Tuesday, 7 July 2015

Huabanliuyu refinement: Lighting the opera house.

    It hs been several days since the last post and I would like to finally present some progress. Above is the result of some tweaking with background buildings to get a more convincing-looking metropolis in the background. The other large change is the deeoplemt of a river groundscape which is at a higher elevation to the buildings. While this may lose the feeling of height from the scene, I had done so because I felt it was extremely important to get a 3D environment as I had cut corners during the project in order to save time.
    I mentioned in a previous post that I had gotten a render time down to 15 minutes per frame for the scene. Because the opera house was the most well-lit of all the buildings in the scene, I decided that I should render it seperately from everything else. However during the ensuing rendering sequence the rendering times climbed to half an hour for each frame, which I felt was unacceptable and eventually warranted further investigation in how i could save time.

    After two days of rendering I looked into streamlining the opera house further. I changed what the lights illuminated so that the computer was not trying to calculate any unneeded illumination. It was then I discovered that at some point during the building of the scene, I had linked the ambient occlusion node to the transparancy factor of the opera house's main platform, which is where I believe a lot of the render time was going. After tweaking the light connections and getting rid of the transparency conection (setting it to zero but I had to tone down the specular rolloff and eccentricity) the 30 minute render times dropped to 10 quite promptly. This dramatically upped the number of frames I could make in an hour from 2 to 6

    I was worried the slow render times would take me off track but now that I have only 60 of 250 frames to go, I might be able to get the opera house part of the sequence rendered by the end of the afternoon.

     First render test using the background shader technique I used for Infiltrate Exploit Spread hit a snag. As can be seen, the buildings appeared to use Maya's background colour (which I changed to sky blue during development) as shadows.

     First test I tried to fix the problem was to set the backgroudn colour back to black, but this only succeeded i ndarkening the surface shadows from sky blue to black. And altering the shadow intensity on the background shader to zero did not work either.

     What did work was checking for Maya to ignore rendering the objects themselves, which when performed leaves shadows and reflections floating on an invisible surface. This proved to by the method that worked.

    Depite being mildly transparent (which only showed up when I became more selective with what was illuminated by lights), a black underlayer such as a black panel or the background maya world, hid the transparency somehow without greatly affecting the brightness of the object.

Closer inspection however, reveals that the new opera house is slightly darker with a slightly less intense illumination brought on by the reduced specular intensity to cmpensate for the now-missing transparency factor.


  1. So exciting to see your city coming to renewed life in this way, Mark - and many thanks for all your hard work on our behalf! :)

    1. It was quite fun being given a task that allows me to keep my skills sharp. I'm really looking forward to polishing the end result.