Example with opengl triangle

examples/CMakeLists.txt

@@ -26,6 +26,15 @@ set_target_properties(
                LIBRARY_OUTPUT_DIRECTORY "${CMAKE_SOURCE_DIR}/out/${CMAKE_BUILD_TYPE}"
                RUNTIME_OUTPUT_DIRECTORY "${CMAKE_SOURCE_DIR}/out/${CMAKE_BUILD_TYPE}")
 
+add_executable(example_barycentric example_barycentric.cpp)
+set_target_properties(
+    example_barycentric
+    PROPERTIES CXX_STANDARD 23
+               ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_SOURCE_DIR}/out/${CMAKE_BUILD_TYPE}"
+               LIBRARY_OUTPUT_DIRECTORY "${CMAKE_SOURCE_DIR}/out/${CMAKE_BUILD_TYPE}"
+               RUNTIME_OUTPUT_DIRECTORY "${CMAKE_SOURCE_DIR}/out/${CMAKE_BUILD_TYPE}")
+target_link_libraries(example_barycentric PRIVATE omath::omath GLEW::GLEW glfw OpenGL::GL)
+
 find_package(OpenGL)
 find_package(GLEW REQUIRED)
 find_package(glfw3 CONFIG REQUIRED)

examples/example_barycentric.cpp

@@ -0,0 +1,332 @@
+#include <GL/glew.h>
+#include <GLFW/glfw3.h>
+#include <iostream>
+#include <vector>
+#include <cmath>
+#include <omath/omath.hpp>
+
+using omath::Vector3;
+using omath::Triangle;
+using omath::Color;
+
+static const char* vertexShaderSource = R"(
+#version 330 core
+layout (location = 0) in vec3 aPos;
+layout (location = 1) in vec3 aColor;
+layout (location = 2) in float aPointSize;
+layout (location = 3) in float aIsLine;
+
+out vec3 vColor;
+out float vIsLine;
+
+void main() {
+    gl_Position = vec4(aPos, 1.0);
+    vColor = aColor;
+    gl_PointSize = aPointSize;
+    vIsLine = aIsLine;
+}
+)";
+
+static const char* fragmentShaderSource = R"(
+#version 330 core
+in vec3 vColor;
+in float vIsLine;
+out vec4 FragColor;
+
+void main() {
+    if (vIsLine < 0.5) {
+        // Calculate distance from center of the point
+        vec2 coord = gl_PointCoord - vec2(0.5);
+        if(length(coord) > 0.5)
+            discard;
+    }
+
+    FragColor = vec4(vColor, 1.0);
+}
+)";
+
+GLuint compileShader(GLenum type, const char* src) {
+    GLuint shader = glCreateShader(type);
+    glShaderSource(shader, 1, &src, nullptr);
+    glCompileShader(shader);
+    GLint ok;
+    glGetShaderiv(shader, GL_COMPILE_STATUS, &ok);
+    if (!ok) {
+        char log[1024];
+        glGetShaderInfoLog(shader, sizeof(log), nullptr, log);
+        std::cerr << "Shader error: " << log << std::endl;
+    }
+    return shader;
+}
+
+void drawChar(char c, float x, float y, float scale, const Color& color, std::vector<float>& lines) {
+    float w = 0.5f * scale;
+    float h = 1.0f * scale;
+
+    auto add = [&](float x1, float y1, float x2, float y2) {
+        lines.push_back(x + x1*w); lines.push_back(y + y1*h); lines.push_back(0.0f);
+        lines.push_back(color.x); lines.push_back(color.y); lines.push_back(color.z);
+        lines.push_back(1.0f); // size
+        lines.push_back(1.0f); // isLine
+
+        lines.push_back(x + x2*w); lines.push_back(y + y2*h); lines.push_back(0.0f);
+        lines.push_back(color.x); lines.push_back(color.y); lines.push_back(color.z);
+        lines.push_back(1.0f); // size
+        lines.push_back(1.0f); // isLine
+    };
+
+    switch(c) {
+        case '0': add(0,0, 1,0); add(1,0, 1,1); add(1,1, 0,1); add(0,1, 0,0); break;
+        case '1': add(0.5f,0, 0.5f,1); add(0.25f,0.75f, 0.5f,1); add(0.25f,0, 0.75f,0); break;
