Change ssao to work on depth only.

data/ssao.glsl

@@ -1,34 +1,40 @@
-out vec4 color;
+#section FRAGMENT_SHADER
+out float color;
 in vec2 uv;
 
-uniform sampler2D position_map;
-uniform sampler2D normal_map;
+uniform sampler2D depth_map;
 uniform sampler2D ssao_noise;
 uniform sampler2D ssao_kernel;
 
 uniform float radius = 8;
 uniform float bias = 5;
 
+vec3 view_position(vec2 coords) {
+  float depth = texture(depth_map, coords).r;
+  vec4 ndc = vec4(coords.x*2-1, coords.y*2-1, depth*2-1, 1);
+
+  vec4 vs_pos = inv_projection_matrix * ndc;
+  vs_pos.xyz = vs_pos.xyz / vs_pos.w;
+  return vs_pos.xyz;
+}
+
 void main(){
-  vec2 noiseScale = view_size / 4.0;
+  vec2 noise_scale = textureSize(depth_map, 0).xy / 4.0;
   // get input for SSAO algorithm
-  vec3 fragPos = texture(position_map, uv).xyz;
-  vec3 normal = texture(normal_map, uv).rgb;
-  vec3 randomVec = normalize(texture(ssao_noise, uv * noiseScale).xyz);
-  // bring into view space
-  fragPos = vec3(view_matrix * vec4(fragPos, 1));
-  normal = normalize(transpose(inverse(mat3(view_matrix))) * normal);
+  vec3 view_position = view_position(position_map, uv);
+  vec3 view_normal = cross(dFdy(view_position.xyz), dFdx(view_position.xyz));
+  vec3 random_vec = normalize(texture(ssao_noise, uv * noise_scale).xyz);
   // create TBN change-of-basis matrix: from tangent-space to view-space
-  vec3 tangent = normalize(randomVec - normal * dot(randomVec, normal));
+  vec3 tangent = normalize(random_vec - view_normal * dot(random_vec, view_normal));
   vec3 bitangent = cross(normal, tangent);
-  mat3 TBN = mat3(tangent, bitangent, normal);
+  mat3 TBN = mat3(tangent, bitangent, view_normal);
   // iterate over the sample kernel and calculate occlusion factor
   float occlusion = 0.0;
   int kernel_size = textureSize(ssao_kernel, 0).x;
   for(int i = 0; i < kernel_size; ++i){
     // get sample position
     vec3 ssample = TBN * texelFetch(ssao_kernel, i).rgb; // from tangent to view-space
-    ssample = fragPos + ssample * radius;
+    ssample = view_position + ssample * radius;
 
     // project sample position (to sample texture) (to get position on screen/texture)
     vec4 offset = vec4(ssample, 1.0);
@@ -37,15 +43,10 @@ void main(){
     offset.xy = offset.xy * 0.5 + 0.5; // transform to range 0.0 - 1.0
 
     // get sample depth
-    vec3 samplePos = texture(position_map, offset.xy).xyz;
-    samplePos = vec3(view_matrix * vec4(samplePos, 1));
-    float sampleDepth = samplePos.z;
-
-    // range check & accumulate
-    float rangeCheck = smoothstep(0.0, 1.0, radius / abs(fragPos.z - sampleDepth));
-    occlusion += (sampleDepth >= ssample.z + bias ? 1.0 : 0.0) * rangeCheck;
+    float sample_depth = view_position(offset.xy).z;
+    float range_check = smoothstep(0.0, 1.0, radius / abs(view_position.z - sample_depth));
+    occlusion += (sample_depth >= ssample.z + bias ? 1.0 : 0.0) * range_check;
   }
   occlusion = 1.0 - (occlusion / kernel_size);
-
-  color = vec4(pow(occlusion, 2));
+  color = pow(occlusion, 2);
 }

renderer/ssao.lisp

@@ -35,14 +35,15 @@
   :internal-format :rgb32f)
 
 (define-shader-pass ssao-pass (post-effect-pass)
-  ((position-map :port-type input)
-   (normal-map :port-type input)
+  ((depth-map :port-type input)
    (occlusion :port-type output
               :attachment :color-attachment0
               :texspec (:internal-format :red
                         :min-filter :nearest
                         :mag-filter :nearest))
    (ssao-kernel :port-type fixed-input :texture (// 'trial 'ssao-kernel))
-   (ssao-noise :port-type fixed-input :texture (// 'trial 'ssao-noise)))
+   (ssao-noise :port-type fixed-input :texture (// 'trial 'ssao-noise))
+   (radius :initform 8.0 :accessor radius :uniform T)
+   (bias :initform 5.0 :accessor radius :uniform T))
   (:buffers (trial standard-environment-information))
   (:shader-file (trial "ssao.glsl")))