Sunday, August 21, 2011

Another day, another dozen renders

I believe I can slightly prematurely say I have finished the chapter on Global Illumination. I am finishing up the last few renders, and need to add the summary, but other than that I'm done. Barring revisions (always something isn't there?). This chapter was a beefy 50 or so pages and full of more recent technique which required additional research on my part. Keeping up with technology is an ongoing job, as everybody knows it is a moving target. Luckily for me I'm endlessly fascinated with the subject. I believe there is far more lighting trivia in my head than is good for a person. I should be a fraction as well informed about world events and I'd be a much more interesting conversationalist. Ah well.
Here are some lovely renders using reflection occlusion. Most digital lighters know of ambient occlusion, but reflection occlusion is lesser known, so for those who haven't used it here's an introduction.

Two digital renders. On the left is has no reflection occlusion, on the right has reflection occlusion
That little frog again. he's alot of fun ;)

Here's a tip for the day:
When you are trying to solve a problem: Divide and Conquer!
Narrow it down so you can isolate where the problem is. It is much easier to find a needle in a small handful of hay than in a haystack.
To isolate the problem in a digital render, I often make whatever I'm working on some crazy color so I can see it better. My favorite crazy color for debugging is magenta. Here's an image with the ambient occlusion turned to magenta so I can see it better.

Egg render on the left (lighting by Howard Ross, a student in my lighting class. nice eggs, Howard!), egg render being debugged for occlusion on the right (did anyone think those were real eggs?)

Friday, August 19, 2011

More thoughts on Global Illumination

As I sit and wait for another really long render, I am looking for things to keep me productive. Not sure if the blog qualifies, but what the heck.What to do when waiting for a render. General  summary: Keep busy.
My thought on Global Illumination is "Wow that looks nice!" Followed by "Good lord, it is only how far along?" as I wait for a full res, high quality render. While the big studios have just recently gotten to the point where they are using GI most of the time, this is made possible by two things the average Jane like me doesn't have. One is a gigantic renderfarm (Pixar ramped up to 12,500 cores for Cars 2), and the other is proprietary software that makes things go a bit faster which they do not always share with me and you.

Tip of the Day:
On another track, as a professor I often see ambient occlusion used incorrectly. So here's the correct and incorrect ways to implement it. Ambient occlusion is often multiplied with the beauty pass in the composite. This is incorrect. It actually should only affect the ambient contribution  or else you will end up with overdone occlusion in the areas of direct light.
Occlusion multiplied by the entire render leads to too much occlusion. Notice the dark shadow in front of the clown.

In this example using render passes, you need three passes: Occlusion, ambient only, and direct light only. Occlusion should affect ambient only, then be added to the direct light for better results.

Wednesday, August 17, 2011

Starting a blog

At the suggestion of a friend, I am starting a blog about the writing of my book Illuminated Pixels: the Why, What, and How of Digital Lighting. I must admit I'm not much of a blogger, but here goes. I am in the final stretch of the book, and it has been a very long haul. I first thought to write a digital lighting book at least 5 years ago and began dabbling with chapters and outlines. i didn't really get down to business until about 2 years ago, but still - it's been a long time coming. I've had to update material as I go along, as the area of technique is always changing. Especially in the past about 5 years things have really changed in high end digital lighting. However, the fundamentals remain the same. And the book is about fundamentals as much as anything else.

Right now, however, the chapters are about technique, and I'm rendering images showing various examples of image based lighting. And gees do they take a long time. i decided to make them smaller ;)

Render Tip of the day: Reducing your render by 1/2 the size saves 3/4 the time. So my 8 inch wide, 40 minute a frame just became a 4 inch wide, 10 minute a frame render.

Image of the Day:
Simple scene (thanks to the students at SCAD-Atlanta for the frog and fly models) rendered with a single environment light and full global illumination.