basic PBR example (#3621)

* basic pbr example

pbr implementation  includes rpbr.h and few shader files header only file, which self contain everything needed for pbr rendering. Few textures and one model of the car which is under free licence which is included inside basic_pbr.c example file  currently supported shader versions are 120 and 330 , version 100 has small issue which I have to resolve

* Unloading PBRMAterial

I forgot unloading PBRMaterial

* fix small issue with texOffset assigment.

value was Vector4 at first but I found out it would be unclear for and users, so I change to have two Vector2 instead, but forgot to assign offset .

* Changed size of textures and file name changed

Changed size of textures from 2048x2048 to 1024x1024 and file name changed to shaders_basic_pbr.c ,
Added the function PBRModel PBRModelLoadFromMesh(Mesh mesh);
but GenMeshPlane(2, 2.0, 3, 3) culdn't be used because it crash once GenMeshTangents() is used with that plane mesh

examples/shaders/resources/shaders/glsl100/pbr.fs

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+#version 100
+
+precision mediump float;
+
+#define MAX_LIGHTS              4
+#define LIGHT_DIRECTIONAL       0
+#define LIGHT_POINT             1
+#define PI 3.14159265358979323846
+
+struct Light {
+    int enabled;
+    int type;
+    vec3 position;
+    vec3 target;
+    vec4 color;
+    float intensity;
+};
+
+// Input vertex attributes (from vertex shader)
+varying in vec3 fragPosition;
+varying in vec2 fragTexCoord;
+varying in vec4 fragColor;
+varying in vec3 fragNormal;
+varying in vec4 shadowPos;
+varying in mat3 TBN;
+
+
+// Input uniform values
+uniform int numOfLights;
+uniform sampler2D albedoMap;
+uniform sampler2D mraMap;
+uniform sampler2D normalMap;
+uniform sampler2D emissiveMap; // r: Hight g:emissive
+
+uniform vec2 tiling;
+uniform vec2 offset;
+
+uniform int useTexAlbedo;
+uniform int useTexNormal;
+uniform int useTexMRA;
+uniform int useTexEmissive;
+
+uniform vec4  albedoColor;
+uniform vec4  emissiveColor;
+uniform float normalValue;
+uniform float metallicValue;
+uniform float roughnessValue;
+uniform float aoValue;
+uniform float emissivePower;
+
+// Input lighting values
+uniform Light lights[MAX_LIGHTS];
+uniform vec3 viewPos;
+
+uniform vec3 ambientColor;
+uniform float ambient;
+
+// refl in range  0 to 1
+// returns base reflectivity to 1
+// incrase reflectivity when surface view at larger angle
+vec3 schlickFresnel(float hDotV,vec3 refl)
+{
+        return refl + (1.0 - refl) * pow(1.0 - hDotV,5.0);
+}
+
+float ggxDistribution(float nDotH,float roughness)
+{
+        float a = roughness * roughness * roughness * roughness;
+        float d = nDotH * nDotH * (a - 1.0) + 1.0;
+        d = PI * d * d;
+        return a / max(d,0.0000001);
+}
+
+float geomSmith(float nDotV,float nDotL,float roughness)
+{
+        float r = roughness + 1.0;
+        float k = r * r / 8.0;
+        float ik = 1.0 - k;
+        float ggx1 = nDotV / (nDotV * ik + k);
+        float ggx2 = nDotL / (nDotL * ik + k);
+        return ggx1 * ggx2;
+}
+
+vec3 pbr(){
+        vec3 albedo = texture2D(albedoMap,vec2(fragTexCoord.x*tiling.x+offset.x,fragTexCoord.y*tiling.y+offset.y)).rgb;
+        albedo = vec3(albedoColor.x*albedo.x,albedoColor.y*albedo.y,albedoColor.z*albedo.z);
