video5.mpg

27.3.2010 Sobel filters Just before I went to bed last night I read about the so called sobel operator which is often used in finding edges for images. The filter basically gives every pixel a number that is the larger the larger the difference between it and its adjacent pixels. This was an easy algorithm to implement. Running the filter against image data would be a bad idea though. For this I had extracted the shape of the surface (normals and depth values) from the partially rendered image. When I run the sobel filter against this data I get large values wherever there is a jump in the shape. But this gives equally sized edges everywhere and to be honest it looks quite bad. Luckily if the jump in the shape is large the sobel filter value goes far above 1 which is the maximum. If I blur the these values I get these get wider cool looking edges. 28.3.2010 HDR rendering Today I read some papers about High Dynamic Range filtering. Google for "HDR" and check the images you get, they’re very cool. So the idea is that when normally every pixel you render has to be between 0 and 1, which leaves the image look flat. The sun can be dozens of times brigther than an inside room. They simply don't fit in the same range. To fix this the scene is rendered first without this cramping restriction. Only after everything has been rendered, to a texture, the pixel values are then downscaled from like 0...20 to 0...1 by some curve. Finding a curve that produces good results is not so easy ...

Channel: YouTube Video Length: 35s Date Found: Sun, Mar 28 2010 9:17 AM Category: Technology Date Produced: Sun, Mar 28 2010 8:56 AM View Count: 0