Motion Blur

Motion Blur in today’s games

Today’s HD games demand the use of a lot special effects, which range from HDR, to bloom. All of these effects are done simply like a filter over the game, done as post processing after the scene is rendered.

 One of the more special effects is motion blur, done mainly to first/third person camera games, or any where the player can dynamically move the camera . The main reason is to make the camera movements more blurry, and in a way “more realistic”. Though the effect is most defiantly unique, it also is annoying, as a lot of people prefer to turn it off when playing their game. 

 Heres some examples of motion blur in action

 

Crysis 3 + motion blur 

MW2's trailer using motion blur

 Blurring in games 

The Blurring technique is done in countless games, is quite simple in concept. We start by mixing the color values of each pixel with the ones nearby.  Generally blurring is done with every pixel around it, in a 1 pixel radius, resulting in an area of 3x3 pixels per run. We average out this mixed color, and apply it to the pixels in the area.

 With this we can blur the sharpest pictures. Not only it be used for just for special effects, but it is also an important step used to help create a bloom effect.

How motion blur is done

To go any deeper, we would have to know about frame buffers, which are where the scene is rendered to prior to displaying them. Here in frame buffers we have many different values which we can pass in, and others we may not want to pass in. These may be the color of the scene, or the depth of the objects in the scene. 

For Motion blur, we need the depth buffer as input to a pixel shader program in order to generate the scene's general velocity. This shader program will compute the world positions for each pixel by using the depth value, stored in the depth buffer, and with the current frame's view-projection matrix. Once we determine the world position at that pixel, we can transform it by using the previous frame's view-projection matrix. Then we can compute the difference in the viewport position between the current frame and the previous frame in order to generate the per-pixel velocity values. A motion blur effect can then be achieved by using this velocity vector as a direction to gather multiple samples across the frame buffer, averaging them out along the way to generate a blur.

For more on how to implement motion blur click here 

From all of this we can see how different the game can look after see it with motion blur. With motion blur, some people argue that it is a neccessity to have in future games. Not only does it give the sence of realism but it also allows for game developers to create less detailed games, while maintaining a great look. This is because motion blur warps our perspective, not allowing up to carefully examine objects in the scene. Whether motion blur is seen more in the future, or not, we cannot deny how important these "special effects" are in today's games.