Welcome to od|forum

Register now to gain access to all of our features. Once registered and logged in, you will be able to contribute to this site by submitting your own content or replying to existing content. You'll be able to customize your profile, receive reputation points as a reward for submitting content, while also communicating with other members via your own private inbox, plus much more! This message will be removed once you have signed in.

Sign in to follow this  
Followers 0
Opticspy

Mantra Render issue to PNG

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,

post-14647-0-23486300-1443995521_thumb.p

Edited by Opticspy

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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?

Share this post


Link to post
Share on other sites

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. 

Share this post


Link to post
Share on other sites

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....

Share this post


Link to post
Share on other sites

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!

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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

 

disableColorSpace.PNG

Edited by acey195

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0