When you turn this puppy on, the whole world will look different. But, what happens when you tinker with SSAO? Smash them together, and what you wind up talking about is the occlusion of ambient lighting, or the blocking of your surrounding lighting. Plants that would otherwise be illuminated on all sides suddenly have shadows opposite the direction of the light.
Though ambient occlusion is pretty common these days, back in the early s and well before that , it was nonexistent. Gaming worlds were brightly lit, no matter how many 3D objects were on screen. Then came the game that all future video games were compared to — Crysis. In , Crytek released a title that taxed GPUs around the world.
Part of the reason why Crysis was so resource-hungry was because of ambient occlusion. Before we start - note that SSAO is a general acronym for "screen space ambient occlusion". The name encompasses all of the various ambient occlusion AO techniques and their variants that work in screen space it means that they obtain all information at runtime from data that are rendered on the computer screen and into related memory buffers. We have based our approach on a horizon-based technique called GTAO that was introduced in a paper by Activision.
The ambient occlusion AO name part means that we evaluate how much of incoming light predominantly sky light, but sometimes the computed occlusion gets applied also to other lights gets occluded at a particular place in the game world.
A specific level of ambient occlusion at a particular place affects lighting computations and creates shadowed areas in creases, holes, and other 'complex' places. So instead of baking static information which would also take a lot of time and storage space given the scale of our world map , we want to compute it on the fly, in run-time.
That way we can compute it also for interaction with vehicles, opening bridges, animated objects, and so on. There is a catch though. For such a computation approach, we only have data that are visible on the screen recall "screen space" , so once some part of the game world gets out of the visible frame, it can't be used for occlusion evaluation.
This limitation creates various artifacts such as disappearing occlusion on a wall originally caused by an object that just got behind the edge of the screen and thus became invisible not just for you but also for the algorithm, so it ceased to contribute to occlusion computation. Ok, now we know what to evaluate ambient occlusion and we know what data we have what we see on screen. Its cost depends purely on screen resolution and SSAO parameters and does not depend on scene complexity as true AO would.
However, the approximation tends to introduce artifacts. For example, objects that are outside of the screen do not contribute to occlusion and the amount of occlusion is dependent on viewing angle and camera position. Note that SSAO is quite expensive in terms of processing time and generally should only be used on high-end graphics cards.
Once the texture is generated, the remainder of the SSAO effect is performed on the graphics card. This effect requires a graphics card that supports Shader Model 3 and depth textures. Even so, many were able to enjoy the realistic visuals that the game had to offer. Like any other technology, ambient occlusion has improved greatly over time. Below are some different types of it.
Different graphics cards and their architectures and rendering technologies contributed to various ambient occlusion enhancements. Instead, SSAO looks at the pixels around the element and their depth, which makes CPU usage more efficient , while introducing dynamic rendering to make the ambient light more realistic.
Instead of focusing on the entire screen, SSAO measures ambient occlusion in pixel depth at a part of the screen. However, graphics card performance and video game demands have increased over time, which brought new techniques. It does so by considering the ambient light and the environment instead of just the pixels.
0コメント