g3n-engine/renderer/shaders/sources.go

// File generated by G3NSHADERS. Do not edit.
// To regenerate this file install 'g3nshaders' and execute:
// 'go generate' in this folder.

package shaders

const include_attributes_source = `//
// Vertex attributes
//
layout(location = 0) in  vec3  VertexPosition;
layout(location = 1) in  vec3  VertexNormal;
layout(location = 2) in  vec3  VertexColor;
layout(location = 3) in  vec2  VertexTexcoord;
layout(location = 4) in  float VertexDistance;
layout(location = 5) in  vec4  VertexTexoffsets;


`

const include_lights_source = `//
// Lights uniforms
//

// Ambient lights uniforms
#if AMB_LIGHTS>0
    uniform vec3 AmbientLightColor[AMB_LIGHTS];
#endif

// Directional lights uniform array. Each directional light uses 2 elements
#if DIR_LIGHTS>0
    uniform vec3 DirLight[2*DIR_LIGHTS];
    // Macros to access elements inside the DirectionalLight uniform array
    #define DirLightColor(a)		DirLight[2*a]
    #define DirLightPosition(a)		DirLight[2*a+1]
#endif

// Point lights uniform array. Each point light uses 3 elements
#if POINT_LIGHTS>0
    uniform vec3 PointLight[3*POINT_LIGHTS];
    // Macros to access elements inside the PointLight uniform array
    #define PointLightColor(a)			PointLight[3*a]
    #define PointLightPosition(a)		PointLight[3*a+1]
    #define PointLightLinearDecay(a)	PointLight[3*a+2].x
    #define PointLightQuadraticDecay(a)	PointLight[3*a+2].y
#endif

#if SPOT_LIGHTS>0
    // Spot lights uniforms. Each spot light uses 5 elements
    uniform vec3  SpotLight[5*SPOT_LIGHTS];
    
    // Macros to access elements inside the PointLight uniform array
    #define SpotLightColor(a)			SpotLight[5*a]
    #define SpotLightPosition(a)		SpotLight[5*a+1]
    #define SpotLightDirection(a)		SpotLight[5*a+2]
    #define SpotLightAngularDecay(a)	SpotLight[5*a+3].x
    #define SpotLightCutoffAngle(a)		SpotLight[5*a+3].y
    #define SpotLightLinearDecay(a)		SpotLight[5*a+3].z
    #define SpotLightQuadraticDecay(a)	SpotLight[5*a+4].x
#endif

`

const include_material_source = `//
// Material properties uniform
//

// Material parameters uniform array
uniform vec3 Material[6];
// Macros to access elements inside the Material array
#define MatAmbientColor		Material[0]
#define MatDiffuseColor     Material[1]
#define MatSpecularColor    Material[2]
#define MatEmissiveColor    Material[3]
#define MatShininess        Material[4].x
#define MatOpacity          Material[4].y
#define MatPointSize        Material[4].z
#define MatPointRotationZ   Material[5].x

#if MAT_TEXTURES > 0
    // Texture unit sampler array
    uniform sampler2D MatTexture[MAT_TEXTURES];
    // Texture parameters (3*vec2 per texture)
    uniform vec2 MatTexinfo[3*MAT_TEXTURES];
    // Macros to access elements inside the MatTexinfo array
    #define MatTexOffset(a)		MatTexinfo[(3*a)]
    #define MatTexRepeat(a)		MatTexinfo[(3*a)+1]
    #define MatTexFlipY(a)		bool(MatTexinfo[(3*a)+2].x)
    #define MatTexVisible(a)	bool(MatTexinfo[(3*a)+2].y)
#endif

// GLSL 3.30 does not allow indexing texture sampler with non constant values.
// This macro is used to mix the texture with the specified index with the material color.
// It should be called for each texture index. It uses two externally defined variables:
// vec4 texColor
// vec4 texMixed
#define MIX_TEXTURE(i)                                                                       \
    if (MatTexVisible(i)) {                                                                  \
        texColor = texture(MatTexture[i], FragTexcoord * MatTexRepeat(i) + MatTexOffset(i)); \
        if (i == 0) {                                                                        \
            texMixed = texColor;                                                             \
        } else {                                                                             \
            texMixed = mix(texMixed, texColor, texColor.a);                                  \
        }                                                                                    \
    }

`

const include_phong_model_source = `/***
 phong lighting model
 Parameters:
    position:   input vertex position in camera coordinates
    normal:     input vertex normal in camera coordinates
    camDir:     input camera directions
    matAmbient: input material ambient color
    matDiffuse: input material diffuse color
    ambdiff:    output ambient+diffuse color
    spec:       output specular color
 Uniforms:
    AmbientLightColor[]
    DiffuseLightColor[]
    DiffuseLightPosition[]
    PointLightColor[]
    PointLightPosition[]
    PointLightLinearDecay[]
    PointLightQuadraticDecay[]
    MatSpecularColor
    MatShininess
*****/
void phongModel(vec4 position, vec3 normal, vec3 camDir, vec3 matAmbient, vec3 matDiffuse, out vec3 ambdiff, out vec3 spec) {

    vec3 ambientTotal  = vec3(0.0);
    vec3 diffuseTotal  = vec3(0.0);
    vec3 specularTotal = vec3(0.0);

