From 6198236db338e73ce55898c9696bec5e1d8cb9cc Mon Sep 17 00:00:00 2001
From: Tanner Collin <git@tannercollin.com>
Date: Mon, 9 Feb 2026 15:57:03 -0700
Subject: [PATCH] feat: Add top-right viewport view cube with axis and face
 labels

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>
---
 src/ViewportWidget.cpp | 127 +++++++++++++++++++++++++++++++++++++++++
 src/ViewportWidget.h   |   2 +
 2 files changed, 129 insertions(+)

diff --git a/src/ViewportWidget.cpp b/src/ViewportWidget.cpp
index 37128a9..4c8ae18 100644
--- a/src/ViewportWidget.cpp
+++ b/src/ViewportWidget.cpp
@@ -2,6 +2,9 @@
 #include <QMouseEvent>
 #include <QWheelEvent>
 #include <QApplication>
+#include <QPainter>
+#include <QFontMetrics>
+#include <QVector3D>
 
 ViewportWidget::ViewportWidget(QWidget *parent)
     : QOpenGLWidget(parent)
@@ -17,6 +20,8 @@ void ViewportWidget::initializeGL()
 
 void ViewportWidget::paintGL()
 {
+    // Main scene rendering
+    glViewport(0, 0, width(), height());
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
     QMatrix4x4 model;
@@ -33,6 +38,63 @@ void ViewportWidget::paintGL()
     glLoadMatrixf(model.constData());
 
     drawCube();
+
+    // View cube rendering in top right
+    int viewCubeSize = 150;
+    glViewport(width() - viewCubeSize, height() - viewCubeSize, viewCubeSize, viewCubeSize);
+    glClear(GL_DEPTH_BUFFER_BIT);
+
+    QMatrix4x4 viewCubeProjection;
+    viewCubeProjection.ortho(-2, 2, -2, 2, -10, 10);
+
+    QMatrix4x4 viewCubeModel;
+    viewCubeModel.rotate(xRot / 16.0f, 1, 0, 0);
+    viewCubeModel.rotate(yRot / 16.0f, 0, 1, 0);
+
+    glMatrixMode(GL_PROJECTION);
+    glLoadMatrixf(viewCubeProjection.constData());
+
+    glMatrixMode(GL_MODELVIEW);
+    glLoadMatrixf(viewCubeModel.constData());
+
+    drawViewCube();
+    drawAxes();
+
+    glViewport(0, 0, width(), height());
+
+    // Text rendering with QPainter
+    QPainter painter(this);
+    painter.setPen(Qt::white);
+    painter.setFont(QFont("Arial", 10));
+
+    struct Face {
+        QString name;
+        QVector3D center;
+        QVector3D normal;
+    };
+    QVector<Face> faces = {
+        {"FRONT", {0, 0, 1.0}, {0, 0, 1}},
+        {"BACK",  {0, 0, -1.0}, {0, 0, -1}},
+        {"TOP",   {0, 1.0, 0}, {0, 1, 0}},
+        {"BOTTOM",{0, -1.0, 0}, {0, -1, 0}},
+        {"RIGHT", {1.0, 0, 0}, {1, 0, 0}},
+        {"LEFT",  {-1.0, 0, 0}, {-1, 0, 0}}
+    };
+
+    for (const auto& face : faces) {
+        QVector3D transformedNormal = viewCubeModel.mapVector(face.normal);
+        // Use a small epsilon for floating point comparison
+        if (transformedNormal.z() > 0.1) { // Simple back-face culling
+            QRect viewportRect(width() - viewCubeSize, 0, viewCubeSize, viewCubeSize);
+            QVector3D pos2D = face.center.project(viewCubeModel, viewCubeProjection, viewportRect);
+
+            QFontMetrics metrics(painter.font());
+            int textWidth = metrics.horizontalAdvance(face.name);
+            int textHeight = metrics.height();
+            QRect textRect(pos2D.x() - textWidth / 2, pos2D.y() - textHeight / 2, textWidth, textHeight);
+            painter.drawText(textRect, Qt::AlignCenter, face.name);
+        }
+    }
 }
 
 void ViewportWidget::resizeGL(int w, int h)
@@ -75,6 +137,71 @@ void ViewportWidget::wheelEvent(QWheelEvent *event)
     update();
 }
 
+void ViewportWidget::drawViewCube()
+{
+    float size = 0.75;
+    glBegin(GL_QUADS);
+    // All faces are light gray
+    glColor3f(0.8, 0.8, 0.8);
+
+    // Front face
+    glVertex3f(-size, -size, size);
+    glVertex3f(size, -size, size);
+    glVertex3f(size, size, size);
+    glVertex3f(-size, size, size);
+
+    // Back face
+    glVertex3f(-size, -size, -size);
+    glVertex3f(-size, size, -size);
+    glVertex3f(size, size, -size);
+    glVertex3f(size, -size, -size);
+
+    // Top face
+    glVertex3f(-size, size, -size);
+    glVertex3f(-size, size, size);
+    glVertex3f(size, size, size);
+    glVertex3f(size, size, -size);
+
+    // Bottom face
+    glVertex3f(-size, -size, -size);
+    glVertex3f(size, -size, -size);
+    glVertex3f(size, -size, size);
+    glVertex3f(-size, -size, size);
+
+    // Right face
+    glVertex3f(size, -size, -size);
+    glVertex3f(size, size, -size);
+    glVertex3f(size, size, size);
+    glVertex3f(size, -size, size);
+
+    // Left face
+    glVertex3f(-size, -size, -size);
+    glVertex3f(-size, -size, size);
+    glVertex3f(-size, size, size);
+    glVertex3f(-size, size, -size);
+    glEnd();
+}
+
+void ViewportWidget::drawAxes()
+{
+    glLineWidth(2.0f);
+    glBegin(GL_LINES);
+    // X-axis (red)
+    glColor3f(1.0, 0.0, 0.0);
+    glVertex3f(0.0, 0.0, 0.0);
+    glVertex3f(1.5, 0.0, 0.0);
+    // Y-axis (green)
+    glColor3f(0.0, 1.0, 0.0);
+    glVertex3f(0.0, 0.0, 0.0);
+    glVertex3f(0.0, 1.5, 0.0);
+    // Z-axis (blue)
+    glColor3f(0.0, 0.0, 1.0);
+    glVertex3f(0.0, 0.0, 0.0);
+    glVertex3f(0.0, 0.0, 1.5);
+    glEnd();
+    glLineWidth(1.0f);
+}
+
 void ViewportWidget::drawCube()
 {
     glBegin(GL_QUADS);
diff --git a/src/ViewportWidget.h b/src/ViewportWidget.h
index d9e4771..4301f59 100644
--- a/src/ViewportWidget.h
+++ b/src/ViewportWidget.h
@@ -24,6 +24,8 @@ protected:
 
 private:
     void drawCube();
+    void drawViewCube();
+    void drawAxes();
 
     QMatrix4x4 projection;