+        float metallic = clamp(metallicValue,0.0,1.0);
+        float roughness = clamp(roughnessValue,0.0,1.0);
+        float ao = clamp(aoValue,0.0,1.0);
+        if(useTexMRA == 1) {
+            vec4 mra = texture2D(mraMap, vec2(fragTexCoord.x * tiling.x + offset.x, fragTexCoord.y * tiling.y + offset.y));
+            metallic = clamp(mra.r+metallicValue,0.04,1.0);
+            roughness = clamp(mra.g+roughnessValue,0.04,1.0);
+            ao = (mra.b+aoValue)*0.5;
+        }
+
+
+
+        vec3 N = normalize(fragNormal);
+        if(useTexNormal == 1) {
+            N = texture2D(normalMap, vec2(fragTexCoord.x * tiling.x + offset.y, fragTexCoord.y * tiling.y + offset.y)).rgb;
+            N = normalize(N * 2.0 - 1.0);
+            N = normalize(N * TBN);
+        }
+
+        vec3 V = normalize(viewPos - fragPosition);
+
+        vec3 e = vec3(0);
+        e = (texture2D(emissiveMap, vec2(fragTexCoord.x*tiling.x+offset.x, fragTexCoord.y*tiling.y+offset.y)).rgb).g * emissiveColor.rgb*emissivePower * float(useTexEmissive);
+
+        //return N;//vec3(metallic,metallic,metallic);
+        //if  dia-electric use base reflectivity of 0.04 otherwise ut is a metal use albedo as base reflectivity
+        vec3 baseRefl = mix(vec3(0.04),albedo.rgb,metallic);
+        vec3 Lo = vec3(0.0);  // acumulate lighting lum
+
+        for(int i=0;i<numOfLights;++i){
+
+            vec3 L = normalize(lights[i].position - fragPosition);  // calc light vector
+            vec3 H = normalize(V + L);                              // calc halfway bisecting vector
+            float dist = length(lights[i].position - fragPosition); // calc distance to light
+            float attenuation = 1.0 / (dist * dist * 0.23);                // calc attenuation
+            vec3 radiance = lights[i].color.rgb * lights[i].intensity * attenuation;         // calc input radiance,light energy comming in
+
+            //Cook-Torrance BRDF distribution function
+            float nDotV = max(dot(N,V),0.0000001);
+            float nDotL = max(dot(N,L),0.0000001);
+            float hDotV = max(dot(H,V),0.0);
+            float nDotH = max(dot(N,H),0.0);
+            float D = ggxDistribution(nDotH,roughness); // larger the more micro-facets aligned to H
+            float G = geomSmith(nDotV,nDotL,roughness); // smaller the more micro-facets shadow
+            vec3 F = schlickFresnel(hDotV, baseRefl);  // fresnel proportion of specular reflectance
+
+            vec3 spec = (D * G * F) / (4.0 * nDotV * nDotL);
+            // difuse and spec light can't be above 1.0
+            // kD = 1.0 - kS  diffuse component is equal 1.0 - spec comonent
+            vec3 kD = vec3(1.0) - F;
+            //mult kD by the inverse of metallnes , only non-metals should have diffuse light
+            kD *= 1.0 - metallic;
+            Lo += ((kD * albedo.rgb / PI + spec) * radiance * nDotL)*float(lights[i].enabled); // angle of light has impact on result
+        }
+        vec3 ambient_final = (ambientColor + albedo)* ambient * 0.5;
+        return ambient_final+Lo*ao+e;
+}
+
+void main()
+{
+       vec3 color = pbr();
+
+        //HDR tonemapping
+        color = pow(color,color + vec3(1.0));
+        //gamma correction
+        color = pow(color,vec3(1.0/2.2));
+
+        gl_FragColor = vec4(color,1.0);
+
+}