#if AMB_LIGHTS>0
    // Ambient lights
    for (int i = 0; i < AMB_LIGHTS; i++) {
        ambientTotal += AmbientLightColor[i] * matAmbient;
    }
#endif

#if DIR_LIGHTS>0
    // Directional lights
    for (int i = 0; i < DIR_LIGHTS; i++) {
        // Diffuse reflection
        // DirLightPosition is the direction of the current light
        vec3 lightDirection = normalize(DirLightPosition(i));
        // Calculates the dot product between the light direction and this vertex normal.
        float dotNormal = max(dot(lightDirection, normal), 0.0);
        diffuseTotal += DirLightColor(i) * matDiffuse * dotNormal;
        // Specular reflection
        // Calculates the light reflection vector
        vec3 ref = reflect(-lightDirection, normal);
        if (dotNormal > 0.0) {
            specularTotal += DirLightColor(i) * MatSpecularColor * pow(max(dot(ref, camDir), 0.0), MatShininess);
        }
    }
#endif

#if POINT_LIGHTS>0
    // Point lights
    for (int i = 0; i < POINT_LIGHTS; i++) {
        // Common calculations
        // Calculates the direction and distance from the current vertex to this point light.
        vec3 lightDirection = PointLightPosition(i) - vec3(position);
        float lightDistance = length(lightDirection);
        // Normalizes the lightDirection
        lightDirection = lightDirection / lightDistance;
        // Calculates the attenuation due to the distance of the light
        float attenuation = 1.0 / (1.0 + PointLightLinearDecay(i) * lightDistance +
            PointLightQuadraticDecay(i) * lightDistance * lightDistance);
        // Diffuse reflection
        float dotNormal = max(dot(lightDirection, normal), 0.0);
        diffuseTotal += PointLightColor(i) * matDiffuse * dotNormal * attenuation;
        // Specular reflection
        // Calculates the light reflection vector
        vec3 ref = reflect(-lightDirection, normal);
        if (dotNormal > 0.0) {
            specularTotal += PointLightColor(i) * MatSpecularColor *
                pow(max(dot(ref, camDir), 0.0), MatShininess) * attenuation;
        }
    }
#endif

#if SPOT_LIGHTS>0
    for (int i = 0; i < SPOT_LIGHTS; i++) {
        // Calculates the direction and distance from the current vertex to this spot light.
        vec3 lightDirection = SpotLightPosition(i) - vec3(position);
        float lightDistance = length(lightDirection);
        lightDirection = lightDirection / lightDistance;

        // Calculates the attenuation due to the distance of the light
        float attenuation = 1.0 / (1.0 + SpotLightLinearDecay(i) * lightDistance +
            SpotLightQuadraticDecay(i) * lightDistance * lightDistance);

        // Calculates the angle between the vertex direction and spot direction
        // If this angle is greater than the cutoff the spotlight will not contribute
        // to the final color.
        float angle = acos(dot(-lightDirection, SpotLightDirection(i)));
        float cutoff = radians(clamp(SpotLightCutoffAngle(i), 0.0, 90.0));

        if (angle < cutoff) {
            float spotFactor = pow(dot(-lightDirection, SpotLightDirection(i)), SpotLightAngularDecay(i));

            // Diffuse reflection
            float dotNormal = max(dot(lightDirection, normal), 0.0);
            diffuseTotal += SpotLightColor(i) * matDiffuse * dotNormal * attenuation * spotFactor;

            // Specular reflection
            vec3 ref = reflect(-lightDirection, normal);
            if (dotNormal > 0.0) {
                specularTotal += SpotLightColor(i) * MatSpecularColor * pow(max(dot(ref, camDir), 0.0), MatShininess) * attenuation * spotFactor;
            }
        }
    }
#endif

    // Sets output colors
    ambdiff = ambientTotal + MatEmissiveColor + diffuseTotal;
    spec = specularTotal;
}


`

const basic_fragment_source = `//
// Fragment Shader template
//

in vec3 Color;
out vec4 FragColor;

void main() {

    FragColor = vec4(Color, 1.0);
}

`

const basic_vertex_source = `//
// Vertex shader basic
//
#include <attributes>

// Model uniforms
uniform mat4 MVP;

// Final output color for fragment shader
out vec3 Color;

void main() {

    Color = VertexColor;
    gl_Position = MVP * vec4(VertexPosition, 1.0);
}


`

const panel_fragment_source = `//
// Fragment Shader template
//

// Texture uniforms
uniform sampler2D	MatTexture;
uniform vec2		MatTexinfo[3];

// Macros to access elements inside the MatTexinfo array
#define MatTexOffset		MatTexinfo[0]
#define MatTexRepeat		MatTexinfo[1]
#define MatTexFlipY	    	bool(MatTexinfo[2].x) // not used
#define MatTexVisible	    bool(MatTexinfo[2].y) // not used

// Inputs from vertex shader
in vec2 FragTexcoord;

