Loading and Rendering Milkshape 3D Models with Animation and Skinning

/*
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Author:
Boroş Tiberiu
Administrator Sistem                                                    Tel.: +40745310081
Institutul de Cercetări pentru Inteligenţă Artificială,
Academia Română
Calea 13 Septembrie, Nr. 13, CASA ACADEMIEI, Bucuresti 050711, ROMANIA
Tel.: +40-(0)213188103
Fax: +40-(0)213188142
E-mail: office@racai.ro
Web: http://www.racai.ro
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 */
attribute vec4 position;
attribute vec3 normal;
attribute vec4 weight;
attribute vec4 index;
attribute float numBones;

uniform mat4 matGlobal[100];
uniform mat4 matGlobalSkeleton[100];
uniform vec4 color;
uniform vec4 lightPos;

float DotProduct(in vec4 x, in vec4 y) {
    return x[0] * y[0] + x[1] * y[1] + x[2] * y[2];
}

void VectorRotate(in vec4 in1, in mat4 in2, out vec4 rez) {
    rez[0] = DotProduct(in1, in2[0]);
    rez[1] = DotProduct(in1, in2[1]);
    rez[2] = DotProduct(in1, in2[2]);
}

void VectorIRotate(in vec4 in1, in mat4 in2, out vec4 rez) {
    rez[0] = in1[0] * in2[0][0] + in1[1] * in2[1][0] + in1[2] * in2[2][0];
    rez[1] = in1[0] * in2[0][1] + in1[1] * in2[1][1] + in1[2] * in2[2][1];
    rez[2] = in1[0] * in2[0][2] + in1[1] * in2[1][2] + in1[2] * in2[2][2];
}

void VectorTransform(in vec4 in1,in mat4 in2, out vec4 rez) {
    rez[0] = DotProduct(in1, in2[0]) + in2[0][3];
    rez[1] = DotProduct(in1, in2[1]) + in2[1][3];
    rez[2] = DotProduct(in1, in2[2]) + in2[2][3];
}

void VectorITransform(in vec4 in1, in mat4 in2, out vec4 rez) {
    vec4 tmp;
    tmp[0] = in1[0] - in2[0][3];
    tmp[1] = in1[1] - in2[1][3];
    tmp[2] = in1[2] - in2[2][3];
    VectorIRotate(tmp, in2, rez);
}

void main()
{
    vec4 transformedPosition = vec4(0.0);
    vec3 transformedNormal = vec3(0.0);

    vec4 curIndex = index;
    vec4 curWeight = weight;

    for (int i = 0; i < int(numBones); i++)
    {
        mat4 g44 = matGlobal[int(curIndex.x)];
        mat4 s44 = matGlobalSkeleton[int(curIndex.x)];
        vec4 vert = vec4(0);
        vec4 norm = vec4(0);
        vec4 tmpNorm = vec4(0);
        vec4 tmpVert = vec4(0);

        VectorITransform(gl_Vertex, s44, tmpVert);
        VectorTransform(tmpVert, g44, vert);
        vert[3]=1;
        transformedPosition += vert * curWeight.x;

        vec4 preNormal=vec4(normal.xyz,1);
        VectorIRotate(preNormal, s44, tmpNorm);
        VectorRotate(tmpNorm, g44, norm);
        norm[3]=1;
        transformedNormal += vec3(norm.xyz) * curWeight.x;

        // shiftam sa avem urmatoarele valori pentru pondere si indice de os
        curIndex = curIndex.yzwx;
        curWeight = curWeight.yzwx;
    }

    gl_Position = gl_ModelViewProjectionMatrix * transformedPosition;

    transformedNormal = normalize(transformedNormal);
    gl_FrontColor = dot(transformedNormal, lightPos.xyz) * color;
}