feat: displace sphere with live waveform

Upload the per-channel waveform as a texture and displace icosphere
vertices radially in the vertex shader: CH1 drives the northern
hemisphere, CH2 the southern.

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

@@ -1,6 +1,10 @@
 #version 150
 
 uniform mat4 modelViewProjectionMatrix;
+uniform sampler2D waveformTex;   // width = samples, height = 2 (row0 CH1, row1 CH2)
+uniform float displaceAmount;
+uniform float baseRadius;
+
 in vec4 position;
 
 out vec2 vSphereUV;   // x = longitude [0,1], y = latitude [0,1]
@@ -11,6 +15,11 @@ void main() {
     vec3 dir = normalize(position.xyz);
     float lon = atan(dir.z, dir.x) / (2.0 * PI) + 0.5;
     float lat = asin(clamp(dir.y, -1.0, 1.0)) / PI + 0.5;
-    gl_Position = modelViewProjectionMatrix * position;
+
+    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);
+
+    gl_Position = modelViewProjectionMatrix * vec4(dir * r, 1.0);
     vSphereUV = vec2(lon, lat);
 }

oscope-sphere/src/SphereViz.cpp

@@ -1,7 +1,9 @@
 #include "SphereViz.h"
 #include <algorithm>
 
-void SphereViz::setup(int icoIterations, int spectroWidth, int spectroHeight) {
+void SphereViz::setup(int icoIterations, int spectroWidth, int spectroHeight,
+                      int waveformLen) {
+    waveformLen_ = waveformLen;
     spectro_ = std::make_unique<oscope::SpectrogramBuffer>(spectroWidth,
                                                            spectroHeight);
 
@@ -23,6 +25,12 @@ void SphereViz::setup(int icoIterations, int spectroWidth, int spectroHeight) {
     spectroTex_.setTextureWrap(GL_REPEAT, GL_CLAMP_TO_EDGE);
     spectroTex_.setTextureMinMagFilter(GL_LINEAR, GL_LINEAR);
 
+    wavePix_.allocate(waveformLen, 2, OF_PIXELS_GRAY);
+    wavePix_.set(0.0f);
+    waveTex_.allocate(wavePix_);
+    waveTex_.setTextureWrap(GL_REPEAT, GL_CLAMP_TO_EDGE);
+    waveTex_.setTextureMinMagFilter(GL_LINEAR, GL_LINEAR);
+
     if (!shader_.load("shaders/sphere"))
         ofLogError("SphereViz") << "failed to load shaders/sphere";
 }
@@ -37,10 +45,34 @@ void SphereViz::pushSpectrogramColumn(const std::vector<float>& magCh1,
                     static_cast<float>(spectro_->width());
 }
 
+void SphereViz::setWaveform(const std::vector<float>& ch1,
+                            const std::vector<float>& ch2) {
+    float* px = wavePix_.getData();
+    const int L = waveformLen_;
+    auto fillRow = [&](const std::vector<float>& src, int row) {
+        const int n = static_cast<int>(src.size());
+        for (int i = 0; i < L; ++i) {
+            float v = 0.0f;
+            if (n > 0) {
+                int idx = n - L + i;          // newest L samples
+                if (idx < 0) idx = 0;
+                v = src[idx];
+            }
+            px[row * L + i] = v;
+        }
+    };
+    fillRow(ch1, 0);
+    fillRow(ch2, 1);
+    waveTex_.loadData(wavePix_);
+}
+
 void SphereViz::drawSkin() {
     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_);
     mesh_.draw();
     shader_.end();

oscope-sphere/src/SphereViz.h

@@ -4,26 +4,33 @@
 #include <memory>
 #include <vector>
 
-// GL visual unit: an icosphere whose skin is the scrolling spectrogram.
-// The northern hemisphere shows CH1, the southern shows CH2.
+// GL visual unit: an icosphere skinned by the scrolling spectrogram and
+// displaced radially by the live waveform. Northern hemisphere = CH1,
+// southern = CH2.
 class SphereViz {
 public:
-    void setup(int icoIterations, int spectroWidth, int spectroHeight);
+    void setup(int icoIterations, int spectroWidth, int spectroHeight,
+               int waveformLen);
 
-    // Advances the spectrogram by one column and uploads it.
     void pushSpectrogramColumn(const std::vector<float>& magCh1,
                                const std::vector<float>& magCh2);
+    void setWaveform(const std::vector<float>& ch1,
+                     const std::vector<float>& ch2);
 
     void drawSkin();
     void setColormap(int id) { colormapId_ = id; }
 
 private:
     std::unique_ptr<oscope::SpectrogramBuffer> spectro_;
-    ofVboMesh   mesh_;
-    ofShader    shader_;
-    ofTexture   spectroTex_;
+    ofVboMesh     mesh_;
+    ofShader      shader_;
+    ofTexture     spectroTex_;
+    ofTexture     waveTex_;
     ofFloatPixels spectroPix_;
+    ofFloatPixels wavePix_;
+    int   waveformLen_ = 0;
     float baseRadius_  = 200.0f;
     float scrollOffset_ = 0.0f;
+    float displace_    = 0.18f;
     int   colormapId_  = 0;
 };

oscope-sphere/src/ofApp.cpp

@@ -11,7 +11,7 @@ void ofApp::setup() {
     cam_.setNearClip(1.0f);
     cam_.setFarClip(5000.0f);
 
-    sphere_.setup(5, 512, 256);
+    sphere_.setup(5, 512, 256, 1024);
 
     hantek_.setSampleRate(16000000u);
     const oscope::HantekStatus st = hantek_.start();
@@ -46,6 +46,7 @@ void ofApp::update() {
     sphere_.setColormap(colormap_);
     sphere_.pushSpectrogramColumn(analyzerCh1_.magDown(),
                                   analyzerCh2_.magDown());
+    sphere_.setWaveform(buf1_, buf2_);
 }
 
 void ofApp::draw() {