// Input uniform
uniform vec4 Panel[8];
#define Bounds			Panel[0]		  // panel bounds in texture coordinates
#define Border			Panel[1]		  // panel border in texture coordinates
#define Padding			Panel[2]		  // panel padding in texture coordinates
#define Content			Panel[3]		  // panel content area in texture coordinates
#define BorderColor		Panel[4]		  // panel border color
#define PaddingColor	Panel[5]		  // panel padding color
#define ContentColor	Panel[6]		  // panel content color
#define TextureValid	bool(Panel[7].x)  // texture valid flag

// Output
out vec4 FragColor;


/***
* Checks if current fragment texture coordinate is inside the
* supplied rectangle in texture coordinates:
* rect[0] - position x [0,1]
* rect[1] - position y [0,1]
* rect[2] - width [0,1]
* rect[3] - height [0,1]
*/
bool checkRect(vec4 rect) {

    if (FragTexcoord.x < rect[0]) {
        return false;
    }
    if (FragTexcoord.x > rect[0] + rect[2]) {
        return false;
    }
    if (FragTexcoord.y < rect[1]) {
        return false;
    }
    if (FragTexcoord.y > rect[1] + rect[3]) {
        return false;
    }
    return true;
}


void main() {

    // Discard fragment outside of received bounds
    // Bounds[0] - xmin
    // Bounds[1] - ymin
    // Bounds[2] - xmax
    // Bounds[3] - ymax
    if (FragTexcoord.x <= Bounds[0] || FragTexcoord.x >= Bounds[2]) {
        discard;
    }
    if (FragTexcoord.y <= Bounds[1] || FragTexcoord.y >= Bounds[3]) {
        discard;
    }

    // Check if fragment is inside content area
    if (checkRect(Content)) {

        // If no texture, the color will be the material color.
        vec4 color = ContentColor;

		if (TextureValid) {
            // Adjust texture coordinates to fit texture inside the content area
            vec2 offset = vec2(-Content[0], -Content[1]);
            vec2 factor = vec2(1/Content[2], 1/Content[3]);
            vec2 texcoord = (FragTexcoord + offset) * factor;
            vec4 texColor = texture(MatTexture, texcoord * MatTexRepeat + MatTexOffset);

            // Mix content color with texture color.
            // Note that doing a simple linear interpolation (e.g. using mix()) is not correct!
            // The right formula can be found here: https://en.wikipedia.org/wiki/Alpha_compositing#Alpha_blending
            // For a more in-depth discussion: http://apoorvaj.io/alpha-compositing-opengl-blending-and-premultiplied-alpha.html#toc4

            // Pre-multiply the content color
            vec4 contentPre = ContentColor;
            contentPre.rgb *= contentPre.a;

            // Pre-multiply the texture color
            vec4 texPre = texColor;
            texPre.rgb *= texPre.a;

            // Combine colors the premultiplied final color
            color = texPre + contentPre * (1 - texPre.a);

            // Un-pre-multiply (pre-divide? :P)
            color.rgb /= color.a;
		}

        FragColor = color;
        return;
    }

    // Checks if fragment is inside paddings area
    if (checkRect(Padding)) {
        FragColor = PaddingColor;
        return;
    }

    // Checks if fragment is inside borders area
    if (checkRect(Border)) {
        FragColor = BorderColor;
        return;
    }

    // Fragment is in margins area (always transparent)
    FragColor = vec4(1,1,1,0);
}

`

const panel_vertex_source = `//
// Vertex shader panel
//
#include <attributes>

// Model uniforms
uniform mat4 ModelMatrix;

// Outputs for fragment shader
out vec2 FragTexcoord;


void main() {

    // Always flip texture coordinates
    vec2 texcoord = VertexTexcoord;
    texcoord.y = 1 - texcoord.y;
    FragTexcoord = texcoord;

    // Set position
    vec4 pos = vec4(VertexPosition.xyz, 1);
    gl_Position = ModelMatrix * pos;
}

`

const phong_fragment_source = `//
// Fragment Shader template
//

// Inputs from vertex shader
in vec4 Position;       // Vertex position in camera coordinates.
in vec3 Normal;         // Vertex normal in camera coordinates.
in vec3 CamDir;         // Direction from vertex to camera
in vec2 FragTexcoord;

#include <lights>
#include <material>
#include <phong_model>

// Final fragment color
out vec4 FragColor;

void main() {

    // Mix material color with textures colors
    vec4 texMixed = vec4(1);
    vec4 texColor;
    #if MAT_TEXTURES==1
        MIX_TEXTURE(0)
    #elif MAT_TEXTURES==2
        MIX_TEXTURE(0)
        MIX_TEXTURE(1)
    #elif MAT_TEXTURES==3
        MIX_TEXTURE(0)
        MIX_TEXTURE(1)
        MIX_TEXTURE(2)
    #endif

    // Combine material with texture colors
    vec4 matDiffuse = vec4(MatDiffuseColor, MatOpacity) * texMixed;
    vec4 matAmbient = vec4(MatAmbientColor, MatOpacity) * texMixed;

    // Inverts the fragment normal if not FrontFacing
    vec3 fragNormal = Normal;
    if (!gl_FrontFacing) {
        fragNormal = -fragNormal;
    }

