Adapt standard shader to GL ES 2.0

Some shader calculations are now pre-calculated because some math
functions doesn't exist in glsl 110.

src/rlgl.c

@@ -1795,8 +1795,13 @@ void rlglDrawMesh(Mesh mesh, Material material, Matrix transform)
     // NOTE: standard shader specific locations are got at render time to keep Shader struct as simple as possible (with just default shader locations)
     if (material.shader.id == standardShader.id)
     {
+        // Transpose and inverse model transformations matrix for fragment normal calculations
+        Matrix transInvTransform = transform;
+        MatrixTranspose(&transInvTransform);
+        MatrixInvert(&transInvTransform);
+        
         // Send model transformations matrix to shader
-        glUniformMatrix4fv(glGetUniformLocation(material.shader.id, "modelMatrix"), 1, false, MatrixToFloat(transform));
+        glUniformMatrix4fv(glGetUniformLocation(material.shader.id, "modelMatrix"), 1, false, MatrixToFloat(transInvTransform));
         
         // Send view transformation matrix to shader. View matrix 8, 9 and 10 are view direction vector axis values (target - position)
         glUniform3f(glGetUniformLocation(material.shader.id, "viewDir"), matView.m8, matView.m9, matView.m10);

src/standard_shader.h

@@ -85,13 +85,13 @@ static const char fStandardShaderStr[] =
 "{\n"
 "    vec3 surfacePos = vec3(modelMatrix*vec4(fragPosition, 1));\n"
 "    vec3 surfaceToLight = l.position - surfacePos;\n"
-"    float brightness = clamp(dot(n, surfaceToLight)/(length(surfaceToLight)*length(n)), 0, 1);\n"
+"    float brightness = clamp(float(dot(n, surfaceToLight)/(length(surfaceToLight)*length(n))), 0.0, 1.0);\n"
 "    float diff = 1.0/dot(surfaceToLight/l.radius, surfaceToLight/l.radius)*brightness*l.intensity;\n"
 "    float spec = 0.0;\n"
 "    if (diff > 0.0)\n"
 "    {\n"
 "        vec3 h = normalize(-l.direction + v);\n"
-"        spec = pow(dot(n, h), 3 + glossiness)*s;\n"
+"        spec = pow(dot(n, h), 3.0 + glossiness)*s;\n"
 "    }\n"
 "    return (diff*l.diffuse.rgb + spec*colSpecular.rgb);\n"
 "}\n"
@@ -99,23 +99,23 @@ static const char fStandardShaderStr[] =
 "vec3 CalcDirectionalLight(Light l, vec3 n, vec3 v, float s)\n"
 "{\n"
 "    vec3 lightDir = normalize(-l.direction);\n"
-"    float diff = clamp(dot(n, lightDir), 0.0, 1.0)*l.intensity;\n"
+"    float diff = clamp(float(dot(n, lightDir)), 0.0, 1.0)*l.intensity;\n"
 "    float spec = 0.0;\n"
 "    if (diff > 0.0)\n"
 "    {\n"
 "        vec3 h = normalize(lightDir + v);\n"
-"        spec = pow(dot(n, h), 3 + glossiness)*s;\n"
+"        spec = pow(dot(n, h), 3.0 + glossiness)*s;\n"
 "    }\n"
 "    return (diff*l.intensity*l.diffuse.rgb + spec*colSpecular.rgb);\n"
 "}\n"
 "\n"
 "vec3 CalcSpotLight(Light l, vec3 n, vec3 v, float s)\n"
 "{\n"
-"    vec3 surfacePos = vec3(modelMatrix*vec4(fragPosition, 1));\n"
+"    vec3 surfacePos = vec3(modelMatrix*vec4(fragPosition, 1.0));\n"
