Hi,
I’m having my first try of LuxBlender for the weekend comp…
The scene is set up with a sun lamp and a mesh made to be a light. The two lights are virtually on opposite sides of the focus models.
The problem is that the lamp doesn’t appear to be casting any shadow, as you can see here…
Can anyone, ahem, shed any light please?
er… Here’s a snap-shop of some details, ask for any more…
p.s. The selected item is the mesh light…
p.p.s. Yes, the normals of the light mesh are pointing down…
I’ve been playing with light groups so that I can adjust the lights whilst it’s rendering. Only problem is the render isn’t updating, so I have to see the saved image (only saved once every two mins).
By altering the gain of the downlight to 1.2, I can see the second shadows. So naturally I went back to blender and bumped up the gain there, from 5 to 15, then 25, now 100. There was no discernible difference.
Upon further reading the gain slider in actual Lux only affects how it’s layer is mixed and not the actual gain. So in reality it’s a totally different control.
Ideas?
You probably need to increase the gain of the lamp a lot, possibly even more than 1000 as the sun is quite strong. To double check that gain is indeed the problem, try rendering without the sun.
The effect of raising the gain in the exporter or in the LuxRender interface is different in the way that doing it in LuxRender’s interface will lower the rendering efficiency significantly. The reason for this is that the program will look at the original brightness of a light source to decide how to distribute calculation power between the different light sources. Other than that, the effect should be the same so you could try and see what happens if you switch off the sun lightgroup in LuxRender.
Not to mention adjusting the post-burn. Now I say this apprehensively, but, even though the Blender lamps work (with one exception in Lux) it’s highly recommended to not use them (as I recall reading). The principle behind it is that Lux operates as an actual emission across the surface and it effectively chokes that math by emitting from a single point, more so when you want more scattered light. All the same, I recommend using all mesh (maybe spots, which I do use often) to create the lighting you want. Turn the sun into a sphere mesh and you will have better results.
Also, if you are looking for a higher spectrum scatter, build your scene in a “room” just as it would be real world. Lux calculates what’s coming off the surfaces, so even with a sun in open “space”… it won’t scatter back to light the subject. This also speeds render exposure time.
As for gains, unless I specifically know a severe power difference, I leave them default and adjust them post process.
Cheers AbelAbel,
I am currently trying a render with the sun and sky gains being set at 0.1. I’ve upped the lights wattage to 320, the gains max is 100. And because it’s dark i’ve lowered the gamma to 0.2 in Lux.
I’d set the tone mapping as follows (a basic from http://www.blenderguru.com/create-a-realistic-kitchen-part-2-of-2/):
I’m not too sure on these settings, even though I did a photography course many years ago. Anyway, i’m going to see how they will effect it…
p.s. If I turn off the sun and sky groups, it is fairly dark but the shadows are there…
Quandtum, Cheers.
Yes, I have built a full room.
There is a single sun lamp for the environment and a mesh light (which i’m trying to keep small, supposedly improves caustics (which it does!!!), http://www.luxrender.net/wiki/index.php?title=Creating_Beautiful_Caustics).
However I am trying to avoid any post processing, lux or otherwise (just using for testing, even though it’s different than setting in Blender).
Thinking about it I used to use iso 400 film for interiors. Reading some posts about wedding photography and they suggest 1600.
In actual Lux there’s pre-sets right up to 6400, in LuxBlender it only goes up to 1000.
… Trying more variations now… whilst waiting for the legacy… http://www.youtube.com/watch?v=a1IpPpB3iWI
Sorta getting some results by setting the lamp to:
… and the Sky and Sun gains set to 0.8
Ah, I see what you’re really going for now (will be nice effect). I was thinking you were looking for more of an AO-esque shadow. Now I see why you specifically want a sun rather then faking the sun with a light setup. My appologies, you’re way ahead of me there (I haven’t done much consideration with caustics), though you’ve peaked my curiosity now (and I love playing with Lux, it’s the only way I get the laundry done). If you still need help too, hollar, I can attempt to setup simulation here.
In LuxRender, the sun is not actually a point light. Unless you’re after really soft shadows, there’s no reason to avoid it.
Well there should be quite a severe power difference between a light bulb and the sun.
In reality on a sunny day, it may be impossible to tell if a street light is switched on or off as the sun is so much brighter. If the balance is still off, don’t be afraid to set the sun gain to for example 0.001.
While avoiding light groups modifications is wise, tone mapping settings are not post processing unless you consider a hdr image your final output. One could say they are as much post processing as adjusting the shutter time or developing film on a real camera are post processing.
I’ve never really looked into HDRI before (hmmm, some good Sunday reading). In general with my photographs I only run them through auto levels (maybe with a little tweak).
With LuxRender as far I understand tweaking the tone mapping settings is ‘safe’, however when I find something I am comfortable with I then reflect them within LuxBlender.
Here’s my current result. It now has two lights and a sun.
I’m a bit ill at mo, so who knows what i’ll get done today. I do want to get a spectrum out of those glasses though (but best results seems to be at lower overall light levels).
But no matter what, I will reserve a future competition entry using for a full room scene and Lux. This is still my first play…
p.s. I saw a rainbow last evening, is that possible with lux, say using a particle emitter?
I suppose it is, but the questions are how long it will take and how to approach the modeling. I don’t know the answer to either; posting the question on the LuxRender forum might be a good idea.
Slightly off topic…
I set off a probable final render about an hour ago (now 1.5 hours). The only difference to it’s previous render was to double the image size. However i’m now getting lot’s of highlights and more keep coming…
My question is (since this is my first render of this size), will it all smooth out with time or is there something else I should do?
NB. This size is only 1600 x 800
… and it’s still getting worse more white spots with black outlines!
That’s bad news, those won’t go away. Are you by any chance on Windows? If so, please get a recent build instead of 0.7 as a bug that looks similar to this got fixed recently.
The other possibility is that something is wrong with your material setup. If you don’t mind sharing the scene, it would be good to upload it on the support section on the LuxRender forum.
It’s gonna have to wait…
This machine runs Fedora 12. I’ve got everything setup, but to build I need to install an opencl sdk, which i’m going to have to leave till tomorrow night…
I say this, but i’m moving on it…
Cheers