examples/shaders/resources/shaders/glsl100/pbr.vs

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+#version 100
+
+// Input vertex attributes
+attribute  vec3 vertexPosition;
+attribute  vec2 vertexTexCoord;
+attribute  vec3 vertexNormal;
+attribute  vec3 vertexTangent;
+attribute  vec4 vertexColor;
+
+// Input uniform values
+uniform mat4 mvp;
+uniform mat4 matModel;
+uniform mat4 matNormal;
+uniform vec3 lightPos;
+uniform vec4 difColor;
+
+// Output vertex attributes (to fragment shader)
+varying vec3 fragPosition;
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+varying vec3 fragNormal;
+varying mat3 TBN;
+
+const float normalOffset = 0.1;
+
+// https://github.com/glslify/glsl-inverse
+mat3 inverse(mat3 m)
+{
+  float a00 = m[0][0], a01 = m[0][1], a02 = m[0][2];
+  float a10 = m[1][0], a11 = m[1][1], a12 = m[1][2];
+  float a20 = m[2][0], a21 = m[2][1], a22 = m[2][2];
+
+  float b01 = a22*a11 - a12*a21;
+  float b11 = -a22*a10 + a12*a20;
+  float b21 = a21*a10 - a11*a20;
+
+  float det = a00*b01 + a01*b11 + a02*b21;
+
+  return mat3(b01, (-a22*a01 + a02*a21), (a12*a01 - a02*a11),
+              b11, (a22*a00 - a02*a20), (-a12*a00 + a02*a10),
+              b21, (-a21*a00 + a01*a20), (a11*a00 - a01*a10))/det;
+}
+
+// https://github.com/glslify/glsl-transpose
+mat3 transpose(mat3 m)
+{
+  return mat3(m[0][0], m[1][0], m[2][0],
+              m[0][1], m[1][1], m[2][1],
+              m[0][2], m[1][2], m[2][2]);
+}
+
+void main()
+{
+
+    // calc binormal from vertex normal and tangent
+    vec3 vertexBinormal = cross(vertexNormal, vertexTangent);
+    // calc fragment normal based on normal transformations
+    mat3 normalMatrix = transpose(inverse(mat3(matModel)));
+    // calc fragment position based on model transformations
+
+    fragPosition = vec3(matModel*vec4(vertexPosition, 1.0));
+
+    fragTexCoord = vertexTexCoord*2.0;
+
+    fragNormal = normalize(normalMatrix*vertexNormal);
+    vec3 fragTangent = normalize(normalMatrix*vertexTangent);
+    fragTangent = normalize(fragTangent - dot(fragTangent, fragNormal)*fragNormal);
+    vec3 fragBinormal = normalize(normalMatrix*vertexBinormal);
+    fragBinormal = cross(fragNormal, fragTangent);
+
+    TBN = transpose(mat3(fragTangent, fragBinormal, fragNormal));
+
+    // Calculate final vertex position
+    gl_Position = mvp * vec4(vertexPosition, 1.0);
+}

