What's quicker, omni or rectangular lights?

[thomthom]

Re: What's quicker, omni or rectangular lights?

I'm posting some of the test renders I did while experimenting with LC. I prefer images over text, guessing more people do as well.

Rendered with physical camera, light source is sky with one rectangular light inside the box.

First of is a series of four renders with different subdivision. You can see that there's hardly any difference in the resulting image except render time. (first image is missing sky as I forgot to remove the alpha in VFB)
IR (low quality) + LC





Next is a render with same settings as the third image, except this time the rectangular light is stored with IR. Notice the render time difference.

[justin1023]

Re: What's quicker, omni or rectangular lights?

Are there any consequences to storing the light with IR?

Justin

[sheldon]

Re: What's quicker, omni or rectangular lights?

Where did you get that 3D person from. Looks pretty good.
Thanks

[thomthom]

Re: What's quicker, omni or rectangular lights?

Where did you get that 3D person from. Looks pretty good.
Thanks

From the Warehouse. Reallusion iClone got a few. Ok for mid-distance shots. http://sketchup.google.com/3dwarehou...84495214113323

[dalomar_cg]

Re: What's quicker, omni or rectangular lights?

Are there any consequences to storing the light with IR?

There aren't really any consequences when you have a high quality IR map solution. At a lower quality level you might not get things like shadows as sharp as you'd like, but since most low quality settings are for tests I'd say it wouldn't matter too much.

[AcesHigh]

Re: What's quicker, omni or rectangular lights?

quite interesting topic.

my problem is that I have this 130 floors skyscraper, and I have put a few dozen rectangular lights at each floor. The objective was to add realism to the scene, by allowing exterior shots to show the fluorescent light inside, through the glass.

kinda like in this real photo


needless to say, with such a high number of floors, and dozens of rec lights per floor, even with very low subdivs (only 2) per light, and storing Irradiance Maps, the render times are still loooong...

btw, its important to notice I do not want to illuminate the building interior in these external DAYLIGHT shoots... what I want is to make the fluorescent lightbulbs to be visible through the windows! Only that...

[AcesHigh]

Re: What's quicker, omni or rectangular lights?

another example of what I am trying to achieve

Ventura Corporate Towers, Rio de Janeiro

[thomthom]

Re: What's quicker, omni or rectangular lights?

Not sure how to work around that. You could set up one floor. Make it into a component. Then copy it to the rest of the floor. Keeping it hidden until you do your final (slow) render...

[AcesHigh]

Re: What's quicker, omni or rectangular lights?

@Thomthom: its already a component, multiplied several times per floor. Since some floors are also components (after all, I have about 130 of them! ), lights placed inside a floor component were also multiplied along the building, and lights are on a layer apart.


I set everything to really low levels, and still it takes a long time to render.

I have some theories on how to improve render times...

1 - separate the lights of the buildings by layers... floor 1-20 (layer LIGHT1-20), floor 21-40 (LIGHT21-40) and so on. So I can disable most light layers when doing exterior renderins showing only a part of the building

2 - since my objective IS NOT illumination... and apparently, no matter how badly you setup the rectangular light, the whole area still shines well through the glass, I could create a few huge rectangular lights per floor, and create geometry OVER it to simulate the many different fluorescent light spots

3 - the original post by Dalomar only confronted rectangular vs point lights. I wonder how material lights work. Their end result, when they are the main light source always look quite terrible, which leads me to believe they have the worst simpler calculations of all. Thus, maybe they would be the best to be used for this specific task?


here is a test render with normal number of rectangular lights (dozens per floor, in one layer, which is turned on)
i cancelled the render after 1 hour and a half. Pass 4 had begun, but it was SO SLOW that I mentally calculated it would take at least 5 more hours to finish pass 4, which was much slower than other passes.

[thomthom]

Re: What's quicker, omni or rectangular lights?

Emitting materials aren't known to be quick. But you could try.

I think the lights which you see in our LC pass might not be so bright when the final render pass is done.

[dalomar_cg]

Re: What's quicker, omni or rectangular lights?

The problem that's being run into here is that your lights are coming from behind glass, which means that every time all your lights are sampled, there's a certain amount of reflection/refraction that's involved in figuring out the end result. This is what's causing the massive slowdown, not the lights themselves.

In this case, because you're not using the lights for a true illumination purpose, I would recommend using a simple light emitting materal. Since light materials really aren't sampled in the same manner as lights, this should help speed things up a bit. As for the material itself, keep it a relatively low intensity. You don't want to make the lights super bright as that will likely introduce artifacts. Just bright enough to get the appearance you want, nothing more. Test from the "bottom up" to find exactly where that intensity is.