feat: Add Blinn-Phong shading for faces

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

resources.qrc

@@ -14,5 +14,7 @@
         <file alias="simple.frag">src/shaders/simple.frag</file>
         <file alias="texture.vert">src/shaders/texture.vert</file>
         <file alias="texture.frag">src/shaders/texture.frag</file>
+        <file alias="lit.vert">src/shaders/lit.vert</file>
+        <file alias="lit.frag">src/shaders/lit.frag</file>
     </qresource>
 </RCC>

src/ViewportWidget.cpp

@@ -36,6 +36,8 @@
 #include <TopoDS_Face.hxx>
 #include <Poly_Triangulation.hxx>
 #include <BRep_Tool.hxx>
+#include <gp_Dir.hxx>
+#include <gp_Trsf.hxx>
 
 struct PntComparator {
     bool operator()(const gp_Pnt& a, const gp_Pnt& b) const {
@@ -79,6 +81,7 @@ ViewportWidget::~ViewportWidget()
 {
     makeCurrent();
     delete m_shaderProgram;
+    delete m_litShaderProgram;
     delete m_viewCube;
     delete m_sketchGrid;
     m_vbo.destroy();
@@ -601,6 +604,9 @@ void ViewportWidget::drawSketch(const SketchFeature* sketch)
 
     if (!lineVertices.isEmpty()) {
         m_vbo.allocate(lineVertices.constData(), lineVertices.size() * sizeof(GLfloat));
+        m_shaderProgram->enableAttributeArray(0);
+        m_shaderProgram->setAttributeBuffer(0, GL_FLOAT, 0, 3, 0);
+        m_shaderProgram->disableAttributeArray(1);
         glDrawArrays(GL_LINES, 0, lineVertices.size() / 3);
     }
 
@@ -658,9 +664,9 @@ void ViewportWidget::drawSketch(const SketchFeature* sketch)
 
     // Draw faces
     if (!sketch->shape().IsNull()) {
-        BRepMesh_IncrementalMesh(sketch->shape(), 0.1); // Linear deflection
+        BRepMesh_IncrementalMesh(sketch->shape(), 0.1, Standard_False, 0.5, Standard_True); // Linear deflection, compute normals
 
-        QVector<GLfloat> faceVertices;
+        QVector<GLfloat> faceData;
         TopExp_Explorer explorer(sketch->shape(), TopAbs_FACE);
         for (; explorer.More(); explorer.Next()) {
             TopoDS_Face face = TopoDS::Face(explorer.Current());
@@ -668,26 +674,62 @@ void ViewportWidget::drawSketch(const SketchFeature* sketch)
             Handle(Poly_Triangulation) triangulation = BRep_Tool::Triangulation(face, location);
 
