java - 如何实现 PBR 着色器 - LWJGL？

Question

我一直在关注 Thinmatrix 教程来练习 GLSL 和矢量数学，现在我正在尝试实现一个 PBR 着色器，我从这里 (learnOpenGL)借来。我首先确保模型不会渲染。我的旧兰伯特着色器工作正常，但实现着色器一直很棘手。否则我将不得不将 c++ 代码逐块移植到 java，虽然我想尝试一段时间，但我想在我现有的引擎中实现一个 PBR 着色器。我相信我已经启动了这些属性：

@Override
    protected void bindAttributes() {
        super.bindAttribute(0, "aPos");
        super.bindAttribute(1, "aTexCoords");
        super.bindAttribute(2, "aNormal");
    }

但不确定我应该如何添加制服，此时我正在黑暗中尝试一下。我注意到着色器有一个 mat4 统一视图、mat4 统一 camPos 和 mat4 统一模型，我没有在 LWJGL 中绑定（请原谅我的术语不好）。目前我的制服是：

@Override
protected void getAllUniformLocations() {
    location_transformationMatrix = super.getUniformLocation("transformationMatrix");
    location_projectionMatrix = super.getUniformLocation("projection");
    location_viewMatrix = super.getUniformLocation("view");
    location_shineDamper = super.getUniformLocation("shineDamper");
    location_reflectivity = super.getUniformLocation("reflectivity");
    location_useFakeLighting = super.getUniformLocation("useFakeLighting");
    location_skyColour = super.getUniformLocation("skyColour");
    location_numberOfRows = super.getUniformLocation("numberOfRows");
    location_offset = super.getUniformLocation("offset");
    location_lightPosition = new int[MAX_LIGHTS];
    location_lightColour = new int[MAX_LIGHTS];
    location_attenuation = new int [MAX_LIGHTS];
    for(int i=0;i<MAX_LIGHTS;i++) {
        location_lightPosition[i] = super.getUniformLocation("lightPositions[" + i + "]");
        location_lightColour[i] = super.getUniformLocation("lightColors[" + i + "]");
}

来自 learnOpengl 的顶点着色器：

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec2 aTexCoords;
layout (location = 2) in vec3 aNormal;

out vec2 TexCoords;
out vec3 WorldPos;
out vec3 Normal;

uniform mat4 projection;
uniform mat4 view;
uniform mat4 model;

void main()
{
    TexCoords = aTexCoords;
    WorldPos = vec3(model * vec4(aPos, 1.0));
    Normal = mat3(model) * aNormal;   

    gl_Position =  projection * view * vec4(WorldPos, 1.0);
}

来自learnopengl的片段着色器：

#version 330 core
out vec4 FragColor;
in vec2 TexCoords;
in vec3 WorldPos;
in vec3 Normal;

// material parameters
uniform sampler2D albedoMap;
uniform sampler2D normalMap;
uniform sampler2D metallicMap;
uniform sampler2D roughnessMap;
uniform sampler2D aoMap;

// lights
uniform vec3 lightPositions[4];
uniform vec3 lightColors[4];

uniform vec3 camPos;

const float PI = 3.14159265359;
// ----------------------------------------------------------------------------
// Easy trick to get tangent-normals to world-space to keep PBR code simplified.
// Don't worry if you don't get what's going on; you generally want to do normal 
// mapping the usual way for performance anways; I do plan make a note of this 
// technique somewhere later in the normal mapping tutorial.
vec3 getNormalFromMap()
{
    vec3 tangentNormal = texture(normalMap, TexCoords).xyz * 2.0 - 1.0;

    vec3 Q1  = dFdx(WorldPos);
    vec3 Q2  = dFdy(WorldPos);
    vec2 st1 = dFdx(TexCoords);
    vec2 st2 = dFdy(TexCoords);

    vec3 N   = normalize(Normal);
    vec3 T  = normalize(Q1*st2.t - Q2*st1.t);
    vec3 B  = -normalize(cross(N, T));
    mat3 TBN = mat3(T, B, N);

    return normalize(TBN * tangentNormal);
}
// ----------------------------------------------------------------------------
float DistributionGGX(vec3 N, vec3 H, float roughness)
{
    float a = roughness*roughness;
    float a2 = a*a;
    float NdotH = max(dot(N, H), 0.0);
    float NdotH2 = NdotH*NdotH;

    float nom   = a2;
    float denom = (NdotH2 * (a2 - 1.0) + 1.0);
    denom = PI * denom * denom;

