others blend modes ?

Community Forums/General Help/others blend modes ?

RemiD

(Posted 2016) [#1]

hello,

with Blitz3d, there are 3 blendmodes :
alpha
multiply
add

the uses and the formulas are :

Texture blending takes the highest order texture (the one with the highest index) and it blends with the texture below it, then that result to the texture directly below again, and so on until texture 0 which is blended with the polygons of the entity it is applied to and thus the world, depending on the EntityBlend of the object.

Entity blending determines the way in which the new RGBA of the pixel being rendered is combined with the RGB of the background.

To calculate the new RGBA of the pixel being rendered, the texture RGBA for the pixel (see TextureBlend for more information on how the texture RGBA is calculated) is taken, its alpha component multiplied by the entities/brushes (where applicable) alpha value and its color multiplied by the entities/brushes colour. This is the RGBA which will then be blended into the background pixel, and how this is done depends on the EntityBlend value.

Alpha
This blends the pixels according to the Alpha value. This is roughly done to the formula:

Rr = ( An * Rn ) + ( ( 1.0 - An ) * Ro )
Gr = ( An * Gn ) + ( ( 1.0 - An ) * Go )
Br = ( An * Bn ) + ( ( 1.0 - An ) * Bo )

Where R = Red, G = Green, B = Blue, n = new pixel colour values, r = resultant colour values, o = old pixel colour values.

Alpha blending is the default blending mode and is used with most world objects.

Multiply
This blend mode will darken the underlying pixels. If you think of each RGB value as being on a scale from 0% to 100%, where 0 = 0% and 255 = 100%, the multiply blend mode will multiply the red, green and blue values individually together in order to get the new RGB value, roughly according to:

Rr = ( ( Rn / 255.0 ) * ( Ro / 255.0 ) ) * 255.0
Gr = ( ( Gn / 255.0 ) * ( Go / 255.0 ) ) * 255.0
Br = ( ( Bn / 255.0 ) * ( Bo / 255.0 ) ) * 255.0

The alpha value has no effect with multiplicative blending. Blending a RGB value of 255, 255, 255 will make no difference, while an RGB value of 128, 128, 128 will darken the pixels by a factor of 2 and an RGB value of 0, 0, 0 will completely blacken out the resultant pixels. An RGB value of 0, 255, 255 will remove the red component of the underlying pixel while leaving the other color values
untouched.

Multiply blending is most often used for lightmaps, shadows or anything else that needs to 'darken' the resultant pixels.

Add
Additive blending will add the new color values to the old, roughly according to:

Rr = ( Rn * An ) + Ro
Gr = ( Gn * An ) + Go
Br = ( Bn * An ) + Bo

The resultant RGB values are clipped out at 255, meaning that multiple additive effects can quickly cause visible banding from smooth gradients.

Additive blending is extremely useful for effects such as laser shots and fire.

if you know others blend modes (in others tools or in others graphics engines), their uses and their formulas, can you please post them here ?

thanks,

Rick Nasher

(Posted 2016) [#2]

FastExt appear to has quite a few I believe, as seen in the FastExt.bb include file if it's of any use to you:

; -------------------- DirectX7 constants (only for TextureBlendCustom function) -----------------------
; Control
Const D3DTOP_DISABLE = 1 ; disables stage
Const D3DTOP_SELECTARG1 = 2 ; the Default
Const D3DTOP_SELECTARG2 = 3

; Modulate
Const D3DTOP_MODULATE = 4 ; multiply args together
Const D3DTOP_MODULATE2X = 5 ; multiply And 1 bit
Const D3DTOP_MODULATE4X = 6 ; multiply And 2 bits

; Add
Const D3DTOP_ADD = 7 ; add arguments together
Const D3DTOP_ADDSIGNED = 8 ; add With -0.5 bias
Const D3DTOP_ADDSIGNED2X = 9 ; As above but left 1 bit
Const D3DTOP_SUBTRACT = 10 ; Arg1 - Arg2, With no saturation
Const D3DTOP_ADDSMOOTH = 11 ; add 2 args, subtract product Arg1 + Arg2 - Arg1*Arg2 = Arg1 + (1-Arg1)*Arg2

