particlesphere.psh

hl2 source code. Do not use it illegal.

ps.1.1

;------------------------------------------------------------------------------
; Sphere-lit particle pixel shader.
;
; The ParticleSphere lighting equation is:
; A + [[N dot |L - P|] * 0.5 + 0.5] * C * r / ||L - P||
;
; where:
; A = ambient light color
; N = particle normal (stored in the texture)
; L = light position
; P = point on surface
; C = directional light color
; r = directional light intensity
;
; This shader takes as input:
; t0	= Normal map texture coordinates (N)
; t1	= Light vector Normalize(L - P) * 0.5 in range [0,1]
; v0	= Directional color (C * r / ||L - P||^2) * 0.5
; v1	= Ambient light color (A)
; c0	= 0.5
;
; and outputs [v1 + (sample(t0) dot t1) * 0.5f + 0.5f]
;------------------------------------------------------------------------------

tex			t0						; Get the 3-vector from the normal map
texcoord	t1						; Interpret tcoord t1 as color data.

dp3			r1, t0_bx2, t1_bx2	; r0 = sample(t0) dot t1
add			r0, r1, c0			; + 0.5

mul			r1, v0, r0			; scale the dot product by the dirlight's actual color
add			r0.rgb, r1, v1			; add the ambient color in v1

mul			r0.a, t0, v0		; Alpha = normal map alpha * vertex alpha