examples/shaders/resources/shaders/glsl120/pbr.fs

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+#version 120
+
+precision mediump float;
+
+#define MAX_LIGHTS              4
+#define LIGHT_DIRECTIONAL       0
+#define LIGHT_POINT             1
+#define PI 3.14159265358979323846
+
+struct Light {
+    int enabled;
+    int type;
+    vec3 position;
+    vec3 target;
+    vec4 color;
+    float intensity;
+};
+
+// Input vertex attributes (from vertex shader)
+varying in vec3 fragPosition;
+varying in vec2 fragTexCoord;
+varying in vec4 fragColor;
+varying in vec3 fragNormal;
+varying in vec4 shadowPos;
+varying in mat3 TBN;
+
+
+// Input uniform values
+uniform int numOfLights;
+uniform sampler2D albedoMap;
+uniform sampler2D mraMap;
+uniform sampler2D normalMap;
+uniform sampler2D emissiveMap; // r: Hight g:emissive
+
+uniform vec2 tiling;
+uniform vec2 offset;
+
+uniform int useTexAlbedo;
+uniform int useTexNormal;
+uniform int useTexMRA;
+uniform int useTexEmissive;
+
+uniform vec4  albedoColor;
+uniform vec4  emissiveColor;
+uniform float normalValue;
+uniform float metallicValue;
+uniform float roughnessValue;
+uniform float aoValue;
+uniform float emissivePower;
+
+// Input lighting values
+uniform Light lights[MAX_LIGHTS];
+uniform vec3 viewPos;
+
+uniform vec3 ambientColor;
+uniform float ambient;
+
+// refl in range  0 to 1
+// returns base reflectivity to 1
+// incrase reflectivity when surface view at larger angle
+vec3 schlickFresnel(float hDotV,vec3 refl)
+{
+        return refl + (1.0 - refl) * pow(1.0 - hDotV,5.0);
+}
+
+float ggxDistribution(float nDotH,float roughness)
+{
+        float a = roughness * roughness * roughness * roughness;
+        float d = nDotH * nDotH * (a - 1.0) + 1.0;
+        d = PI * d * d;
+        return a / max(d,0.0000001);
+}
+
+float geomSmith(float nDotV,float nDotL,float roughness)
+{
+        float r = roughness + 1.0;
+        float k = r * r / 8.0;
+        float ik = 1.0 - k;
+        float ggx1 = nDotV / (nDotV * ik + k);
+        float ggx2 = nDotL / (nDotL * ik + k);
+        return ggx1 * ggx2;
+}
+
+vec3 pbr(){
+        vec3 albedo = texture2D(albedoMap,vec2(fragTexCoord.x*tiling.x+offset.x,fragTexCoord.y*tiling.y+offset.y)).rgb;
+        albedo = vec3(albedoColor.x*albedo.x,albedoColor.y*albedo.y,albedoColor.z*albedo.z);
+        float metallic = clamp(metallicValue,0.0,1.0);
+        float roughness = clamp(roughnessValue,0.0,1.0);
+        float ao = clamp(aoValue,0.0,1.0);
+        if(useTexMRA == 1) {
+            vec4 mra = texture2D(mraMap, vec2(fragTexCoord.x * tiling.x + offset.x, fragTexCoord.y * tiling.y + offset.y));
+            metallic = clamp(mra.r+metallicValue,0.04,1.0);
+            roughness = clamp(mra.g+roughnessValue,0.04,1.0);
+            ao = (mra.b+aoValue)*0.5;
+        }
+
+
+
+        vec3 N = normalize(fragNormal);
+        if(useTexNormal == 1) {
+            N = texture2D(normalMap, vec2(fragTexCoord.x * tiling.x + offset.y, fragTexCoord.y * tiling.y + offset.y)).rgb;
+            N = normalize(N * 2.0 - 1.0);
+            N = normalize(N * TBN);
+        }
+
+        vec3 V = normalize(viewPos - fragPosition);
+
+        vec3 e = vec3(0);
+        e = (texture2D(emissiveMap, vec2(fragTexCoord.x*tiling.x+offset.x, fragTexCoord.y*tiling.y+offset.y)).rgb).g * emissiveColor.rgb*emissivePower * float(useTexEmissive);
+
+        //return N;//vec3(metallic,metallic,metallic);
+        //if  dia-electric use base reflectivity of 0.04 otherwise ut is a metal use albedo as base reflectivity
+        vec3 baseRefl = mix(vec3(0.04),albedo.rgb,metallic);
+        vec3 Lo = vec3(0.0);  // acumulate lighting lum
+
+        for(int i=0;i<numOfLights;++i){
+
+            vec3 L = normalize(lights[i].position - fragPosition);  // calc light vector
+            vec3 H = normalize(V + L);                              // calc halfway bisecting vector
+            float dist = length(lights[i].position - fragPosition); // calc distance to light
+            float attenuation = 1.0 / (dist * dist * 0.23);                // calc attenuation
+            vec3 radiance = lights[i].color.rgb * lights[i].intensity * attenuation;         // calc input radiance,light energy comming in
+
+            //Cook-Torrance BRDF distribution function
+            float nDotV = max(dot(N,V),0.0000001);
+            float nDotL = max(dot(N,L),0.0000001);
+            float hDotV = max(dot(H,V),0.0);
+            float nDotH = max(dot(N,H),0.0);
+            float D = ggxDistribution(nDotH,roughness); // larger the more micro-facets aligned to H
+            float G = geomSmith(nDotV,nDotL,roughness); // smaller the more micro-facets shadow
+            vec3 F = schlickFresnel(hDotV, baseRefl);  // fresnel proportion of specular reflectance
+
+            vec3 spec = (D * G * F) / (4.0 * nDotV * nDotL);
+            // difuse and spec light can't be above 1.0
+            // kD = 1.0 - kS  diffuse component is equal 1.0 - spec comonent
+            vec3 kD = vec3(1.0) - F;
+            //mult kD by the inverse of metallnes , only non-metals should have diffuse light
+            kD *= 1.0 - metallic;
+            Lo += ((kD * albedo.rgb / PI + spec) * radiance * nDotL)*float(lights[i].enabled); // angle of light has impact on result
+        }
+        vec3 ambient_final = (ambientColor + albedo)* ambient * 0.5;
+        return ambient_final+Lo*ao+e;
+}
+
+void main()
+{
+       vec3 color = pbr();
+
+        //HDR tonemapping
+        color = pow(color,color + vec3(1.0));
+        //gamma correction
+        color = pow(color,vec3(1.0/2.2));
+
+        gl_FragColor = vec4(color,1.0);
+
+}