; Linear alpha blend: Arg1*(Alpha) + Arg2*(1-Alpha)
Const D3DTOP_BLENDDIFFUSEALPHA = 12 ; iterated alpha
Const D3DTOP_BLENDTEXTUREALPHA = 13 ; texture alpha
Const D3DTOP_BLENDFACTORALPHA = 14 ; alpha from D3DRENDERSTATE_TEXTUREFACTOR Linear alpha blend With pre-multiplied arg1 input: Arg1 + Arg2*(1-Alpha)
Const D3DTOP_BLENDTEXTUREALPHAPM = 15 ; texture alpha
Const D3DTOP_BLENDCURRENTALPHA = 16 ; by alpha of current color

; Specular mapping
Const D3DTOP_PREMODULATE = 17 ; modulate With Next texture before use
Const D3DTOP_MODULATEALPHA_ADDCOLOR = 18 ; Arg1.RGB + Arg1.A*Arg2.RGB COLOROP only
Const D3DTOP_MODULATECOLOR_ADDALPHA = 19 ; Arg1.RGB*Arg2.RGB + Arg1.A COLOROP only
Const D3DTOP_MODULATEINVALPHA_ADDCOLOR = 20 ; (1-Arg1.A)*Arg2.RGB + Arg1.RGB COLOROP only
Const D3DTOP_MODULATEINVCOLOR_ADDALPHA = 21 ; (1-Arg1.RGB)*Arg2.RGB + Arg1.A COLOROP only

; Bump mapping
Const D3DTOP_BUMPENVMAP = 22 ; per pixel env map perturbation
Const D3DTOP_BUMPENVMAPLUMINANCE = 23 ; With luminance channel
; This can do either diffuse Or specular bump mapping With correct input.
; Performs the function (Arg1.R*Arg2.R + Arg1.G*Arg2.G + Arg1.B*Arg2.B)
; where each component has been scaled And offset To make it signed.
; The result is replicated into all four (including alpha) channels.
; This is a valid COLOROP only.
Const D3DTOP_DOTPRODUCT3 = 24

Const FETOP_PROJECT = $010000 ; FastExt constant for 2D projective texturing TextureCoords=0 (UV0)
Const FETOP_PROJECT0 = $010000 ; FastExt constant for 2D projective texturing TextureCoords=0 (UV0)
Const FETOP_PROJECT1 = $020000 ; FastExt constant for 2D projective texturing TextureCoords=1 (UV1)

Const FETOP_PROJECT3D = $050000 ; FastExt constant for 3D projective texturing TextureCoords=0 (UV0)
Const FETOP_PROJECT3D0 = $050000 ; FastExt constant for 3D projective texturing TextureCoords=0 (UV0)
Const FETOP_PROJECT3D1 = $060000 ; FastExt constant for 3D projective texturing TextureCoords=1 (UV1)

; -------------------- DirectX7 constants (only for EntityBlendCustom & BrushBlendCustom functions) -----------------------
Const D3DBLEND_ZERO = 1
Const D3DBLEND_ONE = 2
Const D3DBLEND_SRCCOLOR = 3
Const D3DBLEND_INVSRCCOLOR = 4
Const D3DBLEND_SRCALPHA = 5
Const D3DBLEND_INVSRCALPHA = 6
Const D3DBLEND_DESTALPHA = 7
Const D3DBLEND_INVDESTALPHA = 8
Const D3DBLEND_DESTCOLOR = 9
Const D3DBLEND_INVDESTCOLOR = 10
Const D3DBLEND_SRCALPHASAT = 11
Const D3DBLEND_BOTHSRCALPHA = 12
Const D3DBLEND_BOTHINVSRCALPHA = 13