Lights! Cycles! Action!

Support Lighting and Rendering
1

Hi Gang! :smiley:
Soooo, after some weeks of grousing about Cycles, not having a GPU, and wondering if I was the lone voice of reason in a squall of Cycles crazies…
I got a GPU, figured out that the reason Cycles and everything else kept crashing was because the wires for the new powersupply and graphics card the CompUsa guy installed were mashing up against the GPU fans…
and started working on my newest animated short in Cycles. And I’ve FALLEN IN LOVE WITH IT!
Maybe it will take time for a lot of us who are so used to BI to adapt, but adapt we shall. Because it is DEFINITELY worth it.
I’ve never created such realistic renders before. Cycles is going to completely change my entire perspective on animation and rendering. Already has. I’m never going back to the Old Way. Yes. Cyles MAY BE the Dark Side. But Cycles certainly is “Quicker. Easier. More seductive. Once you start down the Dark Path, forever will it dominate your destiny. CONSUME YOU IT WILL!” So, I’m 100% ready to be consumed by Cycles! :eek:

At this point, my only question for the Cycles Wonks is:
what’s the deal with LIGHTING?!
Unlike some other rendering engines, Cycles makes quick and gorgeous work of Global Illumination. It’s easy, it’s real. I’d have no problem (I think…) with simply using GI to light everything I do for now on. Probably will.
However, part of the artistry and responsibility of a film director is to make sure the lighting expresses mood, pulls the eye, turns a dull scene into a vivid living reality, even makes it more real than real. A film student I once knew who specialized in lighting told me that he felt filmmaking is ALL about lighting. I tend to agree with him, to a large extent.
So, let’s make a big deal about lighting in Cycles! :smiley:

Alright. So, my major question is about the old Blender lights. You know, your old standby, the Spot, and his friends Point, Area, Sun, Hemi et al. Well, I can’t get them to do very much in Cycles other than roll over and play dead.
The other approach is meshlighting, using a mesh plane or sphere or cube, what have you, and sticking an emission texture on it. It works, but you end up getting squirrely with mesh normals, and rotating them around to try to get them to point in just the right way at your scene. Of course Cycles makes this sort of thing VERY interactive, and that’s one of the beauty parts of Cycles.
However, the plane meshlight I put into my scene seems to be doing some odd things with fireflies on my props. Delete the meshlight and POOF! the fireflies suddenly disappear without a trace when I have some GI going…

Anyway, just wanted to touch base and see what the experienced Cycles users had to say. Lighting is an important topic, and Cycles is the future of Blender. Get used to it.
And power up the batteries for your red lightsabers. You’re gonna need 'em.

2

TL,DR:

That is feature, fireflies are good, quick smooth old-scool phong gradients are bad!

Cycles use path tracer (unbiased, but slowest from all unbiased algorithms) with nice trick “direct lighting”. It “cheat” a bit to get result faster, but not always correct. Transparent shadows for example, shadow probe ignore any alpha, see cycles/intern/cycles/kernel/kernel_path.h :160).

                                if(direct_emission(kg, &sd, light_t, light_o, light_u, light_v, &light_ray, &light_L)) {
                                        /* trace shadow ray */
                                        if(!scene_intersect(kg, &light_ray, true, &isect))
                                                L += throughput*light_L;
                                }

You can turn off that trick by commenting some lines, and get pure unbiased “path tracer”, but render time to get compared quality image increased dramatically, most time you see just fireflies, that is feature, not bug. Those fireflies go away after long waiting, and you get really correct image, with transparent shadows, all that unbiased coolness.

That is good for big companies with renderfarms, but unacceptible for interactive preview window on single box.

If you ask me, i am prefere some meta-slider at render option, “biasness” with sane defult, when it set to 1 then use pure good old Phong ray tracer with 2-3 max reflection ray depth, 5-6 refraction (to allow cool glass-on-tablescened withowt tweaking ) for artists, and if set to 0 use hardcore decent quality MLT tracer for all other.

Maybe it is possible to make general MLT render and tweak direct and backward paths to reduce code size, for example MLT with 1 eye ray depth and same “direct light” looks very close to BI tracer. The problem, who can make all that, but it is another story.