    // Calculates the Ambient+Diffuse and Specular colors for this fragment using the Phong model.
    vec3 Ambdiff, Spec;
    phongModel(Position, fragNormal, CamDir, vec3(matAmbient), vec3(matDiffuse), Ambdiff, Spec);

    // Final fragment color
    FragColor = min(vec4(Ambdiff + Spec, matDiffuse.a), vec4(1.0));
}

`

const phong_vertex_source = `//
// Vertex Shader
//
#include <attributes>

// Model uniforms
uniform mat4 ModelViewMatrix;
uniform mat3 NormalMatrix;
uniform mat4 MVP;

#include <material>

// Output variables for Fragment shader
out vec4 Position;
out vec3 Normal;
out vec3 CamDir;
out vec2 FragTexcoord;

void main() {

    // Transform this vertex position to camera coordinates.
    Position = ModelViewMatrix * vec4(VertexPosition, 1.0);

    // Transform this vertex normal to camera coordinates.
    Normal = normalize(NormalMatrix * VertexNormal);

    // Calculate the direction vector from the vertex to the camera
    // The camera is at 0,0,0
    CamDir = normalize(-Position.xyz);

    // Flips texture coordinate Y if requested.
    vec2 texcoord = VertexTexcoord;
#if MAT_TEXTURES>0
    if (MatTexFlipY(0)) {
        texcoord.y = 1 - texcoord.y;
    }
#endif
    FragTexcoord = texcoord;

    gl_Position = MVP * vec4(VertexPosition, 1.0);
}

`

const physical_fragment_source = `//
// Physically Based Shading of a microfacet surface material - Fragment Shader
// Modified from reference implementation at https://github.com/KhronosGroup/glTF-WebGL-PBR
//
// References:
// [1] Real Shading in Unreal Engine 4
//     http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf
// [2] Physically Based Shading at Disney
//     http://blog.selfshadow.com/publications/s2012-shading-course/burley/s2012_pbs_disney_brdf_notes_v3.pdf
// [3] README.md - Environment Maps
//     https://github.com/KhronosGroup/glTF-WebGL-PBR/#environment-maps
// [4] "An Inexpensive BRDF Model for Physically based Rendering" by Christophe Schlick
//     https://www.cs.virginia.edu/~jdl/bib/appearance/analytic%20models/schlick94b.pdf

//#extension GL_EXT_shader_texture_lod: enable
//#extension GL_OES_standard_derivatives : enable

precision highp float;

//uniform vec3 u_LightDirection;
//uniform vec3 u_LightColor;

//#ifdef USE_IBL
//uniform samplerCube u_DiffuseEnvSampler;
//uniform samplerCube u_SpecularEnvSampler;
//uniform sampler2D u_brdfLUT;
//#endif

#ifdef HAS_BASECOLORMAP
uniform sampler2D u_BaseColorSampler;
#endif
#ifdef HAS_NORMALMAP
uniform sampler2D u_NormalSampler;
uniform float u_NormalScale;
#endif
#ifdef HAS_EMISSIVEMAP
uniform sampler2D u_EmissiveSampler;
uniform vec3 u_EmissiveFactor;
#endif
#ifdef HAS_METALROUGHNESSMAP
uniform sampler2D u_MetallicRoughnessSampler;
#endif
#ifdef HAS_OCCLUSIONMAP
uniform sampler2D u_OcclusionSampler;
uniform float u_OcclusionStrength;
#endif

// Material parameters uniform array
uniform vec4 Material[3];
// Macros to access elements inside the Material array
#define uBaseColor		    Material[0]
#define uEmissiveColor      Material[1]
#define uMetallicFactor     Material[2].x
#define uRoughnessFactor    Material[2].y

#include <lights>

// Inputs from vertex shader
in vec3 Position;       // Vertex position in camera coordinates.
in vec3 Normal;         // Vertex normal in camera coordinates.
in vec3 CamDir;         // Direction from vertex to camera
in vec2 FragTexcoord;

// Final fragment color
out vec4 FragColor;

// Encapsulate the various inputs used by the various functions in the shading equation
// We store values in this struct to simplify the integration of alternative implementations
// of the shading terms, outlined in the Readme.MD Appendix.
struct PBRInfo
{
    float NdotL;                  // cos angle between normal and light direction
    float NdotV;                  // cos angle between normal and view direction
    float NdotH;                  // cos angle between normal and half vector
    float LdotH;                  // cos angle between light direction and half vector
    float VdotH;                  // cos angle between view direction and half vector
    float perceptualRoughness;    // roughness value, as authored by the model creator (input to shader)
    float metalness;              // metallic value at the surface
    vec3 reflectance0;            // full reflectance color (normal incidence angle)
    vec3 reflectance90;           // reflectance color at grazing angle
    float alphaRoughness;         // roughness mapped to a more linear change in the roughness (proposed by [2])
    vec3 diffuseColor;            // color contribution from diffuse lighting
    vec3 specularColor;           // color contribution from specular lighting
};

const float M_PI = 3.141592653589793;
const float c_MinRoughness = 0.04;

