Any suggestions on how I can accoplish this...


I’m working on a project and am trying to achieve an animated scene somewhat like the link above. I need to have a beam that illuminates the ocean floor, and the beam needs to leave a “trail”, so that once the ocean floor has been illuminated, it stays illuminated.

I have a couple of half baked ideas on how to accomplish this. But I’m sure someone here has a better idea. As always, any help would be greatly appreciated!




maybe extrude some geometry along a curve just above the ground and make the extrusion match the light beam. Then render out an ambient occlusion pass sequence from just the ground and the exruded object and composit that on top of the ground.

if you invert the bright- and dark color in the ambient occlusion shader and lower the settings to 1 sample an 0 spread it renders very fast and you get a “solid” white line.


Quick thought-Do it in post with the aid of an animated primitive that acts as the mask of the lit ocean floor layer.

So you render out the ocean floor twice- and use this animated shape that follows the edge of the beam as a reveal. I’d try first to use an animated slice with a grid that is connected to the and parallel to the beam via parenting or a constraint.

How complex is the ocean floor etc.? Can you give us anymore details as to the complexity of the scene/render?


It’s relatively easy to achieve with an animated weightmap.
Look up LM weightmap tools (by La Maison) if you need some pre-baked tools to help you with it.

The long story made short is that you can look up weight and vertex colour maps in the rendertree, and both can be animated relatively easily (if the surface isn’t too complex) by bounding boxes and enclosing primitives. You can then look-up the weightmap in the rendertree to weight the mixing between an illuminated shading and a darker one.

Without the specifics it’s hard to give more or more pertinent advice, but if you’re not too far from the reference picture it’s EZmode stuff.


Thinking outside the Lightwave box! :thumbsup:


Hi guys. Thanks for all the suggestions, though I have to admit, if there’s one aspect of 3D that I’m somewhat clueless about, it’s rendering.

While waiting for responses, I went ahead and created my own solution. It’s no perfect, but it seems to be working.

I just created a giant grid above my scene that had a “beam” shape cut out of it. I then pointed an infinate light straight down and made it inclusive to just the grid, and the ocean floor. Then I animated the grid to move across the scene and reveal more light.

It works pretty well, but I’ve been unable to get the “glowing” strip at the bottom of the sonar to work properly. The ocean floor is bumpy, which screws up the “glow” effect if I try to use that.



I explored most of the ideas we posted here about how to accomplish this, and while I’m almost certain that I didn’t do each version proper justice, and that there are probably a million other ways not posted here on how to do it, I came up with a simple and easy to use version that hasn’t been talked about here yet- at least in full.

You can read my ramblings about it, see some little demo videos, and download the simple hackish scene here:

I’d love to know what I’ve done wrong or what could have been a better option because I know one exsists. Come on you TDs- time to get out the can of felixble and powerful woopass and show us how it’s really done!

Still I think for our man/lady here doing the sonar demo this method is just fine.



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