Opticspy Posted October 4, 2015 Share Posted October 4, 2015 (edited) I have possibly not so a common a task done from Houdini FX and Mantra, I create various VFX via Pyro or Particle System inside Houdini and need to render IMAGE Frame in PNG format with Alpha Channel. I admit im not a grand master however I'm hoping someone in this forum has successfully done this. The issue is color, when i render PNG (RGBA_Alpha) SRGB, the image generates some black color that does not exist, and a very muted version of original view seen in mantra. I have provided a before and after image to help explain what is happening better, Below is frame 70, this issue seems specific to PNG only or more specifically when alpha channel is applied, without alpha channel i will get good result. If I render EXR and or TGA, bring into to composting software like NUKE or After Effects, same issue when converted to PNG. in the example below i added a black ground in bottom image to show how muted the image becomes, Im wondering... does anything special need to be done to Houdini channel before rendering to a PNG? thanks in advance, Edited October 4, 2015 by Opticspy Quote Link to comment Share on other sites More sharing options...
Guest tar Posted October 5, 2015 Share Posted October 5, 2015 Not sure exactly except that anything bar EXR is usually a problem. MPlay has a 'Convert to Image Format's Colorspace' which the MantraRop doesn't afaik. Quote Link to comment Share on other sites More sharing options...
Opticspy Posted October 5, 2015 Author Share Posted October 5, 2015 Hi Marty, thanks for your response, I was hoping someone knew how to render a PNG cleanly from Houdini, there is no way to do this? Quote Link to comment Share on other sites More sharing options...
Guest tar Posted October 5, 2015 Share Posted October 5, 2015 Perhaps there may be but we only see issues with PNG, not successes posted up on the boards PNG is widely not used as it's not a professional format. Quote Link to comment Share on other sites More sharing options...
Opticspy Posted October 5, 2015 Author Share Posted October 5, 2015 I know tradiiotnally in movies projects where size is no limit, EXR is the best, however in this case I need the size advantage PNG can offer, I just would have thought since Houdini FX offers to save PNG format they would have some way to render the image correctly.... another interesting thing, my sample could not show it because of the black background i assigned, but trail of smoke changed color to greys and blacks which was not even part of the original file, when saving as TIFF or TGA for example... the image shows none of these colors. Im wondering maybe some other program like Maya or Max can export PNG better.... Quote Link to comment Share on other sites More sharing options...
Guest tar Posted October 5, 2015 Share Posted October 5, 2015 Perhaps - the solution out of MPlay is the only way I've seen to do this through testing for other people. In vfx we throw around HD;s like nothing else - try Deep frames they can be hundreds of MB per frame! Quote Link to comment Share on other sites More sharing options...
carlo_c Posted October 5, 2015 Share Posted October 5, 2015 I'd check to see what your alpha channel is doing if it looks correct without an alpha, it might help to throw up the PNG too Quote Link to comment Share on other sites More sharing options...
Opticspy Posted October 5, 2015 Author Share Posted October 5, 2015 yes if saved without alpha, it looks good, i think semi transparent pixels are getting replaced by grey and black, even if they are meant to have the yellows and oranges..... I guess its some kind of fall off. Quote Link to comment Share on other sites More sharing options...
Guido Zanni Posted October 5, 2015 Share Posted October 5, 2015 attach the HIP Quote Link to comment Share on other sites More sharing options...
Atom Posted October 5, 2015 Share Posted October 5, 2015 When I first started with Houdini I had the same problem, giving upon PNG. But you can still render successfully to PNG. There are some tips here: https://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=35133&highlight= Quote Link to comment Share on other sites More sharing options...
SreckoM Posted October 6, 2015 Share Posted October 6, 2015 Maybe it is premulitply issue? Quote Link to comment Share on other sites More sharing options...
yesyes Posted October 7, 2015 Share Posted October 7, 2015 render to exr then convert to png in composite Quote Link to comment Share on other sites More sharing options...
acey195 Posted July 12, 2017 Share Posted July 12, 2017 (edited) reviving this topic for a moment... Is there still no way of disabling the toggle in the Mantra Output node? In openGL it works just fine, but that doesn't run via command-line yet. When using custom format, or for 8bit data textures, where you need linear interpolation, this would be very appreciated... edit: or is THE solution to render the file at gamma 1/2.2.. which does seem like a hack to me Edited July 12, 2017 by acey195 Quote Link to comment Share on other sites More sharing options...
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