fix: render point cloud as real GL points

drawVertices on the indexed skin mesh gave a degenerate gl_PointCoord,
so the round-point discard killed every fragment. Use a dedicated
OF_PRIMITIVE_POINTS mesh, float it 5% outside the skin, enlarge points.

oscope-sphere/bin/data/shaders/sphere.vert

@@ -20,10 +20,11 @@ void main() {
     float row  = (dir.y >= 0.0) ? 0.25 : 0.75;          // CH1 north, CH2 south
     float wave = texture(waveformTex, vec2(lon, row)).r; // [-1,1]
     float r    = baseRadius * (1.0 + displaceAmount * wave);
+    if (renderMode == 1) {
+        r *= 1.05;            // float the point cloud just outside the skin
+        gl_PointSize = 6.0;
+    }
 
     gl_Position = modelViewProjectionMatrix * vec4(dir * r, 1.0);
-    if (renderMode == 1) {
-        gl_PointSize = 3.0;
-    }
     vSphereUV = vec2(lon, lat);
 }

oscope-sphere/src/SphereViz.cpp

@@ -14,6 +14,13 @@ void SphereViz::setup(int icoIterations, int spectroWidth, int spectroHeight,
     mesh_.addNormals(src.getNormals());
     mesh_.addIndices(src.getIndices());
 
+    // A separate GL_POINTS-primitive mesh for layer C. drawVertices() on the
+    // indexed skin mesh does not yield a proper point primitive (gl_PointCoord
+    // ends up degenerate), so the point cloud needs its own points mesh.
+    pointsMesh_.clear();
+    pointsMesh_.setMode(OF_PRIMITIVE_POINTS);
+    pointsMesh_.addVertices(src.getVertices());
+
     // ofDisableArbTex() is a global, app-wide GL state change: it makes all
     // textures use normalized [0,1] coordinates. oscope-sphere has a single
     // SphereViz so this is safe; revisit if other ARB-texture components are
@@ -87,6 +94,6 @@ void SphereViz::drawPoints() {
     shader_.begin();
     bindUniforms();
     shader_.setUniform1i("renderMode", 1);
-    mesh_.drawVertices();
+    pointsMesh_.draw();
     shader_.end();
 }

oscope-sphere/src/SphereViz.h

@@ -26,6 +26,7 @@ private:
 
     std::unique_ptr<oscope::SpectrogramBuffer> spectro_;
     ofVboMesh     mesh_;
+    ofVboMesh     pointsMesh_;
     ofShader      shader_;
     ofTexture     spectroTex_;
     ofTexture     waveTex_;