Lighting a 2D Image without bump?

[therevillsParticipant]

Is it possible?

I’m after a similar effect that be seen on Thimbleweed Park, where I can get a character to walk under a street light:

https://blog.thimbleweedpark.com/quickiepal

(oh I’m getting Forbidden. You submitted too quickly. You may try again in a few seconds. alot!)

[Mark SiblyKeymaster]

Easiest way to do this is probably just to use some 2d blending effect (additive, multiply, both, experiment!) and drawing a yellow ‘spotlight’ image.

[Mark SiblyKeymaster]

I just had a hack around with the simplelight banana, and it is possible for 2d lights to work without normal maps.

Hoever, to make this work, I used a ‘default’ normal of 0,0,1. This is a massive cheat that may or may not look like crap depending on usage.

I’ll leave this hack in (it just allows you to use Image.LoadBump without specifying normal/specular maps) but I think  you’ll get the best results kludging your own 2d blending approach together.

To render lights you probably want to do something like using multiply blending to multiply light * scenes colors (result is lighting contribution) and then add this back to the original scene colors. This can be done by drawing the scene to one texture, lighting to another, and copying/drawing one texture to another using multiply/additive blending etc.

[Mark SiblyKeymaster]

Actually, I think I might be able to do this just by writing a new ‘light’ shader…will have a play!

[therevillsParticipant]

Cool, thanks Mark

[therevillsParticipant]

I just had a hack around with the simplelight banana, and it is possible for 2d lights to work without normal maps.

Hoever, to make this work, I used a ‘default’ normal of 0,0,1. This is a massive cheat that may or may not look like crap depending on usage.

How did you do this in code?

[therevillsParticipant]

Bump?

[Mark SiblyKeymaster]

I wont be able to do this right away, I have some other stuff to finished up first.

[Mark SiblyKeymaster]

Sorry, but I’m a bit busy with other stuff and wont be able to look into this for a while yet.

You are of course welcome to try yourself! It should be fairly easy with a combination of multiply/additive blending and offscreen rendering. You are likely to have to tweaks things a bit anyway if you want to get *exactly* the same result as above which highly stylized.

[therevillsParticipant]

No worries – Just wondering how you did your hack on post #3?

[Mark SiblyKeymaster]

I did briefly hack LoadBump so it didn’t need an actual normal map to load – instead it used a default  0,0,1 normal map. This alone allowed you to run stuff like simplelight and lightsparks without having to use bump/specular maps. I reverted this though as I wanted to spend more time on it.

The only bit ‘wrong’ about this is the light intensity was still being multiplied by the ‘N dot L’ term of the lighting equation, which will give different intensities depending on relative positions of pixels/light, which is probably not want you want. I’m guessing you’re after a more full on 2d effect that ignores light direction etc, and this should be doable by tweaking the existing lighting shader a bit.

I now tend to think that just keeping everything 2d and hacking around with blending and offscreen rendering is probably the better solution anyway as even with a hacked lighting shader, you’re still gonna have to do some kludgy rendering to achieve the groovy ‘light cone’ effect. On the other hand, the light shader approach will actually integrate with shadows should  you want to use them.

Anyway, either approach will take a bit of time to experiment with, but like I say it could probably be done right now without having to get down with shaders by using a combo of fancy blending modes and offscreen rendering.

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