How to project shadows using a vertex shader

This is the basic logic, you upload 2 sets of 2 points, start and end. Along with each set you upload a different “Bool” value that is represented with 1 or 0. Multiply the projected normal but the Bool. 1 will project a ray, 0 will remain at original shadow caster vertex.

here is some code I found from this link: http://ryanspeets.com/flash/how-i-did-my-2d-shadow-rendering-with-stage3d-tutorial/

alias vc0.xy, CONST_0( 0, 1 )
alias vc0.z, shadowDistance
alias va0, vertexPosition
alias vc1, lightPosition

vt0.xy = vertexPosition.xy - lightPosition.xy
vt0.xy *= vertexPosition.z
vt0.xy *= shadowDistance
vt1.xy = vertexPosition.xy + vt0.xy
vt1.z = 0
vt1.w = 1
op = mul4x4(vt1, vc2)

this is AGALMacro, so treat it like pseudocode if you are using MiniAssembler or HXSL.

Hope you guys can make something out of it, enjoy!

thats effing cool qwerber!
I DLed the source so I could play the app. Its really sweet and really easy to imagine it fitting into a zombie||nuclear apoc||haunted house game.

I think I’m going to try to combine it with this collision detection I made so that the light is emanating from a flash light beam, and it knows when/when it can’t go around corners and such.