ADD: CSM with base shadow map

shaders/deferred_lighting.frag

@@ -8,7 +8,8 @@ layout(location=0) out vec4 outColor;
 layout(set=1, binding=0) uniform sampler2D posTex;
 layout(set=1, binding=1) uniform sampler2D normalTex;
 layout(set=1, binding=2) uniform sampler2D albedoTex;
-layout(set=2, binding=0) uniform sampler2D shadowTex;
+// Mixed near + CSM: shadowTex[0] is the near/simple map, 1..N-1 are cascades
+layout(set=2, binding=0) uniform sampler2D shadowTex[4];
 
 const float PI = 3.14159265359;
 
@@ -29,14 +30,29 @@ const vec2 POISSON_16[16] = vec2[16](
     vec2(0.1197, 0.0779), vec2(-0.0905, -0.1203)
 );
 
+uint selectCascadeIndex(vec3 worldPos)
+{
+    // Compute view-space positive depth
+    vec4 vpos = sceneData.view * vec4(worldPos, 1.0);
+    float depthVS = -vpos.z;
+    // Near/simple map covers [0, sceneData.cascadeSplitsView.x)
+    if (depthVS < sceneData.cascadeSplitsView.x) return 0u;
+    if (depthVS < sceneData.cascadeSplitsView.y) return 1u;
+    if (depthVS < sceneData.cascadeSplitsView.z) return 2u;
+    return 3u; // last cascade extends to w
+}
+
 float calcShadowVisibility(vec3 worldPos, vec3 N, vec3 L)
 {
-    vec4 lclip = sceneData.lightViewProj * vec4(worldPos, 1.0);
+    uint ci = selectCascadeIndex(worldPos);
+    mat4 lightMat = sceneData.lightViewProjCascades[ci];
+
+    vec4 lclip = lightMat * vec4(worldPos, 1.0);
     vec3 ndc  = lclip.xyz / lclip.w;
     vec2 suv  = ndc.xy * 0.5 + 0.5;
 
     if (any(lessThan(suv, vec2(0.0))) || any(greaterThan(suv, vec2(1.0))))
-    return 1.0;
+        return 1.0;
 
     float current = clamp(ndc.z, 0.0, 1.0);
 
@@ -48,19 +64,20 @@ float calcShadowVisibility(vec3 worldPos, vec3 N, vec3 L)
     float ddz  = max(abs(dzdx), abs(dzdy));
     float bias = slopeBias + ddz * 0.75;
 
-    ivec2 dim       = textureSize(shadowTex, 0);
+    ivec2 dim       = textureSize(shadowTex[ci], 0);
     vec2  texelSize = 1.0 / vec2(dim);
 
     float baseRadius = 1.25;
-    float radius     = mix(baseRadius, baseRadius * 4.0, current);
+    // Slightly increase filter for farther cascades
+    float radius     = mix(baseRadius, baseRadius * 3.0, float(ci) / 3.0);
 
     float ang = hash12(suv * 4096.0) * 6.2831853;
     vec2  r   = vec2(cos(ang), sin(ang));
     mat2  rot = mat2(r.x, -r.y, r.y, r.x);
 
     const int TAP_COUNT = 16;
-    float occluded = 0.0;
-    float wsum     = 0.0;
+    float visible = 0.0;
+    float wsum    = 0.0;
 
     for (int i = 0; i < TAP_COUNT; ++i)
     {
@@ -70,16 +87,16 @@ float calcShadowVisibility(vec3 worldPos, vec3 N, vec3 L)
         float pr   = length(pu);
         float w    = 1.0 - smoothstep(0.0, 0.65, pr);
 
-        float mapD = texture(shadowTex, suv + off).r;
+        float mapD = texture(shadowTex[ci], suv + off).r;
+        // Reversed-Z friendly compare: visible when current <= map depth
+        float vis  = step(mapD, current + bias);
 
-        float occ  = step(current + bias, mapD);
-
-        occluded += occ * w;
-        wsum     += w;
+        visible += vis * w;
+        wsum    += w;
     }
 
-    float shadow = (wsum > 0.0) ? (occluded / wsum) : 0.0;
-    return 1.0 - shadow;
+    float visibility = (wsum > 0.0) ? (visible / wsum) : 1.0;
+    return visibility;
 }
 
 vec3 fresnelSchlick(float cosTheta, vec3 F0)