View Full Version : fakeGI softlight

03 March 2003, 12:24 AM
now i know that there is already a tuturial about fakeGI (the pdf one)
but i'm wondering since i'm getting mixed resultss with it.
how do most people do it.
there fakeGI

since most of the time i get no where near any results that i would like.

this would be the way i now do it.

spotlight a few instances above the target.
uvsphere at 16,16 division.
then offcourse the parent, duplivert,rot,switch normals.
spotBI as by the book around 600'ish
since short i'm also watching a eye on my clipend and clipstart :P
and for the rest i mostly put my energy around .050 and the color to a light blend of yellowish or broken white.

so please enlighten me, what is the beter way, what are the points one must pay attension too or not forget to set.

03 March 2003, 02:00 AM
Just a couple of things I found useful with fake GI set-ups.

Try turning the spot to halo by turning on the halo button but don't increase halo int yet. This will add a soft mist like look. Then try increasing halo intensity to see the effect. If you want real fog effect try setting halostep to 1. You will have to play with these depending on what effect you want.

Another thing to do to some GI type scenes is add a couple of shadow only lamps for shadows without effecting the light in the scene.

03 March 2003, 02:35 AM
You can also try using Eeshlo's IBL script.

it's a bit old, so it might not work with 2.26, but it works perfectly in 2.23.
It's a very complex script, but the information packaged with it is very complete and should get you started.


03 March 2003, 03:26 AM
Umm, okay. I do this all the time. First, you want to use the icosphere. The uvsphere won't give you good convergence with your spot lamps. Start out with an icosphere of divison level 2.

Make a spot lamp. I usually keep the default angle of 45 degrees. I set the edge falloff the whole way up (1). Start with a map size of 512, leave softness and samples alone, and crank the bias down to around 0.4.

Parent this lamp to the icosphere. Duplivert the icosphere. Enter editmode, select all, reverse normals.

Select your lamp, then rotate it in the various views until all of the dupliverted spots converge. You can now adjust your clip start and clip end, as well as the shadow distance values for the lamp, so that you are covering all of the objects that you want.

I get great results with this.

For even more fun, select a couple of the faces on the icosphere and subdivide them a few times. This will give a nice, soft directional component to the lighting.

Oh, and if it were me, I'd avoid the halo button on the spots unless you really need it.

Good luck!

If you're still having trouble after this, link to an image and a blend file so we can look at it.

03 March 2003, 06:28 PM
I usually keep the default angle of 45 degrees

hmm, I usually set this to about 100 or more, with a distance of about 120 or more.

crank the bias down to around 0.4

I never touch the Bias setting at all.

Select your lamp, then rotate it in the various views until all of the dupliverted spots converge.

If you ADD>LAMP in top view, (Num Pad 7), then you do not have to do this step. Just parent the lamp to the Icosphere and then duplivert it in top view.

Not that any of my ways are better, but that is how I do it, typically, and I also get great results. I usually set my samples up a lot higher than 512 as well.


03 March 2003, 08:01 PM
well i tried a few things but still with little success :(

here's a picture of 'the best' i could get.
clickable 1600x1400(224KB) (

and here's the blend file.
fakeGI.blend (39KB) (

03 March 2003, 09:30 PM
Well, I am at work here, so no Blender :thumbsdow , and thus, I can not play with your blend file.

But here are some suggestions based on the settings in your image:

1) Set the SpotSI to about 120
2) Set the ClipEnd to around 125 or higher
3) You will likely have to increase the Distance to greater than 5 after you do the above to get the lamp to shine onto the sphere. PLay with it until you get something you like.
4) To really fake the GI, you can also place a lamp directly under the sphere with the same colour setting as the floor plane to fake a reflected light colour on the bottom of the sphere. Make this really low in power though, cause you just want a faint hint of this colour to show.

That should do it for you.


03 March 2003, 10:01 PM
I looked at your blend file. I was able to get decent results with the following modifications: samples at 3; shadow map size to 1024; distance to 20. The big difference, though, was that I did a subdivide on the icosphere, upping the number of lamps (of course, I had to reduce lamp strength to .03).

That said, your test scene isn't really the hottest one in the world for this technique. This way of doing things is good at faking GI on models with lots of ins and outs, ridges and troughs, nested objects, etc.

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