cgcris Posted March 26, 2015 Share Posted March 26, 2015 As the title says, I rendering though a glass sphere and need the alpha of what's inside... any ideas? Thanks! Quote Link to comment Share on other sites More sharing options...
mestela Posted March 31, 2015 Share Posted March 31, 2015 Cribbed notes from these 2 places: http://houdini.dreamerzstudio.net/?page_id=67 http://forums.odforce.net/topic/12291-raytracing-and-alpha-question/ To get this: Probably not quite right, but should be enough to get you started. refract_alpha.hip Looks like Dany Bittel's layered PBR shader does this automatically and has a bunch of other cool features, probably worth getting it if you need a good material base to work with. http://forums.odforce.net/topic/18353-pbr-all-purpose-layered-shader/ Quote Link to comment Share on other sites More sharing options...
cgcris Posted March 31, 2015 Author Share Posted March 31, 2015 Hi Matt, Thanks a lot for your reply, will look into this options! Also got this lead from the sidefx forum, passing info between shaders: http://www.sidefx.com/docs/houdini14.0/vex/functions/trace#idm47446624006848 Quote Link to comment Share on other sites More sharing options...
fathom Posted April 3, 2015 Share Posted April 3, 2015 calling "trace()" will let you easily grab the Alpha or Opacity (instead of just the color). what's more, if you tag the rays as "primary" rays, then "Matte" and "Phantom" will still operate appropriately, which is kinda neat (ie, the trace rays won't hit Phantom objects and Matte will knock holes in the resulting alpha). it's a great way to collect reflections and refractions (with mattes) for later compositing. Quote Link to comment Share on other sites More sharing options...
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