Chaos Corona Forum

Chaos Corona for 3ds Max => [Max] I need help! => Topic started by: aaouviz on 2020-10-20, 10:41:04

Title: Make people 'solid' but 'transparent'
Post by: aaouviz on 2020-10-20, 10:41:04
Sorry for the confusing title, but I'm not sure how else to describe this problem or the solution I'm looking for...

I often render out 'ghosted' white people in sketch renders. I usually do this on a separate pass and photoshop it in later. I'm trying to avoid this step and render the ghosted people into the final beauty pass....

See my attached render - this is a work-in-progress. It's close to the effect I want, but I don't want to see the other side of the people - ie; no arm, just a flat (basically 2d) person. The proper effect is achieved by turning on self-illumination, but if I also want the person 50% transparent, then that's when I get the extra detail I don't want...

Any tips how I might achieve this?

Thanks!
Title: Re: Make people 'solid' but 'transparent'
Post by: maru on 2020-10-20, 15:59:34
Use the Corona Front Back map with one side set to gray and one side set to pure black plugged into the opacity slot.
Title: Re: Make people 'solid' but 'transparent'
Post by: aaouviz on 2020-10-20, 17:01:17
Hi Maru,

Thanks for the suggestion. I did try this. Although that technique does work, per se, it doesn't get me what I want...

The problem is that there is essentially 'more' geometry (front facing to camera) behind the first layer. Take the hand, for example, I don't want it visible behind the body.

I essentially want to create a ghosted silhouette... I can easily create a silhouette (self-illumination) OR I can easily create a ghosted person (opacity), but I'm able to create a ghosted silhouette.

Any tips? Thanks
Title: Re: Make people 'solid' but 'transparent'
Post by: TomG on 2020-10-20, 17:06:42
I think this will have to be done in two steps, as I can't think of a material that says "render only the first time a ray hits this material and not any other time the ray encounters the same material". Might be possible by limiting Max Ray Depth or something, but then you'd ruin the rest of the scene :)

I'd end up going with "render the scene without the figures; enable the figures and use Render Only Masks to get masks for them; use the masks in a post-process to add a transparent silhouette with a solid color and the mask to cut out the figures".
Title: Re: Make people 'solid' but 'transparent'
Post by: aaouviz on 2020-10-20, 17:15:30
Bummer, I was afraid you might say something like this :)

Thanks Tom. I'll go back to my 2-step process
Title: Re: Make people 'solid' but 'transparent'
Post by: burnin on 2020-10-22, 20:10:55
Like here? Only front is visible. But also, no other transparent object is seen behind.

(https://forum.corona-renderer.com/index.php?action=dlattach;topic=31300.0;attach=136140;image)

Description:
Diffuse.
Refraction 90%, IOR= 1.
Ray Switch = invisible in refractions.
Title: Re: Make people 'solid' but 'transparent'
Post by: Jpjapers on 2020-10-23, 10:48:31
Could you make it a milky glass material then make the people themselves not visible in refractions? So you wouldnt see themselves through themselves?
Title: Re: Make people 'solid' but 'transparent'
Post by: burnin on 2020-10-23, 14:09:13
That's the tech demoed above.
But on C4D, where instead of noodling with RaySwitch there's just a click needed on an advanced material option to unchec/disable "Visible in refractions".

Now, added translucency, reflection, refraction, IOR = 1.54, and a bit of roughness.
(https://forum.corona-renderer.com/index.php?action=dlattach;topic=31300.0;attach=136148;image)
Title: Re: Make people 'solid' but 'transparent'
Post by: aaouviz on 2020-10-23, 14:37:05
I appreciate all the replies, guys. Though nothing has quite got the result I wanted. See attached for a more precise versions of what I'm hoping for... a solid silhouette, 50% transparent

I really don't think its possible as a 1-step operation. The attachment was made with 3d people in the scene on a separate texmap pass
Title: Re: Make people 'solid' but 'transparent'
Post by: maru on 2020-10-23, 16:33:19
Quote from: burnin on 2020-10-22, 20:10:55
Like here? Only front is visible. But also, no other transparent object is seen behind.

(https://forum.corona-renderer.com/index.php?action=dlattach;topic=31300.0;attach=136140;image)

Description:
Diffuse.
Refraction 90%, IOR= 1.
Ray Switch = invisible in refractions.

The problem is that if the mannequin bends one elbow or a knee, the two objects will be visible behind each other.
I don't think this can be achieved in Corona.
Title: Re: Make people 'solid' but 'transparent'
Post by: burnin on 2020-10-23, 17:00:47
No, as can be seen all refractive matter behind stays invisible. Which creates a different problem with glass, water and such being invisible behind.

Closest I could get was layering 'XRay' with Light material.

(https://forum.corona-renderer.com/index.php?action=dlattach;topic=31300.0;attach=136171;image)

From experience, the easiest way I did silhouettes, was to 'flatten' the geo (scale to 0 / make it planar) relative to camera and use opacity.
If there's such a script for max, then it's no brainer.