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.fx shader with skinning branch disappears in Softimage viewport

Last post 02/10/2009 17:07 by raabix. 0 replies.
  • 02/10/2009 17:07

    .fx shader with skinning branch disappears in Softimage viewport

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    I have an awkward problem that I came across and it seems totally unexplainable to me:

    I am trying to implement a shader using skinning as presented on the Digital Tutors DVD (and following therefore the same approach as the shaders that come with the MOD Tool).
    There is a boolean variable that allows me to turn skinning on and off, so the vertex shader has two branches. The weird fact is, that the skinning calculation messes up the shader in a way, that its not rendered anymore to the viewport, no matter what value the boolean UseBones has. Commenting out the four lines that do the skinning transformation 'fixes' the problem in a way that the not-skinned branch creates the right result and renders to the viewport properly. (While the skinned version disappears as expected because we're not seeing any skinning information yet)

    Here's the code: The problematic lines are at line 120.

    1 // 
    2 // The state structure is used internally within the fragment shader to 
    3 // commonly used values. 
    4 // 
    5 struct State 
    6 { 
    7     float4 tex_coord[4]; 
    8     float3 tangent[1]; 
    9     float3 binormal[1]; 
    10     float3 position; 
    11     float3 origin; 
    12     float3 normal; 
    13     float3 direction; 
    14     float ray_length; 
    15 }; 
    16
    17
    18 #define MaxBones 58 
    19 float4x4 Bones[MaxBones]; 
    20 bool UseBones 
    21 < 
    22     string SasUiLabel = "Use Bones"; 
    23     string SasUiControl = "Any"; 
    24 > = false; 
    25  
    26 // 
    27 // The following are parameters representing non-varying state variables  
    28 // referenced by the shader. These should be set by the application at runtime. 
    29 // Note that vector parameters should be provided in camera space. 
    30 // 
    31 float4x4 __object_to_ndc : WorldViewProjection 
    32 < 
    33     string UIWidget = "none"; 
    34 >; 
    35 float4x4 __world_to_object : WorldInverse 
    36 < 
    37     string UIWidget = "none"; 
    38 >; 
    39 float4x4 __object_to_world : World 
    40 < 
    41     string UIWidget = "none"; 
    42 >; 
    43 float4x4 __view : View 
    44 < 
    45     string SasUiControl = "none"; 
    46 >; 
    47 float4x4 __camera_to_world : ViewInverse 
    48 < 
    49     string UIWidget = "none"; 
    50 >; 
    51 float4x4 __projection : Projection 
    52 < 
    53     string SasUiControl = "none"; 
    54 >; 
    55  
    56 // 
    57 // The App2vert structure defines the vertex attributes used by the vertex 
    58 // shader. The application should supply a vertex stream containing these  
    59 // elements. 
    60 // 
    61 struct App2vert 
    62 { 
    63     float3 position : POSITION; 
    64     float3 normal : NORMAL; 
    65         // for skinning (not used by XSI however) 
    66     float4 BoneIndices : BLENDINDICES0; 
    67     float4 BoneWeights : BLENDWEIGHT0; 
    68 }; 
    69  
    70 // 
    71 // The Vert2frag_out structure defines values output by the vertex shader. 
    72 // 
    73 struct Vert2frag_out 
    74 { 
    75     float4 hpos : POSITION; 
    76     float3 position : TEXCOORD6; 
    77     float3 normal : TEXCOORD7; 
    78 }; 
    79  
    80 // 
    81 // The Vert2frag_in structure defines values used by the fragment shader. 
    82 // 
    83 struct Vert2frag_in 
    84 { 
    85     float4 hpos : POSITION; 
    86     float3 position : TEXCOORD6; 
    87     float3 normal : TEXCOORD7; 
    88 }; 
    89  
    90 // 
    91 // This function is the main method of the vertex shader. 
