Chaos Corona Forum

Chaos Corona for 3ds Max => [Max] I need help! => Topic started by: jjduncs on 2014-09-17, 15:02:55

Title: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-09-17, 15:02:55

I'm after some help with fitting an object into a photo backplate.

Ive got the backplate setup in my viewport and in the environment map etc. It is showing up fine in the render.

I then set up the ground plane with a shadow catch mtl with the backplate plugged in, this seemed to work too.

The issue I am having is the exposure of the objects. I can't seem to change the exposure of the scene without affecting the exposure of the backplate. Also, is there a way to use photographic exposure without  affecting the exposure of the backplate?

I don't know why but my corona sun and coronasky intensity values have to be at 0.1 to get okay looking results.

If some one could talk me through the proper method for setting this type of thing up, with a backplate and a corona sun + sky for lighting, it would be hugely helpful! thanks.

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-09-17, 15:05:22

Here is how i have it looking.

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: juang3d on 2014-09-17, 15:16:00

Have you seen the videos here?:

https://forum.corona-renderer.com/index.php/topic,3995.0.html

I think your problem is commented there.

Cheers.

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-09-17, 15:41:07

Thanks for that! I tried searching 'shadow catcher' and 'backplate' etc etc but couldnt find a relevant thread.

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-09-17, 16:09:10

Part 3 covered it well. Just needed to use a CoronaMapOutput.

Thanks again.

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-09-17, 17:46:36

got it sorted.

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: juang3d on 2014-09-17, 20:22:40

Great! Glad you solved it :D

Cheers.

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-10-12, 16:53:36

On doing some more renders with this scene, I've come across another problem.

Im getting more fireflies on my 3d elements when I use the "For compositing" mode in the shadowcatch material.
 
I'm using the direct visibility over ride as black so it should all be the same.

When I re-enable the backplate map in visibility over ride and turn shadow catch mtl back to always solid the fireflies are drastically reduced.

Anyone else experienced this?

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-10-12, 17:04:17

both after 7 passes

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: juang3d on 2014-10-12, 23:35:51

In your already comp pic you don't have reflectivity in the floor, but you have it in the black render, maybe this has something to do with this, but I haven't experienced the problem before.

Cheers.

Edit: sorry it's not reflectivity, it was a mistake, but why can I see part of your backplate in the black render?

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-10-13, 04:25:46

Yeah those two images are renderered with exact same setttings for everything except with the shadow catch mtl turned to for 'forcompositing' mode and the direct visibility turned to black (bitmap unchecked) for the left one.

I think the backplate is showing up a little because of GI from the facade and surroundings.. with the alpha map mask this mostly goes away.

Still having issues with more fireflies in compositing mode though!

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: Ludvik Koutny on 2014-10-13, 12:58:40

Quite strange. Do you use HDcache by any chance?

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-10-13, 17:27:10

Yeah this is PT + HD Cache.

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: Ludvik Koutny on 2014-10-13, 19:06:45

Could you try if same artifact appears with PT+PT? Just to be sure...

Title: Re: CoronaShadowCatcherMTL + Backplate Help
Post by: jjduncs on 2014-10-15, 12:38:10

Yep PT + PT seems to fix this.

Is this normal for the Alpha Mode to effect the noise etc with HD cache?