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Mantra Render issue to PNG

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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 by Opticspy
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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.

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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. 

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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....

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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!

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  • 1 year later...

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 :P



Edited by acey195
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