 "    vec3 lightToSurface = normalize(surfacePos - l.position);\n"
 "    vec3 lightDir = normalize(-l.direction);\n"
-"    float diff = clamp(dot(n, lightDir), 0.0, 1.0)*l.intensity;\n"
-"    float attenuation = clamp(dot(n, lightToSurface), 0.0, 1.0);\n"
+"    float diff = clamp(float(dot(n, lightDir)), 0.0, 1.0)*l.intensity;\n"
+"    float attenuation = clamp(float(dot(n, lightToSurface)), 0.0, 1.0);\n"
 "    attenuation = dot(lightToSurface, -lightDir);\n"
 "    float lightToSurfaceAngle = degrees(acos(attenuation));\n"
 "    if (lightToSurfaceAngle > l.coneAngle) attenuation = 0.0;\n"
@@ -125,37 +125,45 @@ static const char fStandardShaderStr[] =
 "    if (diffAttenuation > 0.0)\n"
 "    {\n"
 "        vec3 h = normalize(lightDir + v);\n"
-"        spec = pow(dot(n, h), 3 + glossiness)*s;\n"
+"        spec = pow(dot(n, h), 3.0 + glossiness)*s;\n"
 "    }\n"
 "    return (falloff*(diffAttenuation*l.diffuse.rgb + spec*colSpecular.rgb));\n"
 "}\n"
 "\n"
 "void main()\n"
 "{\n"
-"    mat3 normalMatrix = transpose(inverse(mat3(modelMatrix)));\n"
+"    mat3 normalMatrix = mat3(modelMatrix);\n"
 "    vec3 normal = normalize(normalMatrix*fragNormal);\n"
 "    vec3 n = normalize(normal);\n"
 "    vec3 v = normalize(viewDir);\n"
+#if defined(GRAPHICS_API_OPENGL_ES2) || defined(GRAPHICS_API_OPENGL_21)
+"    vec4 texelColor = texture2D(texture0, fragTexCoord);\n"
+#elif defined(GRAPHICS_API_OPENGL_33)
 "    vec4 texelColor = texture(texture0, fragTexCoord);\n"
+#endif
 "    vec3 lighting = colAmbient.rgb;\n"
 "    if (useNormal == 1)\n"
 "    {\n"
+#if defined(GRAPHICS_API_OPENGL_ES2) || defined(GRAPHICS_API_OPENGL_21)
+"        n *= texture2D(texture1, fragTexCoord).rgb;\n"
+#elif defined(GRAPHICS_API_OPENGL_33)
 "        n *= texture(texture1, fragTexCoord).rgb;\n"
+#endif
 "        n = normalize(n);\n"
 "    }\n"
 "    float spec = 1.0;\n"
+#if defined(GRAPHICS_API_OPENGL_ES2) || defined(GRAPHICS_API_OPENGL_21)
+"    if (useSpecular == 1) spec *= normalize(texture2D(texture2, fragTexCoord).r);\n"
+#elif defined(GRAPHICS_API_OPENGL_33)
 "    if (useSpecular == 1) spec *= normalize(texture(texture2, fragTexCoord).r);\n"
+#endif
 "    for (int i = 0; i < lightsCount; i++)\n"
 "    {\n"
 "        if (lights[i].enabled == 1)\n"
 "        {\n"
-"            switch (lights[i].type)\n"
-"            {\n"
-"                case 0: lighting += CalcPointLight(lights[i], n, v, spec); break;\n"
-"                case 1: lighting += CalcDirectionalLight(lights[i], n, v, spec); break;\n"
-"                case 2: lighting += CalcSpotLight(lights[i], n, v, spec); break;\n"
-"                default: break;\n"
-"            }\n"
+"            if(lights[i].type == 0) lighting += CalcPointLight(lights[i], n, v, spec);\n"
+"            else if(lights[i].type == 1) lighting += CalcDirectionalLight(lights[i], n, v, spec);\n"
+"            else if(lights[i].type == 2) lighting += CalcSpotLight(lights[i], n, v, spec);\n"
 "        }\n"
 "    }\n"
 #if defined(GRAPHICS_API_OPENGL_33)