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Lighting Effects.

Oct 1, 2014, 18:46
Post: #1
Lighting Effects.
I'm wondering how the position of the light in Lighting Effects relates to the position of the cursor on the canvas? So far I have been having to guess the rough area where I want the light to be. The X,Y and Z position on the light tab are nothing like the readings I get for the cursor.
Any pointers for this would be great as I would like to be able to position the light with more accuracy.
Cheers.

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Oct 2, 2014, 12:54 (This post was last modified: Oct 2, 2014 12:55 by rich2005.)
Post: #2
RE: Lighting Effects.
@Caz
Interesting question. The lighting plugin goes back to Gimp 1, I think. The source code might give some insight but not for me.
Trial and observation equally screwed. For a point light source, if you set z=0 then the top left seems to be 0,0 and the bottom right corner 1,1 but other procedures indicate a 1.41 position so maybe root 2 is in there somewhere.

Since you are using linux you might be interested in this stand-alone application. UrbanLightscape - free for linux
http://www.indii.org/software/urbanlightscape/
You can get the source code there, from memory not difficult to compile. Looks like there is a ppa for 'buntu/mint users
http://linuxg.net/how-to-install-urban-l...pear-os-8/

What it looks like - a quick before and after http://i.imgur.com/O2Vq3R5.jpg

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Oct 2, 2014, 17:07
Post: #3
RE: Lighting Effects.
Thanks, Ofnuts and Rich. I just had a quick play around and the Z axis does control the distance of the light as it should. Still baffled as to how to find an exact location for the light though. Does look as if this is an element of Gimp that could do with an update.
I will give the UrbanLightscape app a go and see how I get on.
Did try a selection that was 40 percent smaller than the image to see if I could spot any clues as to how the cursor would relate to LE setting, nothing jumping out at me yet. I will keep experimenting and post any results here.

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Oct 4, 2014, 10:42
Post: #4
RE: Lighting Effects.
Found out a few settings that might be of help to others.
It seems that if the x and y axis are set to .50 and the z axis is left at 1.00 this will set the point light to the centre of any canvas size.
If the z axis is left at 1.00 the following x,y settings place the light at various locations along the canvas border.

Far right centre
x -2.00
y .50

Far left centre
x 3.00
y .50

Centre bottom
x .50
y 3.00

Centre top
x .50
y -2.00

Adding a plus or minus value of 2.5 to the centre starting position of .50, to either the x or y axis, places the light at various locations along the canvas border.

Top left corner
x 3.00
y -2.00

Top right corner
x -2.00
y -2.00

The light direction always appears to be pointed to the centre of the canvas.

Shouldn't be too difficult to set up a series of guide at 10% intervals, x and y axis, for more accurate placement of the light.
Best to find where the light needs to be placed, then on a new black layer place a small white dot, align the light to this dot then switch to the layer that requires the lighting effect and let the filter run.

[Image: DjIVv.png?1]

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