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Looking for an old thread about compositing
show user profile  owtdor
As many of you know, I am in the process of creating some animations of oil rigs in the ocean. I have run up against several issues and solved some of them. I still am having a major problem though.
I am creating the water with Dreamscape, which uses the scanline renderer. The oil rig was built to be rendered in Mental Ray. Because of this, I am not able to render both elements in a single image. I will have to do a water pass and rig pass.

My question is this: How do I render out the oil rig so that the alpha channel shows the appropriate amount as the waves mover over it? (I will comp them in After Effects)

I know there was a thread here with same issue being addressed, but I can't seem to find it.

read 522 times
2/11/2012 10:51:49 PM (last edit: 2/11/2012 10:51:49 PM)
show user profile  owtdor
Wow, nothing?

read 498 times
2/12/2012 10:42:35 PM (last edit: 2/12/2012 10:42:35 PM)
show user profile  owtdor
Maybe I should explain a little better?

I need to know how to composite my water surface with my oil rig so that when I overlay the oil rig layer on top of the water layer, it will show only what is above the water. I want the underwater parts that are covered by the water to be blocked out when I render. The end result being that the oil rig looks like it is bobbing about in the ocean.

Some specs - Water will be rendered to TGA or PNG vie the default scanline renderer
Oil rig will be rendered to TGA or PNG with Mental Ray
Background will be a static overcast sky image. (Maybe a sky dome pass)

Time is limited so any help is appreciated!

read 476 times
2/13/2012 5:16:26 AM (last edit: 2/13/2012 5:16:26 AM)
show user profile  donvella
Can you explain, or show an image of something similar? To me it sounds like you already know what you have to do but cant find the buttons. Place bg on bottom layer, then building, then ocean, yeh? Just make sure you dont save out your ocean with any opacity or refractivity. The top half (sky should be the only alpha part)

... Come on man, why cant you render it using mental ray water, it has some beautiful defaults. Shouldnt take more then 5 minutes to create a nice water in max if your having that much trouble matching the two.

read 471 times
2/13/2012 5:49:58 AM (last edit: 2/13/2012 5:53:32 AM)
show user profile  owtdor
It's not as simple as just layering the items. I need the rig to appear to be "in" the water, not behind it. There will be 45 foot waves pounding it so it is not a simple plane. Every frame will be vastly different. On some frames the front left leg might be 1/4 covered, and then 100 frames later it might be 3/4 covered.
Basically I want to render the rig but use the water as a mask on the alpha, without rendering the water itself.There was a thread on something similar to this in the past 6 months, but I can't find it.

read 462 times
2/13/2012 7:59:21 AM (last edit: 2/13/2012 7:59:21 AM)
show user profile  donvella
Fair enough, hopefully someone will share before you run out of time. I would like to read it myself considering this doesnt sound very complicated, unless you want the rig to react to the waves etc? Why cant you use 2/3 layers of water, just comp it add some dof to give it some depth and your done?Can you show example of the final you want to achieve?

read 458 times
2/13/2012 8:12:48 AM (last edit: 2/13/2012 8:12:48 AM)
show user profile  Bolteon
you'll need to find a way to render them at the same time... they need to exist in the same space if you want one to refract the other.

-Marko Mandaric

read 447 times
2/13/2012 9:20:38 AM (last edit: 2/13/2012 9:20:38 AM)
show user profile  owtdor
Bolts - I already thought about that and it turns out since there is no real direct sunlight (overcast) there is not much, if any reflection onto the rig. At the scale of the scene, the water does not need to refract since it actually appears to be opaque when the waves get this high.

I know this is possible, I just need to figure it out. If it was not possible, then people could not render different objects in separate passes.

read 435 times
2/13/2012 4:18:43 PM (last edit: 2/13/2012 4:21:15 PM)
show user profile  Joey Parker Jr.
If you have this. But you want the water and rig rendered separately.

The alpha channel from saving as png.

Here's the default water in vray.

Change setting to this:

And you will get this:

And alpha like this:

So what you need is to turn the water into a matte/shadow object in Mental ray so that
the water act like the mask for the rig. Now you need a mental ray person to tell you how.
I'm positive there is a mental ray equivalent.
If I totally missed your point just ignore this.
 photo 2012-sig_small3_zpsbd114b69.png

read 420 times
2/13/2012 5:00:42 PM (last edit: 2/13/2012 5:00:42 PM)
show user profile  owtdor
That is EXACTLY what I needed! Thank you so much! (well, except for the VRay part anyway)


read 418 times
2/13/2012 5:02:09 PM (last edit: 2/13/2012 5:02:56 PM)
show user profile  Joey Parker Jr.
You're very welcome :)
I just tried this with the mental ray matte/shadow/reflection material and it works.
 photo 2012-sig_small3_zpsbd114b69.png

read 410 times
2/13/2012 5:12:08 PM (last edit: 2/13/2012 5:12:08 PM)
show user profile  donvella
lol matte the object, i got thrown with the term 'composite'. good work.

read 307 times
2/13/2012 11:57:56 PM (last edit: 2/13/2012 11:57:56 PM)
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