[Refraction] Greatly improved (physically based and does chromatic ab…

…erration as well)
PanosK92 · Oct 24, 2023 · c812d4e · c812d4e
1 parent bc466a8
commit c812d4e
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Showing 2 changed files with 52 additions and 12 deletions.
diff --git a/data/shaders/light_composition.hlsl b/data/shaders/light_composition.hlsl
@@ -23,18 +23,58 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include "common.hlsl"
 //====================
 
+float compute_fade_factor(float2 uv)
+{
+    float edge_threshold = 0.05f; // how close to the edge to start fading
+    float2 edge_distance = min(uv, 1.0f - uv);
+    return saturate(min(edge_distance.x, edge_distance.y) / edge_threshold);
+}
+
+float3 refract_vector(float3 i, float3 n, float eta)
+{
+    float cosi = dot(-i, n);
+    float cost2 = 1.0f - eta * eta * (1.0f - cosi * cosi);
+    return eta * i + (eta * cosi - sqrt(abs(cost2))) * n;
+}
+
 float3 refraction(Surface surface, float ior, float scale, float depth_bias)
 {
-    float distance_falloff        = clamp(1.0f / world_to_view(surface.position).z, -3.0f, 3.0f);
-    float2 refraction_normal      = world_to_view(surface.normal.xyz, false).xy ;
-    float2 refraction_uv_offset   = refraction_normal * distance_falloff * scale * max(0.0f, ior - 1.0f);
-    float depth_surface           = get_linear_depth(surface.depth);
-    float depth_surface_refracted = get_linear_depth(surface.uv + refraction_uv_offset);
-    float is_behind               = step(depth_surface - depth_bias, depth_surface_refracted);
-    float frame_mip_count         = pass_get_f3_value().x;
-    float mip_level               = lerp(0, frame_mip_count, surface.roughness_alpha);
-
-    return tex_frame.SampleLevel(samplers[sampler_trilinear_clamp], surface.uv + refraction_uv_offset * is_behind, mip_level).rgb;
+    const float chromatic_aberration_strength = 0.0012f;
+
+    float3 view_pos    = world_to_view(surface.position);
+    float3 view_normal = world_to_view(surface.normal, false);
+    float3 view_dir    = normalize(view_pos);
+
+    // compute refracted uv
+    float3 refracted_dir        = refract_vector(view_dir, view_normal, 1.0f / ior);
+    float2 refraction_uv_offset = refracted_dir.xy * scale;
+    float2 refracted_uv         = surface.uv + refraction_uv_offset;
+
+    // get mip level
+    float frame_mip_count = pass_get_f3_value().x;
+    float mip_level       = lerp(0, frame_mip_count, surface.roughness_alpha);
+
+    // chromatic aberration
+    float3 color_refracted = float3(0, 0, 0);
+    {
+        float2 ca_offsets[3];
+        ca_offsets[0] = float2(chromatic_aberration_strength, 0.0f);
+        ca_offsets[1] = float2(0.0f, 0.0f);
+        ca_offsets[2] = float2(-chromatic_aberration_strength, 0.0f); 
+
+        [unroll]
+        for (int i = 0; i < 3; ++i)
+        {
+            float4 sampled_color = tex_frame.SampleLevel(samplers[sampler_trilinear_clamp], refracted_uv + ca_offsets[i], mip_level);
+            color_refracted[i] = sampled_color[i];
+        }
+    }
+
+    // screen fade
+    float fade_factor     = compute_fade_factor(refracted_uv);
+    float3 color_original = tex_frame.SampleLevel(samplers[sampler_trilinear_clamp], surface.uv, mip_level).rgb;
+
+    return lerp(color_original, color_refracted, fade_factor);
 }
 
 [numthreads(THREAD_GROUP_COUNT_X, THREAD_GROUP_COUNT_Y, 1)]
@@ -71,7 +111,7 @@ void mainCS(uint3 thread_id : SV_DispatchThreadID)
         if (surface.is_transparent())
         {
             float ior        = 1.33; // water
-            float scale      = 0.1f;
+            float scale      = 0.05f;
             float depth_bias = 0.02f;
             light_refraction = refraction(surface, ior, scale, depth_bias); 
         }

diff --git a/runtime/World/World.cpp b/runtime/World/World.cpp
@@ -869,7 +869,7 @@ namespace Spartan
                     {
                         shared_ptr<Material> material = make_shared<Material>();
                         material->SetObjectName("material_water");
-                        material->SetColor(Color(0.0f, 48.0f / 255.0f, 75.0f / 255.0f, 70.0f / 255.0f));
+                        material->SetColor(Color(0.0f, 48.0f / 255.0f, 75.0f / 255.0f, 50.0f / 255.0f));
                         material->SetTexture(MaterialTexture::Normal,                "project\\terrain\\water_normal_2.jpeg");
                         material->SetProperty(MaterialProperty::AnimateUVs,          1.0f);
                         material->SetProperty(MaterialProperty::RoughnessMultiplier, 0.2f); // just a bit of roughness to diffuse the sun a little