Generate random value for SSAO sampling

It should improve SSAO at least with grass.
However this make the algorithm even more sensitive to bad normals.

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@14758 178a84e3-b1eb-0310-8ba1-8eac791a3b58

data/shaders/ssao.frag

@@ -4,7 +4,7 @@ uniform mat4 invprojm;
 uniform mat4 projm;
 uniform vec4 samplePoints[16];
 
-const float strengh = 4.;
+const float strengh = 20.;
 const float radius = .1f;
 
 #define SAMPLES 16
@@ -47,7 +47,9 @@ void main(void)
 		occluderPos /= occluderPos.w;
 
 		float depthDifference = sampleProj.z - (2. * occluderFragmentDepth - 1.0);
-		bl += (distance(occluderPos, FragPos) < radius) ? step(0., depthDifference) : 0.0;
+		// depthDifference between 0 and radius
+		float increment = step(0., depthDifference) * step(-radius, -depthDifference);
+		bl += increment * smoothstep(radius, 0, distance(samplePos, FragPos));
 	}
 
 	// output the result

src/graphics/callbacks.cpp

@@ -494,25 +494,6 @@ void MLAANeigh3Provider::OnSetConstants(IMaterialRendererServices *srv, int)
 
 void SSAOProvider::OnSetConstants(IMaterialRendererServices *srv, int)
 {
-    static const float array[64] = {
-        0.43589, -0.9, 0.667945, 0.,
-        -0.9, 0.43589, 0.667945, 0.,
-        -0.8, -0.6, 0.7, 0.,
-        0.6, 0.8, 0.7, 0.,
-        0.866025, -0.5, 0.6830125, 0.,
-        -0.5, 0.866025, 0.6830125, 0.,
-        -0.3, -0.953939, 0.6269695, 0.,
-        0.953939, 0.3, 0.6269695, 0.,
-        0.3, -0.781025, 0.5405125, 0.,
-        -0.781025, 0.3, 0.5405125, 0.,
-        -0.56, -0.621611, 0.5908055, 0.,
-        0.621611, 0.56, 0.5908055, 0.,
-        0.734847, -0.4, 0.5674235, 0.,
-        -0.4, 0.734847, 0.5674235, 0.,
-        -0.2, -0.6, 0.4, 0.,
-        0.6, 0.2, 0.4, 0.,
-    };
-
     srv->setPixelShaderConstant("invprojm", invprojm.pointer(), 16);
     srv->setPixelShaderConstant("projm", projm.pointer(), 16);
     srv->setPixelShaderConstant("samplePoints[0]", array, 64);

src/graphics/callbacks.hpp

@@ -541,7 +541,19 @@ class SSAOProvider: public CallBase
 {
 private:
     core::matrix4 projm, invprojm;
+    float array[64];
 public:
+    SSAOProvider() : CallBase() {
+      for (unsigned i = 0; i < 64; i++) {
+        array[i] = rand();
+        array[i] /= RAND_MAX;
+        if (i % 4 != 2)
+          array[i] = 2 * array[i] - 1;
+        if (i % 4 == 3)
+          continue;
+      }
+    }
+
     virtual void OnSetConstants(video::IMaterialRendererServices *srv, int);
     void updateIPVMatrix()
     {