vec4 SRGBtoLINEAR(vec4 srgbIn) {
//#ifdef MANUAL_SRGB
//    #ifdef SRGB_FAST_APPROXIMATION
//        vec3 linOut = pow(srgbIn.xyz,vec3(2.2));
//    #else //SRGB_FAST_APPROXIMATION
//        vec3 bLess = step(vec3(0.04045),srgbIn.xyz);
//        vec3 linOut = mix( srgbIn.xyz/vec3(12.92), pow((srgbIn.xyz+vec3(0.055))/vec3(1.055),vec3(2.4)), bLess );
//    #endif //SRGB_FAST_APPROXIMATION
//        return vec4(linOut,srgbIn.w);
//#else //MANUAL_SRGB
    return srgbIn;
//#endif //MANUAL_SRGB
}

// Find the normal for this fragment, pulling either from a predefined normal map
// or from the interpolated mesh normal and tangent attributes.
vec3 getNormal()
{
    // Retrieve the tangent space matrix
//#ifndef HAS_TANGENTS
    vec3 pos_dx = dFdx(Position);
    vec3 pos_dy = dFdy(Position);
    vec3 tex_dx = dFdx(vec3(FragTexcoord, 0.0));
    vec3 tex_dy = dFdy(vec3(FragTexcoord, 0.0));
    vec3 t = (tex_dy.t * pos_dx - tex_dx.t * pos_dy) / (tex_dx.s * tex_dy.t - tex_dy.s * tex_dx.t);

#ifdef HAS_NORMALS
    vec3 ng = normalize(Normal);
#else
    vec3 ng = cross(pos_dx, pos_dy);
#endif

    t = normalize(t - ng * dot(ng, t));
    vec3 b = normalize(cross(ng, t));
    mat3 tbn = mat3(t, b, ng);
//#else // HAS_TANGENTS
//    mat3 tbn = v_TBN;
//#endif

#ifdef HAS_NORMALMAP
    vec3 n = texture2D(uNormalSampler, FragTexcoord).rgb;
    n = normalize(tbn * ((2.0 * n - 1.0) * vec3(uNormalScale, uNormalScale, 1.0)));
#else
    // The tbn matrix is linearly interpolated, so we need to re-normalize
    vec3 n = normalize(tbn[2].xyz);
#endif

    return n;
}

//// Calculation of the lighting contribution from an optional Image Based Light source.
//// Precomputed Environment Maps are required uniform inputs and are computed as outlined in [1].
//// See our README.md on Environment Maps [3] for additional discussion.
//vec3 getIBLContribution(PBRInfo pbrInputs, vec3 n, vec3 reflection)
//{
//    float mipCount = 9.0; // resolution of 512x512
//    float lod = (pbrInputs.perceptualRoughness * mipCount);
//    // retrieve a scale and bias to F0. See [1], Figure 3
//    vec3 brdf = SRGBtoLINEAR(texture2D(u_brdfLUT, vec2(pbrInputs.NdotV, 1.0 - pbrInputs.perceptualRoughness))).rgb;
//    vec3 diffuseLight = SRGBtoLINEAR(textureCube(u_DiffuseEnvSampler, n)).rgb;
//
////#ifdef USE_TEX_LOD
////    vec3 specularLight = SRGBtoLINEAR(textureCubeLodEXT(u_SpecularEnvSampler, reflection, lod)).rgb;
////#else
//    vec3 specularLight = SRGBtoLINEAR(textureCube(u_SpecularEnvSampler, reflection)).rgb;
////#endif
//
//    vec3 diffuse = diffuseLight * pbrInputs.diffuseColor;
//    vec3 specular = specularLight * (pbrInputs.specularColor * brdf.x + brdf.y);
//
//    // For presentation, this allows us to disable IBL terms
//    diffuse *= u_ScaleIBLAmbient.x;
//    specular *= u_ScaleIBLAmbient.y;
//
//    return diffuse + specular;
//}

// Basic Lambertian diffuse
// Implementation from Lambert's Photometria https://archive.org/details/lambertsphotome00lambgoog
// See also [1], Equation 1
vec3 diffuse(PBRInfo pbrInputs)
{
    return pbrInputs.diffuseColor / M_PI;
}

// The following equation models the Fresnel reflectance term of the spec equation (aka F())
// Implementation of fresnel from [4], Equation 15
vec3 specularReflection(PBRInfo pbrInputs)
{
    return pbrInputs.reflectance0 + (pbrInputs.reflectance90 - pbrInputs.reflectance0) * pow(clamp(1.0 - pbrInputs.VdotH, 0.0, 1.0), 5.0);
}

// This calculates the specular geometric attenuation (aka G()),
// where rougher material will reflect less light back to the viewer.
// This implementation is based on [1] Equation 4, and we adopt their modifications to
// alphaRoughness as input as originally proposed in [2].
float geometricOcclusion(PBRInfo pbrInputs)
{
    float NdotL = pbrInputs.NdotL;
    float NdotV = pbrInputs.NdotV;
    float r = pbrInputs.alphaRoughness;

    float attenuationL = 2.0 * NdotL / (NdotL + sqrt(r * r + (1.0 - r * r) * (NdotL * NdotL)));
    float attenuationV = 2.0 * NdotV / (NdotV + sqrt(r * r + (1.0 - r * r) * (NdotV * NdotV)));
    return attenuationL * attenuationV;
}

