September 6 2009
While working on my Occlusionist plug-in I stumbled across an interesting side-effect of generating ambient occlusion in screen-space: It’s possible to achieve computationally expensive global illumination effects such as color bouncing in the same way!
And what’s best… it comes pretty much for free!
Screen-space color bouncing (right)
As it turns out, when processing ambient occlusion the
Occlusionist is already doing everything required to achieve color-bouncing, so it’s simple enough to call the source image’s color and bounce that around to simulate a nice final gather or global illumination effect right in
After Effects.
The overhead is somewhere around 10 – 20%, which is totally acceptable when you consider that true 3D global illumination effects generally take much, much longer to render.
Having access to screen-space ambient occlusion plus color bouncing right within After Effects will certainly make for some very interesting effects and opens a whole new world of possibilities!
September 1 2009
The Occlusionist is a spin-off of my Adobe After Effects plug-in Normality and is used to generate screen space ambient occlusion (SSAO) and global illumination effects.
So what’s ambient occlusion you ask? Basically, AO is an approximative global illumination method that checks to see whether any given point on a surface is occluded by other surfaces.
Right… now what does
that mean?! Well, objects that are close to each other block some of the ambient light which is cast by the sky or the surrounding room, for example. So the more ambient light is blocked in this way, the darker the surface becomes. This creates a nice shadowing effect which can be similar to true global illumination methods.
The effect is commonly used in 3D productions where true GI techniques such as Final Gather or radiosity would be too computationally expensive, whereas AO is comparatively quick to render and does not require a complicated setup.
It’s an incredibly useful tool to give your renders more depth and a more realistic appearance.
Usage
The Occlusionist requires a depth and a normal pass to do its thing. Once you’ve gotten those rendered out of your 3D program of choice it’s pretty straightforward to create ambient occlusion effects: Apply the Occlusionist plug-in, calibrate your normal– and depth pass and there you go — clean (or noisy, as you wish) occlusion effects right in After Effects.
This makes for a wonderful addition to your Normality workflow.
Although AO is fairly quick to render in any modern 3D ray-tracing engine, some of us prefer even faster methods — the reason I developed Normality in the first place!
I hope to get the Occlusionist plug-in close to real-time speed, which will probably require either making it multi-threaded or having it run directly on the GPU.
WIP
At this point the Occlusionist is a work in progress: It’s not at all optimized and requires too many samples to achieve pleasing, noise-free results, which in turn makes the render time a bit too long for my taste. 3 – 5 seconds per frame may be a dream come true from a 3D renderer’s point of view, but in comp that just doesn’t quite cut it.
In the coming weeks I’ll try to get the render-times to a level more on par with what After Effects users are comfortable with.
April 22 2009
The look and some effects of the expensive Final Gather technique can be simulated with this light shader. PhysicalSkylight uses an HDRI environment map to light the scene and renders fast ambient occlusion shadows from the direction of the light source.
To accurately simulate a final gather look it is necessary to pre-filter the environment map in an external program using a technique called spherical harmonics.
Unlike true final gather, this technique does not introduce unwanted flicker in animation sequences, but it also does not handle secondary bounces.
Usage
This light shader is best suited for outdoor environments such as overcast daylight on a cloudy day. It is not intended for interior renders but may be used for directional ambient occlusion.
PhysicalSkylight can also be used to bring out small details in a scene without creating the dirty look of a multiplied occlusion pass.
April 2 2009
Reverse ambient occlusion is a novel technique that can be used to improve texture painting or to mask specific areas in a layered shader.
This shader works like an ambient occlusion shader but offers the option to sample the interior of objects as well as the outside.
Usage
minRAO may be used to generate areas of wear, dust and dirt for example to help create wear and dirt around edges and corners. It works well as an alpha mask with baked textures or in combination with the minLayer shader.
