Workbench: SeeThrough

added a fresnel effect

TODO: solve memory leak

2 files changed, 36 insertions, 0 deletions

diff --git a/source/blender/draw/engines/workbench/shaders/workbench_common_lib.glsl b/source/blender/draw/engines/workbench/shaders/workbench_common_lib.glsl
index 5b646f8e911..2550f44271b 100644
--- a/source/blender/draw/engines/workbench/shaders/workbench_common_lib.glsl
+++ b/source/blender/draw/engines/workbench/shaders/workbench_common_lib.glsl
@@ -35,3 +35,30 @@ vec2 normal_encode(vec3 n)
 	float p = sqrt(n.z * 8.0 + 8.0);
 	return vec2(n.xy / p + 0.5);
 }
+
+void fresnel(vec3 I, vec3 N, float ior, out float kr)
+{
+	float cosi = clamp(dot(I, N), -1.0, 1.0);
+	float etai = 1.0;
+	float etat = ior;
+	if (cosi > 0) {
+		etat = 1.0;
+		etai = ior;
+	}
+
+	// Compute sini using Snell's law
+	float sint = etai / etat * sqrt(max(0.0, 1.0 - cosi * cosi));
+	// Total internal reflection
+	if (sint >= 1) {
+		kr = 1;
+	}
+	else {
+		float cost = sqrt(max(0.0, 1.0 - sint * sint));
+		cosi = abs(cosi);
+		float Rs = ((etat * cosi) - (etai * cost)) / ((etat * cosi) + (etai * cost));
+		float Rp = ((etai * cosi) - (etat * cost)) / ((etai * cosi) + (etat * cost));
+		kr = (Rs * Rs + Rp * Rp) / 2;
+	}
+	// As a consequence of the conservation of energy, transmittance is given by:
+	// kt = 1 - kr;
+}
diff --git a/source/blender/draw/engines/workbench/shaders/workbench_forward_transparent_accum_frag.glsl b/source/blender/draw/engines/workbench/shaders/workbench_forward_transparent_accum_frag.glsl
index 7eb5336e303..78981522c18 100644
--- a/source/blender/draw/engines/workbench/shaders/workbench_forward_transparent_accum_frag.glsl
+++ b/source/blender/draw/engines/workbench/shaders/workbench_forward_transparent_accum_frag.glsl
@@ -48,7 +48,16 @@ void main()
 #endif /* V3D_LIGHTING_STUDIO */
 
 	float alpha = world_data.see_through_transparency;
+#ifdef NORMAL_VIEWPORT_PASS_ENABLED
+	vec3 normal = normalize(normal_viewport);
+	float kr;
+	fresnel(vec3(0.0, 0.0, -1.0), normal, 1.22, kr);
+	alpha = mix(alpha, alpha+alpha, kr);
+#endif
+
 	vec4 premultiplied = vec4(shaded_color.rgb * alpha, alpha);
+
 	transparentAccum = calculate_transparent_accum(premultiplied);
+
 }