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8up tuotlo

Help with Skinned Mesh shader

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I am use this HLSL D3DXEFFECT shader to draw my animated model in my application.

Shader model 3.0.




//-- Lighting ------
struct Direct
float3 pos;
float3 col;
Direct Dl[2];
float3 Al;
float3 eye;
float Sp;
float4x4 BM[60];
float4x4 Gm;
float4x4 Wm;
struct VS_in
float4 Pos  : POSITION;
float3 Norm : NORMAL;
float2 Tex  : TEXCOORD0;
float4 bi   : BLENDINDICES0;
float4 bw : BLENDWEIGHT0;
struct VS_out
float4 Pos  : POSITION;
float3 Norm : TEXCOORD1;
float2 Tex  : TEXCOORD0;
float3 wPos : TEXCOORD2;
float3 v    : TEXCOORD3;
VS_out vs(VS_in In)
VS_out Out;
float4x4 blend = BM[In.bi.x]*In.bw.x + BM[In.bi.y]*In.bw.y + BM[In.bi.z]*In.bw.z + BM[In.bi.w]*In.bw.w;
float4 SkinPos, SkinNorm;
SkinPos.x = (In.Pos.x * blend._11)+(In.Pos.z * blend._21)+(In.Pos.y * blend._31)+(blend._41);
SkinPos.z = (In.Pos.x * blend._12)+(In.Pos.z * blend._22)+(In.Pos.y * blend._32)+(blend._42);
SkinPos.y = (In.Pos.x * blend._13)+(In.Pos.z * blend._23)+(In.Pos.y * blend._33)+(blend._43);
SkinPos.w = 1.0f;
SkinNorm.x = (In.Norm.x * blend._11)+(In.Norm.z * blend._21)+(In.Norm.y * blend._31);
SkinNorm.z = (In.Norm.x * blend._12)+(In.Norm.z * blend._22)+(In.Norm.y * blend._32);
SkinNorm.y = (In.Norm.x * blend._13)+(In.Norm.z * blend._23)+(In.Norm.y * blend._33);
SkinNorm.w = 1.0f;
Out.Pos = mul(SkinPos, Gm);
Out.Tex = In.Tex;
Out.Norm = normalize(mul(SkinNorm, (float3x3)Wm));
Out.wPos = mul(SkinPos, Wm);
Out.v = eye.xyz - Out.wPos;
return Out;
float3 light(float3 n, float3 v)
float  nDotL[2];
nDotL[0] = saturate(dot(n, normalize(Dl[0].pos)));
nDotL[1] = saturate(dot(n, normalize(Dl[1].pos)));
float3 ret = Dl[0].col * nDotL[0] + Dl[1].col * nDotL[1] + Al;
/*+ (Dl[0].col * ((nDotL[0] == 0.0f) ? 0.0f : pow((saturate(dot(n, normalize(Dl[0].pos + v)))), Sp)));*/
return ret;
float4 ps(VS_out In) : COLOR0
return float4(light(normalize(In.Norm), normalize(In.v)), 1);
technique Standart
    pass P0
        VertexShader = compile vs_3_0 vs();
PixelShader  = compile ps_3_0 ps();



it is maximum of 60 bones by:


float4x4 BM[60];


when i try to set it to:


float4x4 BM[120];


shader not works.


Who knows why?

Can it be set to 120, and how if it is possible?

Edited by 8up tuotlo

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You're limited to 256 registers (float4) for constants. 60 * 4 = 240, which is okay. 120 * 4 > 256.


EDIT: For clarity - float4x4 is float4 times 4 = 4 registers. Also, beware, with 60 matrices taking up 240 registers, you're limited to just 16 additional constants.


float3 eye; // 1 register
float Sp; // 1 register
float4x4 BM[60]; // 240 registers
float4x4 Gm; // 4 registers
float4x4 Wm; // 4 registers


for 250 registers (of 256 available).

Edited by Buckeye

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Yup, up to 1024 bones if you do it naively. "Limitless" if you're doing it smart wink.png


But since you use SM3 you could use vertex texture fetch: Using a texture to hold your bone matrices and use several tex2Dlod in the vertex shader to load them.


There are other ways to address this limit: Split the mesh, use affine transformations (3x4 matrices), quaternions... Here's a recent discussion.



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