+        case '2': add(0,1, 1,1); add(1,1, 1,0.5f); add(1,0.5f, 0,0.5f); add(0,0.5f, 0,0); add(0,0, 1,0); break;
+        case '3': add(0,1, 1,1); add(1,1, 1,0); add(1,0, 0,0); add(0,0.5f, 1,0.5f); break;
+        case '4': add(0,1, 0,0.5f); add(0,0.5f, 1,0.5f); add(1,1, 1,0); break;
+        case '5': add(1,1, 0,1); add(0,1, 0,0.5f); add(0,0.5f, 1,0.5f); add(1,0.5f, 1,0); add(1,0, 0,0); break;
+        case '6': add(1,1, 0,1); add(0,1, 0,0); add(0,0, 1,0); add(1,0, 1,0.5f); add(1,0.5f, 0,0.5f); break;
+        case '7': add(0,1, 1,1); add(1,1, 0.5f,0); break;
+        case '8': add(0,0, 1,0); add(1,0, 1,1); add(1,1, 0,1); add(0,1, 0,0); add(0,0.5f, 1,0.5f); break;
+        case '9': add(1,0.5f, 0,0.5f); add(0,0.5f, 0,1); add(0,1, 1,1); add(1,1, 1,0); add(1,0, 0,0); break;
+        case '.': add(0.4f,0, 0.6f,0); add(0.6f,0, 0.6f,0.2f); add(0.6f,0.2f, 0.4f,0.2f); add(0.4f,0.2f, 0.4f,0); break;
+    }
+}
+
+void drawText(const std::string& text, float x, float y, float scale, const Color& color, std::vector<float>& lines) {
+    float cursor = x;
+    for (char c : text) {
+        drawChar(c, cursor, y, scale, color, lines);
+        cursor += (c == '.' ? 0.3f : 0.7f) * scale;
+    }
+}
+
+GLFWwindow* initWindow(int width, int height, const char* title) {
+    if (!glfwInit()) {
+        std::cerr << "Failed to initialize GLFW\n";
+        return nullptr;
+    }
+
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
+    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+
+    GLFWwindow* window = glfwCreateWindow(width, height, title, NULL, NULL);
+    if (!window) { 
+        std::cerr << "Failed to create GLFW window\n";
+        glfwTerminate(); 
+        return nullptr; 
+    }
+    glfwMakeContextCurrent(window);
+
+    // Check if context is valid using standard GL
+    const GLubyte* renderer = glGetString(GL_RENDERER);
+    const GLubyte* version = glGetString(GL_VERSION);
+    if (renderer && version) {
+        std::cout << "Renderer: " << renderer << "\n";
+        std::cout << "OpenGL version supported: " << version << "\n";
+    } else {
+        std::cerr << "Failed to get GL_RENDERER or GL_VERSION. Context might be invalid.\n";
+    }
+
+    glewExperimental = GL_TRUE;
+    GLenum glewErr = glewInit();
+    if (glewErr != GLEW_OK) {
+        // Ignore GLEW_ERROR_NO_GLX_DISPLAY if we have a valid context (e.g. Wayland)
+        if (glewErr == GLEW_ERROR_NO_GLX_DISPLAY && renderer) {
+            std::cerr << "GLEW warning: " << glewGetErrorString(glewErr) << " (Ignored because context seems valid)\n";
+        } else {
+            std::cerr << "Failed to initialize GLEW: " << glewGetErrorString(glewErr) << "\n";
+            glfwTerminate();
+            return nullptr;
+        }
+    }
+    return window;
+}
+
+GLuint createShaderProgram() {
+    GLuint vs = compileShader(GL_VERTEX_SHADER, vertexShaderSource);
+    GLuint fs = compileShader(GL_FRAGMENT_SHADER, fragmentShaderSource);
+    GLuint shaderProgram = glCreateProgram();
+    glAttachShader(shaderProgram, vs);
+    glAttachShader(shaderProgram, fs);
+    glLinkProgram(shaderProgram);
+    return shaderProgram;
+}
+
+void generatePointCloud(std::vector<float>& pointCloud, const Triangle<Vector3<float>>& triangle) {
+    const auto& A = triangle.m_vertex1;
+    const auto& B = triangle.m_vertex2;
