feat: add point-cloud sphere layer

Render the icosphere vertices as rounded points sharing the skin's
displacement and colormap, switched by a renderMode uniform and
toggled with key 3.

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

@@ -3,6 +3,7 @@
 uniform sampler2D spectroTex;   // width = time, height = freq, R32F [0,1]
 uniform float scrollOffset;
 uniform int   colormapId;
+uniform int   renderMode;       // 0 = skin, 1 = points
 
 in vec2 vSphereUV;
 out vec4 fragColor;
@@ -33,5 +34,9 @@ void main() {
     float u = fract(vSphereUV.x - scrollOffset);
     float mag = clamp(texture(spectroTex, vec2(u, vSphereUV.y)).r, 0.0, 1.0);
     vec3 col = (colormapId == 0) ? magma(mag) : viridis(mag);
+    if (renderMode == 1) {
+        vec2 d = gl_PointCoord - vec2(0.5);
+        if (dot(d, d) > 0.25) discard;       // round the points
+    }
     fragColor = vec4(col, 1.0);
 }

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

@@ -4,6 +4,7 @@ uniform mat4 modelViewProjectionMatrix;
 uniform sampler2D waveformTex;   // width = samples, height = 2 (row0 CH1, row1 CH2)
 uniform float displaceAmount;
 uniform float baseRadius;
+uniform int   renderMode;        // 0 = skin, 1 = points
 
 in vec4 position;
 
@@ -21,5 +22,8 @@ void main() {
     float r    = baseRadius * (1.0 + displaceAmount * wave);
 
     gl_Position = modelViewProjectionMatrix * vec4(dir * r, 1.0);
+    if (renderMode == 1) {
+        gl_PointSize = 3.0;
+    }
     vSphereUV = vec2(lon, lat);
 }

oscope-sphere/src/SphereViz.cpp

@@ -74,6 +74,20 @@ void SphereViz::drawSkin() {
     shader_.setUniform1f("displaceAmount", displace_);
     shader_.setUniform1f("baseRadius", baseRadius_);
     shader_.setUniform1i("colormapId", colormapId_);
+    shader_.setUniform1i("renderMode", 0);
     mesh_.draw();
     shader_.end();
 }
+
+void SphereViz::drawPoints() {
+    shader_.begin();
+    shader_.setUniformTexture("spectroTex", spectroTex_, 0);
+    shader_.setUniformTexture("waveformTex", waveTex_, 1);
+    shader_.setUniform1f("scrollOffset", scrollOffset_);
+    shader_.setUniform1f("displaceAmount", displace_);
+    shader_.setUniform1f("baseRadius", baseRadius_);
+    shader_.setUniform1i("colormapId", colormapId_);
+    shader_.setUniform1i("renderMode", 1);
+    mesh_.drawVertices();
+    shader_.end();
+}

oscope-sphere/src/SphereViz.h

@@ -18,6 +18,7 @@ public:
                      const std::vector<float>& ch2);
 
     void drawSkin();
+    void drawPoints();
     void setColormap(int id) { colormapId_ = id; }
 
 private:

oscope-sphere/src/ofApp.cpp

@@ -56,6 +56,7 @@ void ofApp::draw() {
     ofPushMatrix();
     ofRotateYDeg(ofGetElapsedTimef() * 6.0f);
     if (layerA_) sphere_.drawSkin();
+    if (layerC_) sphere_.drawPoints();
     if (layerB_) rings_.draw();
     ofPopMatrix();
     cam_.end();