// The following equation(s) model the distribution of microfacet normals across the area being drawn (aka D())
// Implementation from "Average Irregularity Representation of a Roughened Surface for Ray Reflection" by T. S. Trowbridge, and K. P. Reitz
// Follows the distribution function recommended in the SIGGRAPH 2013 course notes from EPIC Games [1], Equation 3.
float microfacetDistribution(PBRInfo pbrInputs)
{
    float roughnessSq = pbrInputs.alphaRoughness * pbrInputs.alphaRoughness;
    float f = (pbrInputs.NdotH * roughnessSq - pbrInputs.NdotH) * pbrInputs.NdotH + 1.0;
    return roughnessSq / (M_PI * f * f);
}

void main() {

    float perceptualRoughness = uRoughnessFactor;
    float metallic = uMetallicFactor;

#ifdef HAS_METALROUGHNESSMAP
    // Roughness is stored in the 'g' channel, metallic is stored in the 'b' channel.
    // This layout intentionally reserves the 'r' channel for (optional) occlusion map data
    vec4 mrSample = texture2D(uMetallicRoughnessSampler, FragTexcoord);
    perceptualRoughness = mrSample.g * perceptualRoughness;
    metallic = mrSample.b * metallic;
#endif

    perceptualRoughness = clamp(perceptualRoughness, c_MinRoughness, 1.0);
    metallic = clamp(metallic, 0.0, 1.0);
    // Roughness is authored as perceptual roughness; as is convention,
    // convert to material roughness by squaring the perceptual roughness [2].
    float alphaRoughness = perceptualRoughness * perceptualRoughness;

    // The albedo may be defined from a base texture or a flat color
#ifdef HAS_BASECOLORMAP
    vec4 baseColor = SRGBtoLINEAR(texture2D(uBaseColorSampler, FragTexcoord)) * uBaseColor;
#else
    vec4 baseColor = uBaseColor;
#endif

    vec3 f0 = vec3(0.04);
    vec3 diffuseColor = baseColor.rgb * (vec3(1.0) - f0);
    diffuseColor *= 1.0 - metallic;
    vec3 specularColor = mix(f0, baseColor.rgb, uMetallicFactor);

    // Compute reflectance.
    float reflectance = max(max(specularColor.r, specularColor.g), specularColor.b);

    // For typical incident reflectance range (between 4% to 100%) set the grazing reflectance to 100% for typical fresnel effect.
    // For very low reflectance range on highly diffuse objects (below 4%), incrementally reduce grazing reflecance to 0%.
    float reflectance90 = clamp(reflectance * 25.0, 0.0, 1.0);
    vec3 specularEnvironmentR0 = specularColor.rgb;
    vec3 specularEnvironmentR90 = vec3(1.0, 1.0, 1.0) * reflectance90;

    // TODO These are not currently uniforms - and need to support all kinds of lights!
    vec3 u_LightColor = vec3(1,1,1);
    vec3 u_LightDirection = vec3(1,0,0);

    vec3 n = getNormal();                             // normal at surface point
    vec3 v = normalize(CamDir);                       // Vector from surface point to camera
    vec3 l = normalize(u_LightDirection);             // Vector from surface point to light
    vec3 h = normalize(l+v);                          // Half vector between both l and v
    vec3 reflection = -normalize(reflect(v, n));

    float NdotL = clamp(dot(n, l), 0.001, 1.0);
    float NdotV = abs(dot(n, v)) + 0.001;
    float NdotH = clamp(dot(n, h), 0.0, 1.0);
    float LdotH = clamp(dot(l, h), 0.0, 1.0);
    float VdotH = clamp(dot(v, h), 0.0, 1.0);

    PBRInfo pbrInputs = PBRInfo(
        NdotL,
        NdotV,
        NdotH,
        LdotH,
        VdotH,
        perceptualRoughness,
        metallic,
        specularEnvironmentR0,
        specularEnvironmentR90,
        alphaRoughness,
        diffuseColor,
        specularColor
    );

    // Calculate the shading terms for the microfacet specular shading model
    vec3 F = specularReflection(pbrInputs);
    float G = geometricOcclusion(pbrInputs);
    float D = microfacetDistribution(pbrInputs);

    // Calculation of analytical lighting contribution
    vec3 diffuseContrib = (1.0 - F) * diffuse(pbrInputs);
    vec3 specContrib = F * G * D / (4.0 * NdotL * NdotV);
    // Obtain final intensity as reflectance (BRDF) scaled by the energy of the light (cosine law)
    vec3 color = NdotL * u_LightColor * (diffuseContrib + specContrib);

    // Calculate lighting contribution from image based lighting source (IBL)
//#ifdef USE_IBL
//    color += getIBLContribution(pbrInputs, n, reflection);
//#endif