+    const auto& C = triangle.m_vertex3;
+    // Iterating over barycentric coordinates (u, v, w) from 0.0 to 1.0
+    for (float u = 0.0f; u <= 1.0f; u += 0.015f) {
+        for (float v = 0.0f; v <= 1.0f - u; v += 0.015f) {
+            float w = 1.0f - u - v;
+            if (w >= 0.0f && w <= 1.0f) {
+                Vector3<float> P = A * u + B * v + C * w;
+                pointCloud.push_back(P.x); pointCloud.push_back(P.y); pointCloud.push_back(P.z);
+                pointCloud.push_back(u);   pointCloud.push_back(v);   pointCloud.push_back(w);
+                pointCloud.push_back(2.0f); // size
+                pointCloud.push_back(0.0f); // isLine
+            }
+        }
+    }
+}
+
+void setupBuffers(GLuint& VAO_cloud, GLuint& VBO_cloud, const std::vector<float>& pointCloud, GLuint& VAO_dyn, GLuint& VBO_dyn) {
+    glGenVertexArrays(1, &VAO_cloud);
+    glGenBuffers(1, &VBO_cloud);
+    glBindVertexArray(VAO_cloud);
+    glBindBuffer(GL_ARRAY_BUFFER, VBO_cloud);
+    glBufferData(GL_ARRAY_BUFFER, pointCloud.size() * sizeof(float), pointCloud.data(), GL_STATIC_DRAW);
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
+    glEnableVertexAttribArray(0);
+    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
+    glEnableVertexAttribArray(1);
+    glVertexAttribPointer(2, 1, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
+    glEnableVertexAttribArray(2);
+    glVertexAttribPointer(3, 1, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(7 * sizeof(float)));
+    glEnableVertexAttribArray(3);
+
+    glGenVertexArrays(1, &VAO_dyn);
+    glGenBuffers(1, &VBO_dyn);
+    glBindVertexArray(VAO_dyn);
+    glBindBuffer(GL_ARRAY_BUFFER, VBO_dyn);
+    glBufferData(GL_ARRAY_BUFFER, 1000 * 8 * sizeof(float), NULL, GL_DYNAMIC_DRAW); 
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
+    glEnableVertexAttribArray(0);
+    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
+    glEnableVertexAttribArray(1);
+    glVertexAttribPointer(2, 1, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
+    glEnableVertexAttribArray(2);
+    glVertexAttribPointer(3, 1, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(7 * sizeof(float)));
+    glEnableVertexAttribArray(3);
+}
+
+void updateDynamicData(std::vector<float>& dynData, float u, float v, float w, const Vector3<float>& P, const Triangle<Vector3<float>>& triangle) {
+    const auto& A = triangle.m_vertex1;
+    const auto& B = triangle.m_vertex2;
+    const auto& C = triangle.m_vertex3;
+
+    float sizeA = 10.0f + u * 30.0f;
+    float sizeB = 10.0f + v * 30.0f;
+    float sizeC = 10.0f + w * 30.0f;
+    float sizeP = 12.0f;
+
+    dynData = {
+        // Lines from P to A, B, C
+        P.x, P.y, P.z, u, v, w, 1.0f, 1.0f,
+        A.x, A.y, A.z, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
+
+        P.x, P.y, P.z, u, v, w, 1.0f, 1.0f,
+        B.x, B.y, B.z, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f,
+
+        P.x, P.y, P.z, u, v, w, 1.0f, 1.0f,
+        C.x, C.y, C.z, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f,
+
+        // The animated dot itself (White)
+        P.x, P.y, P.z, 1.0f, 1.0f, 1.0f, sizeP, 0.0f,
+
+        // The 3 corner dots
+        A.x, A.y, A.z, 1.0f, 0.0f, 0.0f, sizeA, 0.0f,
+        B.x, B.y, B.z, 0.0f, 1.0f, 0.0f, sizeB, 0.0f,
