GOBO Lighting in A:M

[detbear]

I'm not sure if I can make it to the Q&A tomorrow, but I need to create Sea floor caustics. In other apps, this is done by what is known as a "Gobo" light.

 

Basically you use a spotlight{"Kleig") and place an animated image map in front of it. The image is set to only let light pass through the light areas....much like A:M's Transparency Map type. The animated image is pre-created with turbulent combiners to get a Caustic look.

 

When the light shines through the image, it makes caustics on the surfaces below.

 

Has anyone done this in A:M?

Can it be done like this in A:M?

[robcat2075]

I believe the process is to drag an image onto a light.

[robcat2075]

It seems you can also drag a Material onto a light, which would save you the intermediate step of rendering your caustic pattern into an image sequence.

 

[Rodney]

Okay, that is very cool.

I don't think I've ever tried using a material on a light before.

Nice.

[fae_alba]

Hey I needed that on my Papa Bear short for that underwater look.

[detbear]

That is AWESOME RC.

 

Seems like I now recall that you can add mats to lights. I guess you can also animate the Mat too..correct?

 

Anyone have a good Caustic pattern Animation?? That would be helpful for the community also. I think it would bennefit to have a few in

the library to use.

[robcat2075]

That is AWESOME RC.

 

Seems like I now recall that you can add mats to lights. I guess you can also animate the Mat too..correct?

 

I've been experimenting with this. I can animate setting on the material and it renders as expected...

 

CausticVolTest000.mov

 

 

 

 

but.... when i save and reload the PRJ the animation doesn't work anymore. Seems to be a problem even back to v17

 

 

 

For now the workaround may be that you have to save your PRJ BEFORE you add the material to the light.

 

Load the PRJ, add the material and redo your animation settings, which you have written down before hand.

 

Of course, Netrender isn't an option with this scenario.

 

A bug report may be in order.

[John Bigboote]

Very cool... we used to call these kind of things a 'kukalora' when I was doing things on a stage... (kookoo-laura) As I remember- we had lots of fun with that word. You could similarly do it the way we would do it back then... animated a sequence in AE or A:M with an alpha channel- place it in front of a klieg light as a layer... out of view of the camera. Then you could play with the kliegs settings for how 'in-focus' you want your effect. For underwater waves... I would go into After-Effects and use the turbulent noise effect- altho what Rob has going looks pretty danged good!

[Fuchur]

You should not use a 3d-layer for that... keep in mind that A:M needs to calculate that as a "3d-object" all the time, while having it as a mask for the light will very likely result in lower rendertimes...

(I never tested it... this is just a guess...)

See you

*Fuchur*

[robcat2075]

I gave Matt's practical light version a try with a Material on a small grid in front of a light

 

It does work. You'll need to set Transparency somewhere between 0 and 100% for the two Parameters of the Combiner and experiment with color combinations. If you want to use a colored light instead of a colored material, you will need to set the light color in the Chor

 

You'll also need to set your Kleig light to Ray-Traced. Z-Buffered won't properly cast partial shadows through partially transparent objects.

 

There probably is a small render time hit in having to use a Ray-traced light but it was fairly speedy none-the-less and this method doesn't lose the material's animation when the PRJ is saved.

 

 

[detbear]

Also, there needs to be a way to get rid of the "Spotlight" shadowing. The caustics need to have even lighting over a larger area rather than the circular (Spot)effect.

[robcat2075]

You can move the Kleig Light farther away so it lights your whole scene.

 

We did that for TWO so we could use faster-rendering z-buffered shadows instead of ray-traced Sun lights.

 

If you make its cone angle small and move it far away it will appear like the parallel rays of a Sun light.