    return nom / denom;
}
// ----------------------------------------------------------------------------
float GeometrySchlickGGX(float NdotV, float roughness)
{
    float r = (roughness + 1.0);
    float k = (r*r) / 8.0;

    float nom   = NdotV;
    float denom = NdotV * (1.0 - k) + k;

    return nom / denom;
}
// ----------------------------------------------------------------------------
float GeometrySmith(vec3 N, vec3 V, vec3 L, float roughness)
{
    float NdotV = max(dot(N, V), 0.0);
    float NdotL = max(dot(N, L), 0.0);
    float ggx2 = GeometrySchlickGGX(NdotV, roughness);
    float ggx1 = GeometrySchlickGGX(NdotL, roughness);

    return ggx1 * ggx2;
}
// ----------------------------------------------------------------------------
vec3 fresnelSchlick(float cosTheta, vec3 F0)
{
    return F0 + (1.0 - F0) * pow(1.0 - cosTheta, 5.0);
}
// ----------------------------------------------------------------------------
void main()
{       
    vec3 albedo     = pow(texture(albedoMap, TexCoords).rgb, vec3(2.2));
    float metallic  = texture(metallicMap, TexCoords).r;
    float roughness = texture(roughnessMap, TexCoords).r;
    float ao        = texture(aoMap, TexCoords).r;

    vec3 N = getNormalFromMap();
    vec3 V = normalize(camPos - WorldPos);

    // calculate reflectance at normal incidence; if dia-electric (like plastic) use F0 
    // of 0.04 and if it's a metal, use the albedo color as F0 (metallic workflow)    
    vec3 F0 = vec3(0.04); 
    F0 = mix(F0, albedo, metallic);

    // reflectance equation
    vec3 Lo = vec3(0.0);
    for(int i = 0; i < 4; ++i) 
    {
        // calculate per-light radiance
        vec3 L = normalize(lightPositions[i] - WorldPos);
        vec3 H = normalize(V + L);
        float distance = length(lightPositions[i] - WorldPos);
        float attenuation = 1.0 / (distance * distance);
        vec3 radiance = lightColors[i] * attenuation;

        // Cook-Torrance BRDF
        float NDF = DistributionGGX(N, H, roughness);   
        float G   = GeometrySmith(N, V, L, roughness);      
        vec3 F    = fresnelSchlick(max(dot(H, V), 0.0), F0);

        vec3 nominator    = NDF * G * F; 
        float denominator = 4 * max(dot(N, V), 0.0) * max(dot(N, L), 0.0) + 0.001; // 0.001 to prevent divide by zero.
        vec3 specular = nominator / denominator;

        // kS is equal to Fresnel
        vec3 kS = F;
        // for energy conservation, the diffuse and specular light can't
        // be above 1.0 (unless the surface emits light); to preserve this
        // relationship the diffuse component (kD) should equal 1.0 - kS.
        vec3 kD = vec3(1.0) - kS;
        // multiply kD by the inverse metalness such that only non-metals 
        // have diffuse lighting, or a linear blend if partly metal (pure metals
        // have no diffuse light).
        kD *= 1.0 - metallic;     

        // scale light by NdotL
        float NdotL = max(dot(N, L), 0.0);        

        // add to outgoing radiance Lo
        Lo += (kD * albedo / PI + specular) * radiance * NdotL;  // note that we already multiplied the BRDF by the Fresnel (kS) so we won't multiply by kS again
    }   

    // ambient lighting (note that the next IBL tutorial will replace 
    // this ambient lighting with environment lighting).
    vec3 ambient = vec3(0.03) * albedo * ao;

    vec3 color = ambient + Lo;

    // HDR tonemapping
    color = color / (color + vec3(1.0));
    // gamma correct
    color = pow(color, vec3(1.0/2.2)); 

    FragColor = vec4(color, 1.0);
}

我注意到它们是我没有在 lwjgl 中绑定的制服，有些我不确定如何启动或为什么需要这样做（统一 mat4 模型）。我想我可以离开 Thinmatrix 教程中的制服，并假设它不会处理。如果我错了，请纠正我。

对制作此过程的任何见解将不胜感激。我一直在观看有关 PBR 的讲座和基于着色玩具的视频。

这是我基于thinmatrix教程的代码：这里

更新：这很接近，但现在我正在尝试纹理，反照率看起来很暗，而其他的则无法区分。我也不知道我应该用 camPos 制服做什么，或者它是否有必要。