    92 // 
    93 Vert2frag_out vertex_main( 
    94     App2vert vs_in) 
    95 { 
    96     Vert2frag_out vs_out; 
    97     float4 position = float4(vs_in.position, 1); 
    98     vs_out.hpos = mul(position, __object_to_ndc); 
    99     vs_out.position = mul(position, __object_to_world).xyz; 
    100     vs_out.normal = mul((float3x3)__world_to_object, vs_in.normal); 
    101     return vs_out; 
    102 } 
    103  
    104 // 
    105 // This function is the main method of the skinned vertex shader. 
    106 // 
    107 Vert2frag_out skinned_vertex_main( 
    108     App2vert vs_in) 
    109 { 
    110     Vert2frag_out vs_out; 
    111      
    112     float4 position = float4(vs_in.position, 1); 
    113     float4 HPOS = float4(0, 0, 0, 0); 
    114     if( UseBones == true) 
    115     { 
    116         float4x4 skinTransform = 0; 
    117     // When the next 4 lines are commented out, the shader displays fine in Softimage. 
    118     // But putting enabling one or more will make the shader disappear completely in the 
    119     // Softimage viewport, no matter what value "UseBones" is set to 
    120         skinTransform += Bones[vs_in.BoneIndices.x] * vs_in.BoneWeights.x; 
    121         skinTransform += Bones[vs_in.BoneIndices.y] * vs_in.BoneWeights.y; 
    122         skinTransform += Bones[vs_in.BoneIndices.z] * vs_in.BoneWeights.z; 
    123         skinTransform += Bones[vs_in.BoneIndices.w] * vs_in.BoneWeights.w; 
    124          
    125         // Skin the vertex position 
    126         float4 weightedPosition = mul(position, skinTransform); 
    127         HPOS = mul(mul(weightedPosition, __view), __projection); 
    128         vs_out.normal = normalize(mul(float3(vs_in.normal.xyz), 
    129                      (float3x3)skinTransform)); 
    130         vs_out.position = weightedPosition; 
    131     } 
    132     else 
    133     { 
    134         HPOS = mul(position, __object_to_ndc); // TMP 
    135         vs_out.position = mul(position, __object_to_world).xyz; 
    136         vs_out.normal = mul((float3x3)__world_to_object, vs_in.normal); 
    137     } 
    138     vs_out.hpos = HPOS; 
    139     return vs_out; 
    140 } 
    141  
    142 // 
    143 // This function is the main method of the fragment shader. It initializes the 
    144 // values in the state structure that are used by nodes in the shader graph 
    145 // and produces the final result of the shader. 
    146 // 
    147 float4 fragment_main( 
    148     Vert2frag_in fs_in) : COLOR 
    149 { 
    150     State state; 
    151     state.position = fs_in.position; 
    152     state.normal = normalize(fs_in.normal); 
    153     state.origin = __camera_to_world[3]; 
    154     float3 eye_to_pos = state.position - state.origin; 
    155     state.ray_length = length(eye_to_pos); 
    156     state.direction = eye_to_pos/state.ray_length; 
    157     return float4(0.4, 0.2, 0.8, 1.0); 
    158 } 
    159  
    160  
    161 // 
    162 // The following define the default technique and pass of the effect. 
    163 // 
    164 technique T0 
    165 { 
    166     pass P0 
    167     { 
    168         ZEnable      = true; 
    169         ZWriteEnable = true; 
    170         CullMode     = none; 
    171         VertexShader = compile vs_3_0 skinned_vertex_main(); 
    172         PixelShader  = compile ps_3_0 fragment_main(); 
    173     } 
    174 } 
    175  
    176  

    The shader works fine in FX Composer 2.5, so I suspect the error to lie somewhere in Mod Tool 7.5 (which I'm using). I could possibly get around this problem by separating the shader into a skinned and an unskinned Technique, however I'd like to follow the approach that is suggested in the tutorials.

    Cheers,
    Ruediger
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