Reduced number of cells visited

samples/distancefield/DistanceFieldApp.cc

@@ -101,6 +101,7 @@ void DistanceFieldApp::init()
     mGpuTimer = TimerQuery::create();
 
     // bunny
+    if (!false)
     {
         std::ifstream file(util::pathOf(__FILE__) + "/../../data/bunny.obj");
 
@@ -138,8 +139,10 @@ void DistanceFieldApp::init()
         }
     }
 
+    // mPoints.push_back(glm::vec4(Size / 2));
+
     // data
-    if (false)
+    if (!!false)
     {
         // mPoints.push_back(glm::vec4(Size / 2.0f));
         for (auto i = 0; i < 1000; ++i) // DEBUG
@@ -271,13 +274,14 @@ void DistanceFieldApp::recompute()
         fb.begin(GL_POINTS);
         vao.draw();
         fb.end();
+        glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
+
         mFeedbackQuery->end();
         mGpuTimer->end();
         auto time = TimerQuery::toSeconds(mGpuTimer->getResult64());
         auto pts = mFeedbackQuery->getResult64();
         glow::info() << "Seeds: " << pts << " (" << time * 1000 << " ms, " << (time / pts * 1000 * 1000 * 1000) << " ns/pt)";
     }
-    glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
 
     // march
     {
@@ -305,8 +309,8 @@ void DistanceFieldApp::recompute()
                 fb.begin(GL_POINTS);
                 (outputA ? mVAOQueueB : mVAOQueueA)->bind().drawTransformFeedback(outputA ? mFeedbackB : mFeedbackA);
                 fb.end();
-            }
                 glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
+            }
 
             if (shouldQuery)
             {
@@ -320,8 +324,8 @@ void DistanceFieldApp::recompute()
                 shouldQuery = true;
                 auto pts = mFeedbackQuery->getResult64();
                 auto time = TimerQuery::toSeconds(mGpuTimer->getResult64());
-                glow::info() << "Got " << pts << " indices at iteration " << nextIteration << " (" << time * 1000 << " ms, "
-                             << (time / pts * 1000 * 1000 * 1000) << " ns/pt)";
+                glow::info() << "Got " << pts << " indices at iteration " << nextIteration << " (" << time * 1000
+                             << " ms, " << (time / pts * 1000 * 1000 * 1000) << " ns/pt)";
 
                 forceSync = maxSync;
                 (void)forceSync;
@@ -333,9 +337,12 @@ void DistanceFieldApp::recompute()
             outputA = !outputA;
 
             if (nextIteration > Size * 4)
+            {
+                glow::error() << "Too many iterations, aborting.";
                 break; // DEBUG
             }
         }
+    }
     mGpuTimerEnd->saveTimestamp();
     mGeneratedQuery->end();
     mFragmentsQuery->end();

samples/distancefield/gs-header.glsl

@@ -10,6 +10,18 @@ void notifyNeighbor(int x, int y, int z, int w, int h)
     EmitVertex();
 }
 
+void notifyNeighbor(ivec3 ip, ivec3 is)
+{
+    if (any(lessThan(ip, ivec3(0))) || any(greaterThanEqual(ip, is)))
+        return; // out of bounds
+
+    if (imageAtomicMax(uTexIteration, ip, uNextIteration) == uNextIteration)
+        return; // already emitted
+
+    gPosition = (ip.z * is.y + ip.y) * is.x + ip.x;
+    EmitVertex();
+}
+
 void notifyNeighbors(ivec3 ip)
 {
     ivec3 is = imageSize(uTexNearestPoint);

samples/distancefield/march-shader.gsh

@@ -10,7 +10,17 @@ layout(points, max_vertices = 6) out;
 
 in uint vPosition[1];
 
-ivec3 is = imageSize(uTexNearestPoint);
+const ivec3 is = imageSize(uTexNearestPoint);
+const float maxDistance = is.x + is.y + is.z;
+
+const ivec3 dirs[6] = ivec3[6](
+    ivec3(-1, 0, 0),
+    ivec3(+1, 0, 0),
+    ivec3(0, -1, 0),
+    ivec3(0, +1, 0),
+    ivec3(0, 0, -1),
+    ivec3(0, 0, +1)
+);
 
 void checkNeighbor(ivec3 ip, int dx, int dy, int dz, inout float refDis, inout uint ptIdx)
 {
@@ -40,31 +50,51 @@ void main()
         idx / (is.x * is.y)
     );
 
-    //if (imageLoad(uTexDistanceField, ip).r != dis)
-    //    return; // wrong distance
-
     uint ptIdx = imageLoad(uTexNearestPoint, ip).r;
     uint origIdx = ptIdx;
 
-    float dis = is.x + is.y + is.z;
+    float refDis = maxDistance;
+    vec3 refP = vec3(0);
+
+    // collect candidates
+    float nDistances[6];
 
     // initial dis
     if (origIdx < points.length())
     {
-        vec3 currP = points[ptIdx].xyz;
-        dis = primitiveDistance(ip, currP);
+        refP = points[ptIdx].xyz;
+        refDis = primitiveDistance(ip, refP);
+    }
+
+    // check neighbors
+    for (int i = 0; i < 6; ++i)
+    {
+        ivec3 np = ip + dirs[i];
+        uint nIdx = imageLoad(uTexNearestPoint, np).x;
+
+        // no change possible
+        if (nIdx == INVALID_POINT)
+        {
+            nDistances[i] = maxDistance;
         }
+        else
+        {
+            vec3 nPos = points[nIdx].xyz;
+            float nDis = primitiveDistance(ip, nPos); // distance to ip!
+
+            nDistances[i] = primitiveDistance(np, nPos); // distance to np!
 
-    // check nearest
-    checkNeighbor(ip, +1, 0, 0, dis, ptIdx);
-    checkNeighbor(ip, -1, 0, 0, dis, ptIdx);
-    checkNeighbor(ip, 0, +1, 0, dis, ptIdx);
-    checkNeighbor(ip, 0, -1, 0, dis, ptIdx);
-    checkNeighbor(ip, 0, 0, +1, dis, ptIdx);
-    checkNeighbor(ip, 0, 0, -1, dis, ptIdx);
+            if (nDis < refDis) // update
+            {
+                refDis = nDis;
+                refP = nPos;
+                ptIdx = nIdx;
+            }
+        }
+    }
 
     // crust
-    if (dis > uCrustSize)
+    if (refDis > uCrustSize)
         return;
 
     // notify neighbors if changed
@@ -74,6 +104,14 @@ void main()
         imageStore(uTexNearestPoint, ip, uvec4(ptIdx));
 
         // notify
-        notifyNeighbors(ip);
+        for (int i = 0; i < 6; ++i)
+        {
+            ivec3 np = ip + dirs[i];
+
+            // only if update expected
+            float newDis = primitiveDistance(np, refP);
+            if (newDis < nDistances[i])
+                notifyNeighbor(np, is);
+        }
     }
 }