Fix issues with example 18-ibl's shaders.

Change vs_ibl_skybox.sc to correctly use radians instead of degrees when
specifying field-of-view. Additionally, use u_viewRect to find the correct
aspect ratio of the viewport, instead of hard-coding to 4/3.

Change fs_ibl_skybox.sc, fixing a number of small issues and mistakes. These
mistakes would lead to incorrect lighting results, especially with metallic
materials at glancing angles.

This commit does not include the rebuilt .bin output of shaderc for these
shaders.

examples/18-ibl/fs_ibl_mesh.sc

@@ -11,9 +11,9 @@ $input v_view, v_normal
 SAMPLERCUBE(s_texCube, 0);
 SAMPLERCUBE(s_texCubeIrr, 1);
 
-vec3 calcFresnel(vec3 _cspec, float _dot)
+vec3 calcFresnel(vec3 _cspec, float _dot, float _strength)
 {
-	return _cspec + (1.0 - _cspec)*pow(1.0 - _dot, 5.0);
+	return _cspec + (1.0 - _cspec)*pow(1.0 - _dot, 5.0) * _strength;
 }
 
 vec3 calcLambert(vec3 _cdiff, float _ndotl)
@@ -50,35 +50,28 @@ void main()
 	float hdotv = clamp(dot(hh, vv), 0.0, 1.0);
 
 	// Material params.
-	vec3  albedo       = u_rgbDiff.xyz;
-	float reflectivity = u_reflectivity;
-	float gloss        = u_glossiness;
+	vec3  inAlbedo       = u_rgbDiff.xyz;
+	float inReflectivity = u_reflectivity;
+	float inGloss        = u_glossiness;
 
 	// Reflection.
 	vec3 refl;
 	if (0.0 == u_metalOrSpec) // Metalness workflow.
 	{
-		refl = mix(vec3_splat(0.04), albedo, reflectivity);
+		refl = mix(vec3_splat(0.04), inAlbedo, inReflectivity);
 	}
 	else // Specular workflow.
 	{
-		refl = u_rgbSpec.xyz * vec3_splat(reflectivity);
+		refl = u_rgbSpec.xyz * vec3_splat(inReflectivity);
 	}
-	vec3 dirF0 = calcFresnel(refl, hdotv);
-	vec3 envF0 = calcFresnel(refl, ndotv);
+	vec3 albedo = inAlbedo * (1.0 - inReflectivity);
+	vec3 dirFresnel = calcFresnel(refl, hdotv, inGloss);
+	vec3 envFresnel = calcFresnel(refl, ndotv, inGloss);
 
-	// Direct lighting.
-	vec3 dirSpec = dirF0;
-	vec3 dirDiff = albedo * 1.0-dirF0;
-
-	vec3 lambert = u_doDiffuse  * calcLambert(dirDiff, ndotl);
-	vec3 blinn   = u_doSpecular * calcBlinn(dirSpec, ndoth, ndotl, specPwr(gloss));
+	vec3 lambert = u_doDiffuse  * calcLambert(albedo * (1.0 - dirFresnel), ndotl);
+	vec3 blinn   = u_doSpecular * calcBlinn(dirFresnel, ndoth, ndotl, specPwr(inGloss));
 	vec3 direct  = (lambert + blinn)*clight;
 
-	// Indirect lighting.
-	vec3 envSpec = envF0;
-	vec3 envDiff = albedo * 1.0-envF0;
-
 	// Note: Environment textures are filtered with cmft: https://github.com/dariomanesku/cmft
 	// Params used:
 	// --excludeBase true //!< First level mip is not filtered.
@@ -86,7 +79,7 @@ void main()
 	// --glossScale 10    //!< Spec power scale. See: specPwr().
 	// --glossBias 2      //!< Spec power bias. See: specPwr().
 	// --edgeFixup warp   //!< This must be used on DirectX9. When fileted with 'warp', fixCubeLookup() should be used.
-	float mip = 1.0 + 5.0*(1.0 - gloss); // Use mip levels [1..6] for radiance.
+	float mip = 1.0 + 5.0*(1.0 - inGloss); // Use mip levels [1..6] for radiance.
 
 	mat4 mtx;
 	mtx[0] = u_mtx0;
@@ -98,9 +91,11 @@ void main()
 	vec3 cubeN = normalize(instMul(mtx, vec4(nn, 0.0)).xyz);
 	cubeR = fixCubeLookup(cubeR, mip, 256.0);
 
-	vec3 radiance   = u_doSpecularIbl * envSpec * toLinear(textureCubeLod(s_texCube, cubeR, mip).xyz);
-	vec3 irradiance = u_doDiffuseIbl  * envDiff * toLinear(textureCube(s_texCubeIrr, cubeN).xyz);
-	vec3 indirect = radiance + irradiance;
+	vec3 radiance    = toLinear(textureCubeLod(s_texCube, cubeR, mip).xyz);
+	vec3 irradiance  = toLinear(textureCube(s_texCubeIrr, cubeN).xyz);
+	vec3 envDiffuse  = albedo     * irradiance * u_doDiffuseIbl;
+	vec3 envSpecular = envFresnel * radiance   * u_doSpecularIbl;
+	vec3 indirect    = envDiffuse + envSpecular;
 
 	// Color.
 	vec3 color = direct + indirect;

examples/18-ibl/vs_ibl_skybox.sc

@@ -15,9 +15,9 @@ void main()
 {
 	gl_Position = mul(u_modelViewProj, vec4(a_position, 1.0) );
 
-	float fov = 45.0;
+	float fov = radians(45.0);
 	float height = tan(fov*0.5);
-	float aspect = height*(4.0/3.0);
+	float aspect = height*(u_viewRect.z / u_viewRect.w);
 	vec2 tex = (2.0*a_texcoord0-1.0) * vec2(aspect, height);
 
 	mat4 mtx;