Topics

1

[Max] I need help! / Corona Color Correct - Formula behind it?

« on: 2020-01-10, 11:28:56 »

I've been working with the colorCorrect tool and am trying to understand the math going on when I adjust hue, saturation and brightness.  For example, I have a purple input color:

CoronaColor HSV = (190, 255, 84)

And I want use colorCorrect to increase the brightness by 0.5.  Is there a formula to calculate the resulting output color in HSV (a brighter purple)?

Appreciate the help.

2

[Max] I need help! / Possible to mimic CoronaMTL fresnel curve?

« on: 2019-12-20, 06:50:42 »

I have a standard CoronaMTL with reflection level set to 1.0 and the Fresnel IOR set to the default 1.52.  I applied it to a sphere and rendered with no lights or reflections in the scene.  This is what the CShading_RawComponent--Reflection element looks like.

I'm trying to recreate the RawComponent output above in a separate CTexmap element but can't get a perfect match.  When I create a generic fresnel falloff map with 1.52 IOR and plug into CTexmap I get a notably different output in the VFB (see below).

Am I doing something wrong here or are max's built-in fresnel curve and corona's internal fresnel curve different from one another?  I dug up this thread from a few years ago that seems to indicate they are indeed different.  If so, is there a way to get the Corona curve into a CTexmap element?

https://forum.corona-renderer.com/index.php?topic=8214.0

3

[Max] I need help! / Is it possible to "deconstruct" a CoronaLayeredMtl in post production?

« on: 2019-03-10, 07:49:40 »

Hi all,

As the subject implies, I am trying to deconstruct a CoronaLayeredMtl and reassemble it in post-production (using Photoshop):

- The material I'm working with is a carpaint, it consists of a base coat and a clear coat
- The base coat and the clear coat are each layers in a CoronaLayeredMtl I created
- The mask that "mixes" the two layers is a falloff (fresnel)
- I'm using 32-bit uncompressed EXR's for all renders

My question is whether it is possible to render the base coat and clear coat separately and then combine them in post?  If so:

- How do I output the fresnel falloff in 3ds Max to an exr that can be used as a mask between the layers in Photoshop
- What would be the proper "blending mode" to use in Photoshop?  Normal, linear dodge or something else?

Appreciate the help.

Nate

4

[Max] I need help! / CoronaColor - Formula to convert 32-bit Linear RGB to sRGB 8-bit?

« on: 2017-07-10, 00:41:21 »

Hi all,

Wanted to see if someone could help me, I'm trying to write a mathematical formula which converts an RGB value from 32-bit linear to sRGB 8-bit (and vice versa).  In essence, I just want to mimic what the CoronaColor picker does with its color preview.  Using the color below as an example, I'd like to know how Corona converts the linear (56,244,6) into the 8-bit preview (128,250,46).  Is there a formula I can use to do this conversion?  I wasn't able to find anything in the help files on this subject.

5

[Max] General Discussion / VFB Tone Mapping as Render Element for compositing?

« on: 2017-06-08, 14:25:54 »

Love v1.6 so far thanks for all the work!  Been using the VFB tone mapping controls/curves more and more these days but still need to use LWF for compositing.  Most of the time, I end up trying to mimic Corona's tone mapping in photoshop, but would be great if they were their own render element I could layer on in post.

Still a noob with tone mapping, LUTs, etc. so apologies if this is a really dumb question.  I saw bloom/glare had been added as a render element so I wondered if the other controls from the VFB Post tab could be as well.

6

[Max] I need help! / Artifacts around edges of render selected region

« on: 2017-01-08, 20:25:47 »

Hi,

Working on a script that utilizes the "render selected" functionality in Corona and having some issues getting a clean output.  I put together an illustration below:

 

In image A I rendered the whole scene.  The outer circle has a green material and the inner has a gray.  In image B, I changed the material of the inner circle to green and enabled "render selected" in Corona.  As you can see the output image has some artifacts where the inner and outer circles meet (looks like some of the old gray material is still showing through).



In image C I rerendered the whole image (ie "render selected" turned off) with both the inner and outer circles in green and the artifacts disappear.  Am I doing something wrong or is this just a limitation of the "render selected" functionality?  I am using Corona v1.3 if that is relevant.  I thought the issue might get better with additional passes but that doesn't really help.

7

[Max] I need help! / Splitting Render into Smaller Tiles (3ds Max) - Best Practices?

« on: 2015-09-01, 14:31:43 »

Hi all, new to Corona and loving the product so far.  I’m currently working on a maxscript that breaks a render into smaller tiles, and have come across some minor issues:

• To test my script, I am taking a simple 768x512 pixel rendering and splitting it into six 256x256 pixel tiles (3 columns x 2 rows)
• I am using the #crop functionality in maxscript and saving the output as .tifs
• My script calculates the “top left” and “bottom right” pixel coordinates for each tile as illustrated below:

The script works as expected, except when I try to reassemble the tiles I get noticeable seams (see below in red box):
 

 
So apparently this is a pretty common problem with distributed rendering, most sources say the solution is to create a 10-20 pixel overlap between tiles that gets trimmed away in post.  I've done that and although it helps a little, it doesn’t completely eliminate the problem, even with a 128 pixel overlap:
 
20 Pixel Overlap:
 

128 Pixel Overlap:

 
Curious whether anyone knows a workaround to this problem.  I’ve tried some minor tweaking to the render settings but still getting the same issues.  Is it better to use #region vs. #crop?  Are there render region controls native to the Corona VFB that work better for splitting the image?  Appreciate any feedback!
 
Some additional background:

• I’m using Alpha v6 right now (but will definitely buy the most recent version if I can get this working)
• I’m just rendering on one machine at the moment (this isn’t a backburner related issue)
• Using bucket rendering, quality settings are generally set very low at this point
• As mentioned, I’m saving the images as TIFs so I don’t think the seams are the result of compression artifacts