Houdini Isn't Scary - Part 5: Rendering

Welcome back to Part 5 of Houdini Isn't Scary, this part is the continuation of the donut rendering part. We are finishing off the render settings needed for rendering our donut. This means that we're covering ROPs as well as Motion blur, Velocity blur and how to actually save out an image from Houdini.

When we ran our sprinkles through the DOP network, we generated velocity. That velocity can be used to blur our sprinkles as they fall. To do that, we need to activate our motion blur in two places: Firstly, on the sprinkles object. And, secondly, on the render node in our /out network.

Next we activate depth of field. Depth of field is the blurring that you notice in an image when things fall in and out of focus. At a larger scale, depth of field is less noticeable but as we move to smaller scales, the amount of blurring increases. For the most part the blurring is controlled by the scale and by the f-stop. If you'd like to understand f-stop in real life (and by association in Houdini), here's a great article:
https://photographylife.com/f-stop

Finally, we need to render our image out. To do this, we need to tackle the intimidating 'Output Picture' on our Mantra ROP. The default expression is usually alright to use but if you're iterating and want to control the filenames, it is best to understand a bit of hscript. $HIP, is simply the folder that your file is saved in. /RENDER could be anything, it could be /images or /donutImageFiles. It is a sub-folder of $HIP. $HIPNAME is the name of the file. Usually your files might be named something like 'DonutProjectFile.hip'. $HIPNAME would then take 'DonutProjectFile' as a value. $OS is the name of the render node ('mantra_ipr' in this case) but that makes it useful if you have multiple render nodes and want each one to output something different. $F4 is a alteration of $F. $F is the number of the frame you're on. $F4 just means add some padding to the number with 4 zeroes (eg. 0001, 0002, 0003 etc.). And then we have the filetype. By default it is .exr. However, it can be set to .jpg, .png, .img etc. I do recommend learning to work with .exr though. Here is some useful information on filetypes:
https://www.pluralsight.com/blog/film...

That's it, Part 5 is done and so are the basics. We are going to create something awesome in the upcoming parts so I'd suggest subscribing if you've liked the content so far; you won't want to miss this.

Thanks for watching, if you need the file from Part 4, you can get it here:
https://www.dropbox.com/s/54x15ushhwy...

Part 5's file is here as well if you need it:
https://www.dropbox.com/s/irjciber2v9...


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