             if (!triangulation.IsNull()) {
+                gp_Trsf locTrsf = location.Transformation();
+
+                if (triangulation->HasNormals()) {
+                    for (int i = 1; i <= triangulation->NbTriangles(); ++i) {
+                        const Poly_Triangle& triangle = triangulation->Triangle(i);
+                        for (int j = 1; j <= 3; ++j) {
+                            int nodeIdx = triangle.Value(j);
+                            gp_Pnt p = triangulation->Node(nodeIdx).Transformed(location);
+                            gp_Dir n = triangulation->Normal(nodeIdx);
+                            n.Transform(locTrsf);
+
+                            if (face.Orientation() == TopAbs_REVERSED) {
+                                n.Reverse();
+                            }
+                            faceData << p.X() << p.Y() << p.Z();
+                            faceData << n.X() << n.Y() << n.Z();
+                        }
+                    }
+                } else {
                     for (int i = 1; i <= triangulation->NbTriangles(); ++i) {
                         const Poly_Triangle& triangle = triangulation->Triangle(i);
                         gp_Pnt p1 = triangulation->Node(triangle.Value(1)).Transformed(location);
                         gp_Pnt p2 = triangulation->Node(triangle.Value(2)).Transformed(location);
                         gp_Pnt p3 = triangulation->Node(triangle.Value(3)).Transformed(location);
-                    faceVertices << p1.X() << p1.Y() << p1.Z();
+
-                    faceVertices << p2.X() << p2.Y() << p2.Z();
+                        QVector3D v1(p1.X(), p1.Y(), p1.Z());
-                    faceVertices << p3.X() << p3.Y() << p3.Z();
+                        QVector3D v2(p2.X(), p2.Y(), p2.Z());
+                        QVector3D v3(p3.X(), p3.Y(), p3.Z());
+                        QVector3D faceNormal = QVector3D::crossProduct(v2 - v1, v3 - v1).normalized();
+                        if (face.Orientation() == TopAbs_REVERSED) {
+                            faceNormal = -faceNormal;
+                        }
+                        faceData << p1.X() << p1.Y() << p1.Z() << faceNormal.x() << faceNormal.y() << faceNormal.z();
+                        faceData << p2.X() << p2.Y() << p2.Z() << faceNormal.x() << faceNormal.y() << faceNormal.z();
+                        faceData << p3.X() << p3.Y() << p3.Z() << faceNormal.x() << faceNormal.y() << faceNormal.z();
+                    }
                 }
             }
         }
 
-        if (!faceVertices.isEmpty()) {
+        if (!faceData.isEmpty()) {
-            glEnable(GL_BLEND);
+            m_litShaderProgram->bind();
-            glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+            m_litShaderProgram->setUniformValue(m_litProjMatrixLoc, projection);
-            m_shaderProgram->setUniformValue(m_colorLoc, QVector4D(0.5f, 0.5f, 1.0f, 0.5f));
+            m_litShaderProgram->setUniformValue(m_litMvMatrixLoc, m_camera->modelViewMatrix());
+            m_litShaderProgram->setUniformValue(m_litNormalMatrixLoc, m_camera->modelViewMatrix().normalMatrix());
+
             m_vbo.bind();
-            m_vbo.allocate(faceVertices.constData(), faceVertices.size() * sizeof(GLfloat));
+            m_vbo.allocate(faceData.constData(), faceData.size() * sizeof(GLfloat));
-            glDrawArrays(GL_TRIANGLES, 0, faceVertices.size() / 3);
+
-            glDisable(GL_BLEND);
+            m_litShaderProgram->enableAttributeArray(0);
+            m_litShaderProgram->setAttributeBuffer(0, GL_FLOAT, 0, 3, 6 * sizeof(GLfloat));
+            m_litShaderProgram->enableAttributeArray(1);
+            m_litShaderProgram->setAttributeBuffer(1, GL_FLOAT, 3 * sizeof(GLfloat), 3, 6 * sizeof(GLfloat));
+
+            glDrawArrays(GL_TRIANGLES, 0, faceData.size() / 6);
+            m_shaderProgram->bind(); // rebind simple shader for subsequent draws
         }
     }
 
@@ -696,8 +738,8 @@ void ViewportWidget::drawSketch(const SketchFeature* sketch)
 
