Modified the Phong shader, shadows no longer working properly - three.js

Question

So I spent quite a bit of time writing my own simple Phong shader before figuring that there must be some way to modify the existing three.js Phong shaders to suit my needs. What I ended up doing looked like this
var phongShader = THREE.ShaderLib.phong;
var phongMatUniforms = THREE.UniformsUtils.clone(phongShader.uniforms);
var uniforms = phongMatUniforms;
uniforms.currentTime = {
type : "f",
value : 1.0
};
uniforms.hourlyValues = {
type : "fv1",
value : hourlyValuesArray
}
Now that I had access to the Phong vertex and fragment shader, I went poking through the shader and modified the section that I thought would achieve what I was looking for :
//original Three.js phong shader line
mvPosition = modelViewMatrix * vec4( position, 1.0 );
//my edited / updated line
mvPosition = modelViewMatrix * vec4( position.x, position.y, position.z + interpolatedValue, 1.0 );
Great! Everything worked just like I thought it should. Then I decided to try and add shadows with a spotlight. The good news was that shadows worked but they didn't work with the geometry that the shader had modified. Here's a screenshot example:
http://imgur.com/8Sdxq60
So I figured that there must be somewhere else in the Phong vertex shader that needs another simple update. The problem is, I can't find it. It looked to me like this:
#if ! defined( USE_MORPHTARGETS ) && ! defined( USE_SKINNING )
//original shader code
vec4 worldPosition = modelMatrix * vec4( position, 1.0 );
//updated to account for distorted geometry
worldPosition = modelMatrix * vec4( position.x, position.y, position.z + interpolatedValue, 1.0 );
#endif
Should do the trick but all it did was produce the screenshot above.
I'm kind of at a loss here as to what / where in the shader I should be modifying to take into account my distorted geometry. It looks like this bit at the end:
#ifdef USE_SHADOWMAP
for( int i = 0; i < MAX_SHADOWS; i ++ ) {
vShadowCoord[ i ] = shadowMatrix[ i ] * worldPosition;
}
#endif
Sets the shadow varyings that I need, but updating "worldPosition" like I did should fix that, no?

Answer 1

Ok, so I found the relavant shaders for the shadow casting. They do reside in THREE.ShadowMapPlugin. Specifically there is a line :
if ( object.customDepthMaterial ) {
material = object.customDepthMaterial;
}
So you assign a material to the objects.customDepthMaterial.
I used:
var depthShader = THREE.ShaderLib[ "depthRGBA" ];
var depthUniforms = THREE.UniformsUtils.clone( depthShader.uniforms );
depthUniforms.currentTime = {
type : "f",
value : 1.0
};
depthUniforms.hourlyValues = {
type : "fv1",
value : hourlyValuesArray
}
As the basis for the depthmaterial and then assigned it to the object thusly:
extrudedMesh.customDepthMaterial = depthMaterial;
Worked like a charm. You can then update the uniforms for the depth material just like you would for any other material.