The Add_pixel_to_viewport_accumulator(X, Y, Z, row_coord, column_coord) Webpage

As we said near the end of the previous webpage, it is very likely that when we project all the hyperspace tunnel pixels down into the viewport, many of the pixels will project into the same viewport pixel. If we don't do anything about this, then each time another tunnel pixel projects down into a viewport pixel, it will overwrite the previous pixel color with another color. A better solution would be to keep track of all, or at least some selected number, of the tunnel pixels and their associated colors that project down into each viewport pixel. Then when all tunnel pixels have been projected into the viewport, we just go through all the tunnel pixels that projected into each particular viewport pixel, and we average all these pixel colors together to form the resulting average color for each viewport pixel. This is exactly what the Viewport Accumulator Array, i.e. VAA, does for us.

The VAA is a 3D array of integers. The width of the array is the number of pixels in the viewport, namely 800. The height of the array is 340 and this is also the height of the viewport in pixels. The depth of the VAA is 200. A depth of 200 means that we will keep track of a maximum of 200 tunnel pixels that project into each of the viewport pixels. If more than 200 tunnel pixels project into any viewport pixel, then we just ignore them. Within each integer cell of the 3D array, we will keep track of two pieces of information, those being the texture map row and column of each tunnel pixel that projected into this viewport pixel. We can put these two pieces of information into a single integer value by using bit fields. See the below diagram.