In this video http://area.autodesk.com/blogs/bill/nab_2011_flame_premium_total_control_in... in Part 2 at around 16:20, the demo artist demonstrates very interesting relighting technique in Flame, while inside of Batch. Although there is no Batch in Smoke on a Mac, nevertheless, is it possible to do it in Smoke on a Mac? Or is there a way to achieve it by some other means in Smoke on a Mac? Thanks.
Thank you for your response Grant.
I had looked through all of the tutorial on 3d relighting and I still can't find anything on how to use a luminance key in order to create an occlusion for the lights and flares. All of the tutorials mentioned deal with either images with ready mattes or 3D objects. My question deals with specific ability to do a volumetric relighting with a 2D image, like in the example I originally gave.
Assume your image (with Keyer/luma and a matte made from it)is at 0 in Z.
You need to place a light in the scene and add a lens flare. By default it will also be at 0 in Z. Try and move the light back in Z (-500)
When you do your image will also go black and you might see your lens flare still. Add another light and position it at +500 Z. This should light up the images in your scene. You can now move the light that has the lens flare on it around in the scene and when it go behind you image, it should occlude by the default values.
Yes, I understand that. What I'm trying to find out is how to use the luminance key for cutting the matte to be used as an occlusion layer. How do I do that, how do I position it in 3D, so it's correctly lining up with the main image so it's affecting the occllusion of the lighting, but it is not seen on the screen itself. Would it be possible to see how it's done in some kind of tutorial?
I guess I don't understand what you mean by "Luminance Key". The occlusion is based of of the matte channel of the layer...any and all layers. If you have an object in the media list that has a fill & key the occlusion just works based on the position of the light in Z in relation to the other images in Z in the scene.
So if you had an image of a city skyline, and wanted the lensflare to go behind buildings like the sun rising, then I would take you layer, gmask or key the buildings, place a sky image as the background, or another layer. Position the Sky(if it's a layer)back in Z space, so it's behind the buildings. Add a light & lens flare and position the light between the building layer and the sky layer. If you move the light, the flare will occlude as it goes behind the buildings. This is all done in ACTION.
Even if you image has no matte loaded and you use the Keyer to create a Gmask or some other key, a matte is then created.... and therefore will affect the occlusion.
Maybe if you post a screenshot or something, I might be able to help more.
If you load a standard image into action and go into the keyer to apply a luminance key, this will create a matte for the layer.
Back in the main action compositor, the image will be keyed through. When you place a light behind it with rays, the lighting will respect the matte (alpha) created through the luminance key and the light will shine too.
I used pre-made mattes in my videos just for time saving purposes but it can easily be all done in action.
Hi Grant. Yes, that is exactly my dilemma. When I try to apply the key in action, I end up with only a key layer. It's not hidden by the actual image, that I'm trying to relight. In the Flame demo, that I originally provided, he's talking about having a main image and a copy, which, I guess, he then uses as a luminance key source for the occlusion. That luminance key source then is obscured by the original "unkey'ed" image. This is what I'm not getting...
Here is the example that Bill gives without batch:
1. On the smoke desktop, go into an empty action
2. In The media list, double-click on the B entry for background
3. On the desktop, use the green cursor to select your clip
4. Back in Action, click NEW MEDIA to return to the desktop again
5. Using the red Cursor Tap on the same clip you used as the background. Do the same with the blue cursor.
---- So in action you now have the same image loaded as the background and layer 1
6. In the media list, double-click on the keyer column to enter the keyer for entry 1
7. Set the keyer to Luminance
8. Press F3 to see the Matte view.
9. Adjust the histogram black and white levels to fine tune the matte to isolate your highlights and shadows
10. You may need to invert the matte depending whether you are knocking out the shadows or the highlights from the luminance key.
11. Press F4 to See the result view
12. Exit the keyer back to the action composite.
13. If you move the layer around you should see that you have got a cut out of your image in layer one over the background which is the same image.
--- remember to undo this if you move the layer about
14. Add a light into your scene.
15. Push this light forward in Z-space so if moves behind the camera. This controls your global lighting
16. Create a second light
17. Push this light back in Z-space and it will go behind the layer 1 but never the background
18. Add the Rays node to the second light and make sure that the light connects to the rays node.
19. You should start seeing your rays now.
20. Adjusting the spread of the rays and repositioning it should give you bills effect more or less.
Just for exact settings, go to the setup menu and ensure that shading is enabled and Z-buffer is set to ON.