+        C.x, C.y, C.z, 0.0f, 0.0f, 1.0f, sizeC, 0.0f
+    };
+
+    char bufA[16], bufB[16], bufC[16];
+    snprintf(bufA, sizeof(bufA), "%.2f", u);
+    snprintf(bufB, sizeof(bufB), "%.2f", v);
+    snprintf(bufC, sizeof(bufC), "%.2f", w);
+
+    // Keep text at a fixed distance from the dots
+    float distA = 0.13f;
+    float distB = 0.13f;
+    float distC = 0.13f;
+
+    drawText(bufA, A.x - 0.05f, A.y + distA, 0.1f, Color(1,0,0,1), dynData);
+    drawText(bufB, B.x - 0.15f - distB, B.y - 0.05f - distB, 0.1f, Color(0,1,0,1), dynData);
+    drawText(bufC, C.x + 0.05f + distC, C.y - 0.05f - distC, 0.1f, Color(0,0,1,1), dynData);
+}
+
+int main() {
+    GLFWwindow* window = initWindow(800, 800, "Barycentric Coordinates");
+    if (!window) return -1;
+
+    GLuint shaderProgram = createShaderProgram();
+
+    // Triangle vertices as shown in the picture (Red, Green, Blue)
+    // Scaled down slightly to leave room for text
+    Triangle<Vector3<float>> triangle(
+        Vector3<float>(0.0f, 0.6f, 0.0f),   // Red dot (top)
+        Vector3<float>(-0.6f, -0.6f, 0.0f), // Green dot (bottom left)
+        Vector3<float>(0.6f, -0.6f, 0.0f)   // Blue dot (bottom right)
+    );
+
+    std::vector<float> pointCloud;
+    generatePointCloud(pointCloud, triangle);
+
+    GLuint VAO_cloud, VBO_cloud, VAO_dyn, VBO_dyn;
+    setupBuffers(VAO_cloud, VBO_cloud, pointCloud, VAO_dyn, VBO_dyn);
+
+    glEnable(GL_PROGRAM_POINT_SIZE);
+    glEnable(GL_BLEND);
+    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+    while (!glfwWindowShouldClose(window)) {
+        glClearColor(0.02f, 0.02f, 0.02f, 1.0f);
+        glClear(GL_COLOR_BUFFER_BIT);
+
+        glUseProgram(shaderProgram);
+
+        // Draw the point cloud (the iterated points)
+        glBindVertexArray(VAO_cloud);
+        glDrawArrays(GL_POINTS, 0, pointCloud.size() / 8);
+
+        // Animate the white dot to simulate dragging
+        float t = glfwGetTime();
+        float u = (std::sin(t * 1.5f) * 0.5f + 0.5f);
+        float v = (std::cos(t * 1.1f) * 0.5f + 0.5f);
+
+        if (u + v > 1.0f) {
+            u = 1.0f - u;
+            v = 1.0f - v;
+        }
+        float w = 1.0f - u - v;
+
+        if (w > 1.0f) {
+            float diff = w - 1.0f;
+            w = 1.0f;
+            u += diff / 2.0f;
+            v += diff / 2.0f;
+        } else if (w < 0.0f) {
+            float diff = -w;
+            w = 0.0f;
+            u -= diff / 2.0f;
+            v -= diff / 2.0f;
+        }
+
+        Vector3<float> P = triangle.m_vertex1 * u + triangle.m_vertex2 * v + triangle.m_vertex3 * w;
+
+        std::vector<float> dynData;
+        updateDynamicData(dynData, u, v, w, P, triangle);
+
+        glBindVertexArray(VAO_dyn);
+        glBindBuffer(GL_ARRAY_BUFFER, VBO_dyn);
+        glBufferSubData(GL_ARRAY_BUFFER, 0, dynData.size() * sizeof(float), dynData.data());
+
+        // Draw lines
+        glDrawArrays(GL_LINES, 0, 6);
+
+        // Draw text lines
+        int numTextVertices = (dynData.size() / 8) - 10;
+        if (numTextVertices > 0) {
+            glDrawArrays(GL_LINES, 10, numTextVertices);
+        }
+
+        // Draw dots
+        glDrawArrays(GL_POINTS, 6, 4);
+
+        glfwSwapBuffers(window);
+        glfwPollEvents();
+    }
+
+    glfwTerminate();
+    return 0;
+}