rendering - some questions about cg shader program (Depth Shadow Mapping in OGRE) -

i doing depth shadow mapping,and learning tutorial (http://www.ogre3d.org/tikiwiki/depth+shadow+mapping)

i have 3 questions following:

(1)is right when use custom shadow caster,i can depth in shadow receiver using "uniform sampler2d shadowmap "?

void castervp( out float2 outdepth        : texcoord0) {     outpos = mul(worldviewproj, position);     outdepth.x = (outpos.z - depthrange.x) * depthrange.w; } void casterfp( float2 depth            : texcoord0,               out float4 result        : color) {     result = float4(finaldepth, finaldepth, finaldepth, 1); }  //shadow receiver fragment program void receiverfp(uniform sampler2d   shadowmap       : register( s0 )) { } 

(2) not sure matrix(texture_viewproj_matrix) used for.

i guess,

texture coordinate->camera coordinate->screen coordinate??

and texture coordinates should 2-d. right?

(3) in shadow receiver fragment shader,i don't know line mean. and,do these 3 variable(finalcenterdepth,shadowuv.z , vertexcolour) stand depth?

result = (finalcenterdepth > shadowuv.z) ? vertexcolour : float4(0,0,0,1); 

thank you~ advice useful newbie :d

(1) not sure if understood question correctly. if wrote depth render target can read associated texture.

(2) texture_viewproj_matrix transforms world space light's screen space , rescales resulting xy [-1;1] [0;1]. in xy/w shadow map uv coordinates of receiver , in z - shadow map depth of receiver.

(3) finalcenterdepth - depth read shadow map , adjusted depth bias in order fix acne artifacts. shadowuv.z - depth of receiver adjusted depth bias. vertexcolour - lit color, calculated in vertex shader (see outcolour in receivervp).