.) Thanks !!
  12. Translating points procedurally

    Thanks, I will try that with a simple example to see if I can learn how to do that and then apply it to my larger geometry network..thanks
  13. Hello--- I'm relatively new to Houdini. I have a task where I have points which I have extracted from geometry and I would like to translate those points to a location determined by a mathematical function. Let's assume that I can access the points I need by using the "add" node and I have the points from my geometric structure. What is the best way to "loop" through that array of points and translate them to a new location. For example, ignoring Z for the moment, say I just want to translate them in a parabolic shape in 2D using the function y = X^2. (ignore "z" coordinate). What is the easiest way to do this ? I would need to "loop" through various ranges of points in this list and perhaps move them differently, so the function may apply to the first 100 points, but I may want to use a different function for the next 100 etc. so I do need a way to parse through the list. Would you use a point VOB for this ? - or perhaps wrangle it directly in VEX ? - or is there a way to do this in an expression within the node ? Please point me in the right direction, Cheers,