special blend needed in xna 4.0

Question

i got 2 dynamic texture ,and want add second texture color to first texture color But just where first texture color alpha is not 0 something like inverse transparncey i add two pic link to show what is my mean:

TO

just collisions part must add two texture pixel color

ty for your help

This isn't so much "add" as "replace". If you add them, then you'd end up with magenta spots I think. Otherwise some sort of "add" that only effected the RGB channels and ignored A would do what you want. Sorry I can't be much more help than that :) — Merlyn Morgan-Graham, Oct 17 '11 at 06:48

score 1 · Answer 1 · answered Oct 16 '11 at 21:12

Maybe using BlendState.Additive wil be enough for you.

or maybe it can be achieved with a custom BlendState.. but I have not experience with this...

or you can make a shader, you should note that you have to quads:

Quad with a rag doll. (Qrd)
Quad with a circle. (Qc)

you draw Qc over Qrd...

so you have to traduce the texture coordinates that you get in the pixel shader that owns to Qc to texture cordinates at Qrd space...

then you sample the color from Qrd texture, and if alpha is near zero you clip the pixel... else you return the sample from Qrc texture

im kind noob with 2d shader ,can you show asample for this shader plz? — mX64, Oct 17 '11 at 05:40

score 1 · Accepted Answer · answered Oct 17 '11 at 07:39

1

just did it , works great

sampler circleSampler : register(s1);
sampler playerSampler : register(s0);

float4 main(float4 color : COLOR0 ,float2 texCoord : TEXCOORD0):COLOR0
{
float4 output = float4(1,1,1,1);
float4 CircColor = tex2D(circleSampler,texCoord);
float4 playerColor = tex2D(playerSampler,texCoord);
if (CircColor.a ==0)
{
output = playerColor;
}
else
{
output = CircColor* playerColor;
}
output.a = playerColor.a;
return output;
}

technique Technique1
{
    pass Pass1
    {

        PixelShader = compile ps_2_0 main();
    }
}

anyway ty for ur time

answered Oct 17 '11 at 07:39

mX64

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you have not transformed texture coordinates, so is right if your textures have same size and are drawed in the same position... – Blau Oct 17 '11 at 10:13
yea , both texture have same sizes , ty for your attention :D – mX64 Oct 17 '11 at 11:08

special blend needed in xna 4.0

2 Answers2