Overgrowth takes place in the savage world of Lugaru where rabbits, wolves and other animals are forced to use paws, claws and medieval weaponry to engage each other in battle. Combining 3rd person adventure platforming with intricate melee combat, Overgrowth achieves a unique feel. Overgrowth also benefits from Wolfire's brand new Phoenix Engine which has been built from the ground up to allow the use of cutting edge graphics, animation, and physics. Add to these exciting features Overgrowth’s realistic artificial intelligence and streamlined control system and the result is an astoundingly immersive experience.

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When I loaded Aubrey's new rabbit model, it was clear that we needed a new rendering method in order to do it justice. Our basic object shader works best for hard surfaces like wood, leather and stone, not fuzzy ones like fur and cloth.

Posted by jeffr on Oct 1st, 2009

When I loaded Aubrey's new rabbit model, it was clear that we needed a new rendering method in order to do it justice. Our basic object shader works best for hard surfaces like wood, leather and stone, not fuzzy ones like fur and cloth. This problem was most obvious when the model was lit from behind:


It suffers from the 'plaster effect' -- it doesn't have the subtle shading effects that characterize the materials, so the surfaces that should look soft instead look harsh and rigid. In real life, fur and cloth always have tiny stray fibers that catch the light when lit from behind, giving a 'halo' effect. We can start to approximate this halo by lighting up surfaces that are perpendicular to our viewing direction, like this:


This is often used as a 'selection' effect in 3D games because it's an easy way to highlight edges. However, it needed to be toned down before we could use it as a realistic effect. First, I decided to modulate the brightness of the highlight by a softer version of the standard lighting equation, so that surfaces facing directly away from the light remain in shadow.


Finally, I used one of our unused texture channels (the alpha channel of the normal map) to specify which parts of the model are affected by rim lighting. This gives us detailed control of how fuzzy each surface should look. Here's the final shader applied to the rabbit model:


While I don't have time to make a detailed fur shader yet, I thought this effect went a long way towards making the rabbit's fur and clothes read as 'soft' materials. Does this effect work for you? Can you think of any ways that I could improve it? (permalink)

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Larceny196 Oct 1 2009 says:

Looks good to me really. A bit of changing of textures and a bit better lighting would be better. But for the most part good job.

+1 vote     reply to comment
Elementalist Oct 1 2009 says:

I'm kinda curious... You say you used the unused texture channel, the alpha channel of the normal map, but to specify which areas are affected by the rim lighting.

This makes it sound like really, you can do whatever you want with a texture channel, what's the point of specifying it with a name (such as normal map alpha channel) when it doesn't have to specifically be that? Why aren't they just texture channels?

+1 vote     reply to comment
jeffr Author
jeffr Oct 1 2009 replied:

Well, in the file format they are four chanels: RGBA. They don't have to be used for that, but it's good to keep track. ;)

+1 vote   reply to comment
NGS616 Oct 1 2009 says:

That is great lighting! I seen that rabbit model over on poly count that thing is amazing.

+1 vote     reply to comment
Nebcake Oct 1 2009 says:

A very smart idea you used their, great job

+1 vote     reply to comment
Assaultman67 Oct 1 2009 says:

yea, i definitely need to work on making shaders ... mine never do the model justice

I was reading your article and looking at the pictures and was like "Yea ... ok ... ok ... where is he going with this? ... Holy crap thats good! O_O"

+1 vote     reply to comment
chris_sloany Oct 1 2009 says:

awesome job!!

+1 vote     reply to comment
awesomepossum Oct 1 2009 says:

It tis awful purdy! nice work

+1 vote     reply to comment
PringleX Oct 1 2009 buried:


Phong shading.

-6 votes     reply to comment
vfn4i83 Oct 2 2009 says:

Nice touch, the characters are going to look awesome that way.

+1 vote     reply to comment
Joe_Shmoe Oct 2 2009 says:

This is rather fascinating... This is why I love developer notes, so much to learn from others, and some developers cover even the smallest of things like this =] btw realy well done with this, easy to read and understand and probably a simple thing to miss (i know i did when i saw the first post of the model in the level, never paid that much attention to the lighting and apearance) but awsum info, thanx for sharing

+3 votes     reply to comment
hushpuppy Oct 2 2009 says:

The third model looks Call of duty 4'ish, they had no idea what subelty is.

Really nice work, the last one is diffinatly perfect ammount.

+1 vote     reply to comment
pvt.Johnson Oct 2 2009 replied:

Its the way the lighting hits the characters is in that game, i can see what you mean.

+1 vote     reply to comment
deathparadeNL Oct 2 2009 says:

looking really good nice work keep on going like this :)

+1 vote     reply to comment
kinesis916 Oct 2 2009 says:

That's awesome.

+1 vote     reply to comment
KEEP_IT_UP! Oct 2 2009 says:

love it! keep it up ;)

+1 vote     reply to comment
Myloman Oct 2 2009 says:

Looking wonderful. It's great that you logically explain things in an easy to understand manner, so that we may all learn from your development. Makes each update rewarding and exciting :).

+1 vote     reply to comment
DOLBYdigital Oct 2 2009 says:

Another great update that was both interesting and educational :)
Love all the time you guys are putting into not only perfecting this game but also showing your thought process and procedures. I have been saying this a lot but its really time for me to pre-order and jump into the alphas !

Keep up the great work team

+1 vote     reply to comment
Bird_of_Prey Oct 2 2009 says:

Really nice effect. Gives some nice depth to the character.

+1 vote     reply to comment
maniacmoop Oct 2 2009 says:

I enjoy rabbit incest.

-3 votes     reply to comment
jeffr Author
jeffr Oct 2 2009 replied:


+1 vote   reply to comment
masterofhobbiton Oct 2 2009 says:

The final picture is incredible!

+1 vote     reply to comment
Ka! Oct 2 2009 says:

now THAT's what a rimjob should be. ;o
I kid!

Looks great, as with all the updates. o.o

+1 vote     reply to comment
doublethink Oct 3 2009 says:

So many games mess this up, I'm talking major retail titles too.

Nice to see you take notice.

+1 vote     reply to comment
Atlasfield Oct 3 2009 says:

Pretty interesting, I was wondered how looks in front the face of the character.

+1 vote     reply to comment
vp21ct Oct 3 2009 says:


+1 vote     reply to comment
dill1233 Oct 7 2009 says:

Wow, looks great! I love the way how you guys have all of these little details that you get really in def with and explain your little tricks on those little details. I can't wait to see you mesh every one of those little details into one big product that will be so perfect in every which way. Keep it up!

+1 vote     reply to comment
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