#version 120

/**
 * Lit Sphere (spherically mapped captured light) shader.
 *
 **Project Name:**      MakeHuman
 *
 **Product Home Page:** http://www.makehumancommunity.org/
 *
 **Github Code Home Page:**    https://github.com/makehumancommunity/
 *
 **Authors:**           Jonas Hauquier
 *
 **Copyright(c):**      MakeHuman Team 2001-2020
 *
 **Licensing:**         AGPL3
 *
 *
 * Abstract
 * --------
 *
 * Has the effect of a specular material, shaded relative to the camera without
 * lights.
 * The normal is used as UV coordinates of the litsphere texture, which is a
 * spherically shaped mapping of colors for all angles that normals can face in
 * the half sphere facing the camera.
 * Litsphere textures express lighting for normal angles in view space.
**/

#ifdef DIFFUSE
    uniform sampler2D diffuseTexture;
#else
    #ifdef ALPHA_MAP
        uniform sampler2D alphaTexture;
    #endif
#endif

#ifdef AOMAP
    uniform sampler2D aomapTexture;
#endif


#ifdef NORMALMAP
    uniform sampler2D normalmapTexture;
    uniform float normalmapIntensity = 1.0;
    //define CALC_NORMAL_Z

    // Inputs
    varying mat3 tbnMat;    // Conversion matrix from tangent to view space
#else
    // Inputs
    varying vec3 vNormal;   // Vertex normal in view space
#endif

// Lit Sphere texture
uniform sampler2D litsphereTexture;

// Additive litsphere shading. Useful for specularity litspheres
// Specifies the amount of litsphere shading that will be added instead of multiplied.
uniform float AdditiveShading = 0.0;


void main() {

    #ifdef NORMALMAP
        #ifdef CALC_NORMAL_Z
            vec2 normalH = 0.5 * texture2D(normalmapTexture, gl_TexCoord[0].xy).rg;
            vec3 normal;
            normal.xy = (2.0 * normalH -1.0) * normalmapIntensity;
            normal.z = sqrt(1.0 - dot(normal.xy, normal.xy));
        #else
            vec3 normalH = texture2D(normalmapTexture, gl_TexCoord[0].xy).rgb;
            vec3 normal = (2.0 * normalH -1.0) * normalmapIntensity;
        #endif

        // Convert sampled normal from tangent to view space
        normal = normalize(tbnMat * normal);
    #else
        vec3 normal = vNormal;
    #endif

    vec3 shading = texture2D(litsphereTexture, vec2(normal.xyz * vec3(0.495) + vec3(0.5))).rgb;

    #ifdef VERTEX_COLOR
        shading = shading * gl_Color.rgb;
    #endif

    vec4 outColor;
    #ifdef DIFFUSE
        vec4 diffuse = texture2D(diffuseTexture, gl_TexCoord[0].xy).rgba;
        outColor.rgb = (1.0 - AdditiveShading)*shading * diffuse.rgb * vec3(2.0 - (shading.r + shading.g + shading.b)/3.0);
        outColor.rgb += AdditiveShading*(shading + diffuse.rgb);
        outColor.a = diffuse.a;
    #else
        outColor.rgb = shading.rgb;
        #ifdef ALPHA_MAP
            outColor.a = texture2D(alphaTexture, gl_TexCoord[0].xy).a;
        #else
            outColor.a = 1.0;
        #endif
    #endif

    #ifdef AOMAP
        outColor.rgb = outColor.rgb * texture2D(aomapTexture, gl_TexCoord[0].xy).rgb;
    #endif

    gl_FragColor.rgba = outColor.rgba;

}