 void ViewportWidget::initShaders()
 {
+    // Simple shader for lines and grids
     m_shaderProgram = new QOpenGLShaderProgram(this);
-
     if (!m_shaderProgram->addShaderFromSourceFile(QOpenGLShader::Vertex, ":/shaders/simple.vert")) {
         qCritical() << "Vertex shader compilation failed:" << m_shaderProgram->log();
         return;
@@ -710,10 +752,27 @@ void ViewportWidget::initShaders()
         qCritical() << "Shader program linking failed:" << m_shaderProgram->log();
         return;
     }
-
     m_projMatrixLoc = m_shaderProgram->uniformLocation("projectionMatrix");
     m_mvMatrixLoc = m_shaderProgram->uniformLocation("modelViewMatrix");
     m_colorLoc = m_shaderProgram->uniformLocation("objectColor");
+
+    // Lit shader for faces
+    m_litShaderProgram = new QOpenGLShaderProgram(this);
+    if (!m_litShaderProgram->addShaderFromSourceFile(QOpenGLShader::Vertex, ":/shaders/lit.vert")) {
+        qCritical() << "Lit vertex shader compilation failed:" << m_litShaderProgram->log();
+        return;
+    }
+    if (!m_litShaderProgram->addShaderFromSourceFile(QOpenGLShader::Fragment, ":/shaders/lit.frag")) {
+        qCritical() << "Lit fragment shader compilation failed:" << m_litShaderProgram->log();
+        return;
+    }
+    if (!m_litShaderProgram->link()) {
+        qCritical() << "Lit shader program linking failed:" << m_litShaderProgram->log();
+        return;
+    }
+    m_litProjMatrixLoc = m_litShaderProgram->uniformLocation("projectionMatrix");
+    m_litMvMatrixLoc = m_litShaderProgram->uniformLocation("modelViewMatrix");
+    m_litNormalMatrixLoc = m_litShaderProgram->uniformLocation("normalMatrix");
 }
 
 void ViewportWidget::drawSelectionPlanes()

src/ViewportWidget.h

@@ -97,6 +97,7 @@ private:
 
     QMatrix4x4 projection;
     QOpenGLShaderProgram* m_shaderProgram = nullptr;
+    QOpenGLShaderProgram* m_litShaderProgram = nullptr;
     QOpenGLVertexArrayObject m_vao;
     QOpenGLBuffer m_vbo;
 
@@ -104,6 +105,11 @@ private:
     int m_projMatrixLoc = -1;
     int m_mvMatrixLoc = -1;
     int m_colorLoc = -1;
+
+    // Lit shader uniform locations
+    int m_litProjMatrixLoc = -1;
+    int m_litMvMatrixLoc = -1;
+    int m_litNormalMatrixLoc = -1;
     Camera* m_camera = nullptr;
     ViewCube* m_viewCube;
     SketchGrid* m_sketchGrid = nullptr;

src/shaders/lit.frag

@@ -0,0 +1,33 @@
+#version 330 core
+out vec4 FragColor;
+
+in vec3 FragPos;
+in vec3 Normal;
+
+void main()
+{
+    vec3 viewPos = vec3(0.0, 0.0, 0.0); // View position is origin in view space
+    vec3 lightPos = vec3(0.0, 10.0, 5.0); // Light position in view space
+    vec3 lightColor = vec3(1.0, 1.0, 1.0);
+    vec3 objectColor = vec3(0.5, 0.5, 1.0);
+
+    // Ambient
+    float ambientStrength = 0.3;
+    vec3 ambient = ambientStrength * lightColor;
+
+    // Diffuse
+    vec3 norm = normalize(Normal);
+    vec3 lightDir = normalize(lightPos - FragPos);
+    float diff = max(dot(norm, lightDir), 0.0);
+    vec3 diffuse = diff * lightColor;
+
+    // Specular
+    float specularStrength = 0.5;
+    vec3 viewDir = normalize(viewPos - FragPos);
+    vec3 reflectDir = reflect(-lightDir, norm);
+    float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32);
+    vec3 specular = specularStrength * spec * lightColor;
+
+    vec3 result = (ambient + diffuse + specular) * objectColor;
+    FragColor = vec4(result, 1.0);
+}

src/shaders/lit.vert

@@ -0,0 +1,17 @@
+#version 330 core
+layout (location = 0) in vec3 aPos;
+layout (location = 1) in vec3 aNormal;
+
+out vec3 FragPos;
+out vec3 Normal;
+
+uniform mat4 modelViewMatrix;
+uniform mat4 projectionMatrix;
+uniform mat3 normalMatrix;
+
+void main()
+{
+    FragPos = vec3(modelViewMatrix * vec4(aPos, 1.0));
+    Normal = normalMatrix * aNormal;
+    gl_Position = projectionMatrix * modelViewMatrix * vec4(aPos, 1.0);
+}