1 files changed, 56 insertions, 9 deletions

diff --git a/shaders/model.frag.slang b/shaders/model.frag.slang
index 4684db0..ac12d0e 100644
--- a/shaders/model.frag.slang
+++ b/shaders/model.frag.slang
@@ -16,10 +16,29 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
+struct light_uniforms {
+    float3 direction;
+    float  shadow_texel_size;
+    float  shadow_minimum_bias;
+    float  shadow_maximum_bias;
+    float  shadow_strength;
+    float  padding;
+};
+
+[[vk::binding(0, 3)]]
+ConstantBuffer<light_uniforms> light : register(b0, space3);
+
+[[vk::binding(0, 2)]]
+Texture2D<float> shadow_map : register(t0, space2);
+
+[[vk::binding(1, 2)]]
+SamplerComparisonState shadow_sampler : register(s0, space2);
+
 struct FSInput {
-    float3 normal          : TEXCOORD0;
-    float3 world_position  : TEXCOORD1;
-    float3 camera_position : TEXCOORD2;
+    float3 normal               : TEXCOORD0;
+    float3 world_position       : TEXCOORD1;
+    float3 camera_position      : TEXCOORD2;
+    float4 light_space_position : TEXCOORD3;
 };
 
 struct FSOutput {
@@ -30,17 +49,45 @@ static const float ambient_strength  = 0.22;
 static const float diffuse_strength  = 0.78;
 static const float specular_strength = 0.6;
 static const float shininess         = 32.0;
+static const int   shadow_pcf_radius = 1;
+
+float shadow_visibility(float4 light_space_position, float normal_dot_light) {
+    float3 projected = light_space_position.xyz / light_space_position.w;
+    if (projected.z < 0.0 || projected.z > 1.0) {
+        return 1.0;
+    }
+
+    float2 uv = float2(0.5 + 0.5 * projected.x, 0.5 - 0.5 * projected.y);
+    if (any(uv < 0.0) || any(uv > 1.0)) {
+        return 1.0;
+    }
+
+    float bias       = max(light.shadow_maximum_bias * (1.0 - normal_dot_light), light.shadow_minimum_bias);
+    float reference  = projected.z - bias;
+    float visibility = 0.0;
+    float taps       = 0.0;
+    for (int y = -shadow_pcf_radius; y <= shadow_pcf_radius; y++) {
+        for (int x = -shadow_pcf_radius; x <= shadow_pcf_radius; x++) {
+            float2 offset = float2(x, y) * light.shadow_texel_size;
+            visibility += shadow_map.SampleCmpLevelZero(shadow_sampler, uv + offset, reference);
+            taps       += 1.0;
+        }
+    }
+
+    return visibility / taps;
+}
 
 FSOutput main(FSInput input) {
-    float3 light_direction   = normalize(float3(-0.45, 0.75, 0.55));
+    float3 light_direction   = normalize(light.direction);
     float3 normal            = normalize(input.normal);
     float3 view_direction    = normalize(input.camera_position - input.world_position);
     float3 halfway_direction = normalize(light_direction + view_direction);
-
-    float diffuse  = max(dot(normal, light_direction), 0.0);
-    float specular = diffuse > 0.0 ? pow(max(dot(normal, halfway_direction), 0.0), shininess) : 0.0;
-
-    float shade = saturate(ambient_strength + diffuse * diffuse_strength + specular * specular_strength);
+    float normal_dot_light   = dot(normal, light_direction);
+    float diffuse            = max(normal_dot_light, 0.0);
+    float specular           = diffuse > 0.0 ? pow(max(dot(normal, halfway_direction), 0.0), shininess) : 0.0;
+    float visibility         = shadow_visibility(input.light_space_position, normal_dot_light);
+    visibility               = lerp(1.0, visibility, light.shadow_strength);
+    float shade              = saturate(ambient_strength + visibility * (diffuse * diffuse_strength + specular * specular_strength));
     FSOutput output;
     output.out_color = float4(shade, shade, shade, 1.0);
     return output;