Mar
27
2012

Shadow Casting + Convex Hull = More Fake Shadows

An article by mgear

Combine Simple Shadow Casting & Monotone Chain Convex Hull and you have…more fake shadows for unity indie!!1

Works fine for a box..should try the teapot next.

Details:
– Calculate vectors from the light, through every vertex in target object, lengthen the vector until reach ground (y=0)
– You get list of points in the ground, convex hull them to get shadow outline
– Create shadow mesh from the convex hull points

Ideas:
– Try multiple lights? Multiple objects?
– Soft shadows? (shader)
– ShadowMesh could have trigger collider, to check if object enters shadow?
– Use ShadowMesh as a mask for something else..(?)
– Only cast shadows for objects in view? (or objects within _ – range from light?)
Webplayer:
http://unitycoder.com/upload/demos/ShadowCastingConvexHull2/

Download source:
shadowhull1.unityPackage

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Image#2: Deep profiler report (array sorting seems to take most of the time..)

Tags: casting, Convex Hull, fake, shadow, shadow caster, simple

About the Author:

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12 Comments + Add Comment

Marrt 28/03/2012 at 02:55

looks promising, always a pleasure to check your blog 😀

Reply
altare 29/03/2012 at 18:25

Interesting. Does this technique allow projection on uneven surfaces? That’d be very good to achieve.

Reply
- mgear 29/03/2012 at 21:49
  
  No it wouldnt work, as it just creates a flat (shadow) plane. Maybe with some modifications, but not sure how..
  
  Reply
j0no 11/04/2012 at 05:58

this is really kul!

Reply
JasonB 18/04/2012 at 21:31

This is what I need for a 2D project of mine. So basically, this, except simpler.

Do you think you could help me out with my forum thread when you have spare time? Casting mesh shadows is driving me up the wall, I just can’t figure it out. I’ve been trying for hours and I’m about two seconds away from total insanity.

http://forum.unity3d.com/threads/132728-Need-help-from-someone-who-understands-mesh-generation-%28Advanced%29.

Reply
- mgear 18/04/2012 at 22:22
  
  not sure if this would be the best for 2D..
  
  how about this kind of shader idea,
  http://forum.unity3d.com/threads/102079-Dynamic-shadows-in-Unity-Free-Pro-possibly-Mobile
  or those 2 links that i posted on the forum..
  
  Reply
Peter Matejovsky 30/07/2012 at 17:08

It is possible to obtain code for this? I would like to experiment or improve this. I just see code latter everywhere 🙂 Can you zip and email it please? I would be pleased.

Reply
- mgear 03/08/2012 at 02:30
  
  ..even a very small donation is enough for a special “Source-to-Your-Email”-service : )
  
  I’ll post it there later also..just would need to clean it up a bit, add comments etc.. but havent had the time yet..
  
  Reply
clams 14/12/2013 at 15:04

Hey there, really nice work, could you possibly share the code for this? I would be very grateful!! 🙂 (trying to build something similar for a university game prototype…)

Reply
- mgear 14/12/2013 at 15:36
  
  yes, i’ll add it within few days (remind me if i forgot : )
  
  Reply
  - clams 14/12/2013 at 15:46
    
    cool thx a lot! 🙂
    
    Reply
    - mgear 15/12/2013 at 18:24
      
      added source, but something is broken (tested on 4.3), shadow is not visible..(?)
      
      Reply