# DX11 DX11 Multiple Shader Passing

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Migi0027    4628

Hi guys,

right now I'm having a program which is supposed to render multiple passes. So my theory was as following:

Shader Pass Color Alpha = 1.0f/AmountOfPasses

And this would be true for all shaders. But the problem is that it doesn't really work. It it like e.g. two passes, first.alpha: 0.5 second.alpha:1 or something like that?

Well my method doesn't really seem to work as the second pass isn't visible for some reason. But no matter if my shaders are somehow wrong, what is the correct way to render multiple passes to get one image?

cbuffer ConstantObjectBuffer
{
float4x4 final;
float4x4 rotation;
float4 ambientcol;
float3 space;
float alpha;
}

cbuffer ConstantFrameBuffer
{
float4 lightvec;
float4 lightcol;
}

struct VOut
{
float4 position : SV_POSITION;
float4 normal : NORMAL;
float4 color : COLOR;
};

VOut VShader(float4 position : POSITION, float4 normal : NORMAL)
{
VOut output;

output.position = mul(final, position);

// set the ambient light
output.color = ambientcol;

// calculate the diffuse light and add it to the ambient light
float4 norm = normalize(mul(rotation, normal));
float diffusebrightness = saturate(dot(norm, lightvec));
output.color += lightcol * diffusebrightness;

output.color.a = alpha;

return output;
}

{
return input.color;
}

The alpha amount is calculated in c++, like this:

ObjectBuffer.Alpha = 1.0f/(float)(Passes.getAlpha()); // .getAlpha = get all passes except lighting (e.g. texture, bump mapping...)
if (Passes.Lighting)
ObjectBuffer.Alpha += Lights.Directional.size();

Thank You

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Aqua Costa    3691
Just enable additive blending... No need to play with alpha values if all passes have the same alpha (adding to one).

P.S: I'm not sure if I understood you correctly, are you doing texture mapping, bump mapping, and lighting in different passes? Edited by TiagoCosta

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Migi0027    4628

I tried to enable additive blending, but nothing seemed to happen, here's how i did it:

D3D11_BLEND_DESC alphapassDesc = {0};
alphapassDesc.AlphaToCoverageEnable = true;
alphapassDesc.IndependentBlendEnable = true;

alphapassDesc.RenderTarget[0].BlendEnable = true;
alphapassDesc.RenderTarget[0].SrcBlend       = D3D11_BLEND_SRC_ALPHA;
alphapassDesc.RenderTarget[0].DestBlend      = D3D11_BLEND_INV_SRC_ALPHA;
alphapassDesc.RenderTarget[0].SrcBlendAlpha  = D3D11_BLEND_ONE;
alphapassDesc.RenderTarget[0].DestBlendAlpha = D3D11_BLEND_DEST_ALPHA;

dev->CreateBlendState(&alphapassDesc, &AlphaPassBS);


PS. I know somethings wrong

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Migi0027    4628

Is anything wrong with the code above?

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Migi0027    4628

If anyone is looking for a solution, this will do the trick

SrcBlend = D3D11_BLEND_ONE;
DestBlend = D3D11_BLEND_SRC1_COLOR;


Edited by Migi0027

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