;file field.vsh

; INPUT REGISTERS
;
; v0    Position
; v2    Normal
; v3	Vertex Colour

; CONSTANTS
;
; c10.w Effect strength
; c6 ... c9 World Matrix.
; c5  View vector
; c1 ... c4 Transform matrix
; c0  Screenspace transform offset

; TEMPS
;
; r1	ILU
; r2	Position
; r3	Accumulated Position
; r4	Normal
; r5	Accumulated Normal
; r6	Diffuse Clamp
; r11	Diffuse Colour

xvs.1.1
#pragma screenspace
    ; Transform -----------------------------------------------------------------------------------

    ; Transform position
    ; Combined camera & projection & screenspace scale matrix
    m4x4	oPos, v0, c1
    
    ;trick from the xds.graphics newsgroup - copy the output pos.w to fog
    ;mov     oFog.x, r12.w                                           ;dph is done by now

    ;compute 1/w
    rcc   r1.x, r12.w
           
    ;multiply 1/w through position & add screen space transform offset 
    mad     oPos.xyz, r12, r1.x, c0

    ;
    ; Compute glow on field.
    ; 
    ; Take the normalised distance from eye to vertex, and dot with
    ; the normal.

    ; Transform vertex to world space
    m4x3 r2, v0, c6
    
    ; c5 = camera pos
    sub r2.xyz, c5, r2			; r2 = view vector
    dp3 r3, r2, r2			
    rsq r3, r3
    mul r2.xyz, r2, r3			; r2 = normalize(r2)
    
    ;dp3 r3, v2, r2			; r3 = N dot V
    ;sub r2, v0.w, r3			; 1 - N dot V
    sub r2, v0.w, r2.y			; 1 - N dot V.  N = {0, 1, 0}
    mul oT0.xy, r2, r2			; squared
    
    mul oD0, v3, c10.w 			; vertex colour