I’m working on rendering a cylinder in OpenGL, and I’m facing an issue with texture mapping. I’m trying to map a texture onto the curved surface of the cylinder, but the texture appears distorted where it connects.

Here’s how I’m generating the vertices and setting up the attribute pointers:

std::vector<float> CylinderVertices(float bottomRadius, float topRadius, float height, int numSegments) {
    std::vector<float> vertices;

    // Generate vertices for the sides of the cylinder
    for (int i = 0; i < numSegments; ++i) {
        float theta1 = 2.0 * M_PI * i / numSegments;
        float theta2 = 2.0 * M_PI * (i + 1) / numSegments;

        float x1_bottom = bottomRadius * cos(theta1);
        float z1_bottom = bottomRadius * sin(theta1);
        float x2_bottom = bottomRadius * cos(theta2);
        float z2_bottom = bottomRadius * sin(theta2);

        float x1_top = topRadius * cos(theta1);
        float z1_top = topRadius * sin(theta1);
        float x2_top = topRadius * cos(theta2);
        float z2_top = topRadius * sin(theta2);

        // Texture coordinates
        // Texture coordinates
        float u1 = static_cast<float>(i) / numSegments; // Left side of the quad
        float u2 = static_cast<float>(i + 1) / numSegments; // Right side of the quad

        // Scale the texture coordinates to fit the entire texture onto the cylinder
        u1 *= 2.0f * M_PI * bottomRadius; 
        u2 *= 2.0f * M_PI * topRadius;


        // Vertices for the first triangle of the side quad
        vertices.push_back(x1_bottom);  // Position
        vertices.push_back(-height / 2.0f);
        vertices.push_back(z1_bottom);
        vertices.push_back(u1);         // Texture coordinates
        vertices.push_back(0.0f);

        vertices.push_back(x1_top);
        vertices.push_back(height / 2.0f);
        vertices.push_back(z1_top);
        vertices.push_back(u1);
        vertices.push_back(1.0f);

        vertices.push_back(x2_bottom);
        vertices.push_back(-height / 2.0f);
        vertices.push_back(z2_bottom);
        vertices.push_back(u2);
        vertices.push_back(0.0f);

        // Vertices for the second triangle of the side quad
        vertices.push_back(x2_bottom);
        vertices.push_back(-height / 2.0f);
        vertices.push_back(z2_bottom);
        vertices.push_back(u2);
        vertices.push_back(0.0f);

        vertices.push_back(x1_top);
        vertices.push_back(height / 2.0f);
        vertices.push_back(z1_top);
        vertices.push_back(u1);
        vertices.push_back(1.0f);

        vertices.push_back(x2_top);
        vertices.push_back(height / 2.0f);
        vertices.push_back(z2_top);
        vertices.push_back(u2);
        vertices.push_back(1.0f);
    }

    return vertices;
}

VAO1.Bind();
VBO VBO1(cylinderVertices.data(), cylinderVertices.size() * sizeof(float));
// Position attribute
VAO1.LinkAttrib(VBO1, 0, 3, GL_FLOAT, 5 * sizeof(float), (void*)0);
// Color attribute
VAO1.LinkAttrib(VBO1, 1, 3, GL_FLOAT, 5 * sizeof(float), (void*)0);
// Texture coordinate attribute
VAO1.LinkAttrib(VBO1, 2, 3, GL_FLOAT, 5 * sizeof(float), (void*)0);
// Light attribute
VAO1.LinkAttrib(VBO1, 3, 3, GL_FLOAT, 5 * sizeof(float), (void*)0);
VAO1.Unbind();
VBO1.Unbind();

I’ve tried adjusting the texture coordinates to scale based on the circumference of the cylinder, as shown in the code snippet above. Additionally, I’ve double-checked the vertex data layout and the attribute setup to ensure they are correct.

I was expecting the texture to be mapped onto the curved surface of the cylinder without distortion or enlargement. Specifically, I wanted the texture to wrap around the cylinder smoothly, following its curvature accurately.

Can someone help me understand what I’m doing wrong? How can I properly map the texture onto the cylinder without distortion or enlargement?

Additional Information:

I’m using GLFW and GLEW for window and context management.
The vertex data layout contains position, color, texture coordinate, and light data for each vertex.

Problem