    // Apply optional PBR terms for additional (optional) shading
#ifdef HAS_OCCLUSIONMAP
    float ao = texture2D(uOcclusionSampler, v_UV).r;
    color = mix(color, color * ao, u_OcclusionStrength);
#endif

#ifdef HAS_EMISSIVEMAP
    vec3 emissive = SRGBtoLINEAR(texture2D(u_EmissiveSampler, v_UV)).rgb * u_EmissiveFactor;
    color += emissive;
#endif

    // Final fragment color
    FragColor = vec4(pow(color,vec3(1.0/2.2)), baseColor.a);

}


`

const physical_vertex_source = `//
// Physically Based Shading of a microfacet surface material - Vertex Shader
// Modified from reference implementation at https://github.com/KhronosGroup/glTF-WebGL-PBR
//
#include <attributes>

// Model uniforms
uniform mat4 ModelViewMatrix;
uniform mat3 NormalMatrix;
uniform mat4 MVP;

// Output variables for Fragment shader
out vec3 Position;
out vec3 Normal;
out vec3 CamDir;
out vec2 FragTexcoord;

void main() {

    // Transform this vertex position to camera coordinates.
    Position = vec3(ModelViewMatrix * vec4(VertexPosition, 1.0));

    // Transform this vertex normal to camera coordinates.
    Normal = normalize(NormalMatrix * VertexNormal);

    // Calculate the direction vector from the vertex to the camera
    // The camera is at 0,0,0
    CamDir = normalize(-Position.xyz);

    // Flips texture coordinate Y if requested.
    vec2 texcoord = VertexTexcoord;
    // #if MAT_TEXTURES>0
    //     if (MatTexFlipY(0)) {
    //         texcoord.y = 1 - texcoord.y;
    //     }
    // #endif
    FragTexcoord = texcoord;

    gl_Position = MVP * vec4(VertexPosition, 1.0);
}


`

const point_fragment_source = `#include <material>

// GLSL 3.30 does not allow indexing texture sampler with non constant values.
// This macro is used to mix the texture with the specified index with the material color.
// It should be called for each texture index.
#define MIX_POINT_TEXTURE(i)                                                                                     \
    if (MatTexVisible(i)) {                                                                                      \
        vec2 pt = gl_PointCoord - vec2(0.5);                                                                     \
        vec4 texColor = texture(MatTexture[i], (Rotation * pt + vec2(0.5)) * MatTexRepeat(i) + MatTexOffset(i)); \
        if (i == 0) {                                                                                            \
            texMixed = texColor;                                                                                 \
        } else {                                                                                                 \
            texMixed = mix(texMixed, texColor, texColor.a);                                                      \
        }                                                                                                        \
    }

// Inputs from vertex shader
in vec3 Color;
flat in mat2 Rotation;

// Output
out vec4 FragColor;

void main() {

    // Mix material color with textures colors
    vec4 texMixed = vec4(1);
    #if MAT_TEXTURES==1
        MIX_POINT_TEXTURE(0)
    #elif MAT_TEXTURES==2
        MIX_POINT_TEXTURE(0)
        MIX_POINT_TEXTURE(1)
    #elif MAT_TEXTURES==3
        MIX_POINT_TEXTURE(0)
        MIX_POINT_TEXTURE(1)
        MIX_POINT_TEXTURE(2)
    #endif

    // Generates final color
    FragColor = min(vec4(Color, MatOpacity) * texMixed, vec4(1));
}

`

const point_vertex_source = `#include <attributes>

// Model uniforms
uniform mat4 MVP;

// Material uniforms
#include <material>

// Outputs for fragment shader
out vec3 Color;
flat out mat2 Rotation;

void main() {

    // Rotation matrix for fragment shader
    float rotSin = sin(MatPointRotationZ);
    float rotCos = cos(MatPointRotationZ);
    Rotation = mat2(rotCos, rotSin, - rotSin, rotCos);

    // Sets the vertex position
    vec4 pos = MVP * vec4(VertexPosition, 1.0);
    gl_Position = pos;

    // Sets the size of the rasterized point decreasing with distance
    gl_PointSize = (1.0 - pos.z / pos.w) * MatPointSize;

    // Outputs color
    Color = MatEmissiveColor;
}

`

const sprite_fragment_source = `//
// Fragment shader for sprite
//

#include <material>

// Inputs from vertex shader
in vec3 Color;
in vec2 FragTexcoord;

// Output
out vec4 FragColor;

void main() {

    // Combine all texture colors and opacity
    vec4 texCombined = vec4(1);
#if MAT_TEXTURES>0
    for (int i = 0; i < {{.MatTexturesMax}}; i++) {
        vec4 texcolor = texture(MatTexture[i], FragTexcoord * MatTexRepeat(i) + MatTexOffset(i));
        if (i == 0) {
            texCombined = texcolor;
        } else {
            texCombined = mix(texCombined, texcolor, texcolor.a);
        }
    }
#endif

    // Combine material color with texture
    FragColor = min(vec4(Color, MatOpacity) * texCombined, vec4(1));
}

`

const sprite_vertex_source = `//
// Vertex shader for sprites
//

#include <attributes>

// Input uniforms
uniform mat4 MVP;

#include <material>

// Outputs for fragment shader
out vec3 Color;
out vec2 FragTexcoord;

void main() {

    // Applies transformation to vertex position
    gl_Position = MVP * vec4(VertexPosition, 1.0);

    // Outputs color
    Color = MatDiffuseColor;

    // Flips texture coordinate Y if requested.
    vec2 texcoord = VertexTexcoord;
#if MAT_TEXTURES>0
    if (MatTexFlipY[0]) {
        texcoord.y = 1 - texcoord.y;
    }
#endif
    FragTexcoord = texcoord;
}

`

const standard_fragment_source = `//
// Fragment Shader template
//
#include <material>

// Inputs from Vertex shader
in vec3 ColorFrontAmbdiff;
in vec3 ColorFrontSpec;
in vec3 ColorBackAmbdiff;
in vec3 ColorBackSpec;
in vec2 FragTexcoord;

// Output
out vec4 FragColor;


void main() {

    // Mix material color with textures colors
    vec4 texMixed = vec4(1);
    vec4 texColor;
    #if MAT_TEXTURES==1
        MIX_TEXTURE(0)
    #elif MAT_TEXTURES==2
        MIX_TEXTURE(0)
        MIX_TEXTURE(1)
    #elif MAT_TEXTURES==3
        MIX_TEXTURE(0)
        MIX_TEXTURE(1)
        MIX_TEXTURE(2)
    #endif

    vec4 colorAmbDiff;
    vec4 colorSpec;
    if (gl_FrontFacing) {
        colorAmbDiff = vec4(ColorFrontAmbdiff, MatOpacity);
        colorSpec = vec4(ColorFrontSpec, 0);
    } else {
        colorAmbDiff = vec4(ColorBackAmbdiff, MatOpacity);
        colorSpec = vec4(ColorBackSpec, 0);
    }
    FragColor = min(colorAmbDiff * texMixed + colorSpec, vec4(1));
}

`

const standard_vertex_source = `//
// Vertex shader standard
//
#include <attributes>

// Model uniforms
uniform mat4 ModelViewMatrix;
uniform mat3 NormalMatrix;
uniform mat4 MVP;

#include <lights>
#include <material>
#include <phong_model>


// Outputs for the fragment shader.
out vec3 ColorFrontAmbdiff;
out vec3 ColorFrontSpec;
out vec3 ColorBackAmbdiff;
out vec3 ColorBackSpec;
out vec2 FragTexcoord;

void main() {

    // Transform this vertex normal to camera coordinates.
    vec3 normal = normalize(NormalMatrix * VertexNormal);

    // Calculate this vertex position in camera coordinates
    vec4 position = ModelViewMatrix * vec4(VertexPosition, 1.0);

    // Calculate the direction vector from the vertex to the camera
    // The camera is at 0,0,0
    vec3 camDir = normalize(-position.xyz);

    // Calculates the vertex Ambient+Diffuse and Specular colors using the Phong model
    // for the front and back
    phongModel(position,  normal, camDir, MatAmbientColor, MatDiffuseColor, ColorFrontAmbdiff, ColorFrontSpec);
    phongModel(position, -normal, camDir, MatAmbientColor, MatDiffuseColor, ColorBackAmbdiff, ColorBackSpec);

    vec2 texcoord = VertexTexcoord;
#if MAT_TEXTURES > 0
    // Flips texture coordinate Y if requested.
    if (MatTexFlipY(0)) {
        texcoord.y = 1 - texcoord.y;
    }
#endif
    FragTexcoord = texcoord;

    gl_Position = MVP * vec4(VertexPosition, 1.0);
}

`

// Maps include name with its source code
var includeMap = map[string]string{

	"attributes":  include_attributes_source,
	"lights":      include_lights_source,
	"material":    include_material_source,
	"phong_model": include_phong_model_source,
}

// Maps shader name with its source code
var shaderMap = map[string]string{

	"basic_fragment":    basic_fragment_source,
	"basic_vertex":      basic_vertex_source,
	"panel_fragment":    panel_fragment_source,
	"panel_vertex":      panel_vertex_source,
	"phong_fragment":    phong_fragment_source,
	"phong_vertex":      phong_vertex_source,
	"physical_fragment": physical_fragment_source,
	"physical_vertex":   physical_vertex_source,
	"point_fragment":    point_fragment_source,
	"point_vertex":      point_vertex_source,
	"sprite_fragment":   sprite_fragment_source,
	"sprite_vertex":     sprite_vertex_source,
	"standard_fragment": standard_fragment_source,
	"standard_vertex":   standard_vertex_source,
}

// Maps program name with Proginfo struct with shaders names
var programMap = map[string]ProgramInfo{

	"basic":    {"basic_vertex", "basic_fragment", ""},
	"panel":    {"panel_vertex", "panel_fragment", ""},
	"phong":    {"phong_vertex", "phong_fragment", ""},
	"physical": {"physical_vertex", "physical_fragment", ""},
	"point":    {"point_vertex", "point_fragment", ""},
	"sprite":   {"sprite_vertex", "sprite_fragment", ""},
	"standard": {"standard_vertex", "standard_fragment", ""},
}