ofxVase

High-quality polyline rendering for openFrameworks with variable width, color, and smooth joints. Based on the VASE renderer algorithm by TSANG, Hao Fung for high-quality polyline tessellation.

Features

• Variable width - Each vertex can have a different stroke width
• Variable color - Per-vertex colors with smooth interpolation
• Joint styles - Round, Bevel, and Miter (with configurable limit)
• Cap styles - Round, Square, and Butt
• Catmull-Rom smoothing - Optional spline interpolation for silky curves
• Cross-platform - Uses openFrameworks' native mesh rendering

How It Works

ofxVase tessellates polylines into triangle meshes with proper geometry for:

• Variable-width strokes
• Rounded joints at turns (prevents gaps and overlaps)
• Semicircular end caps
• Per-vertex color interpolation

All rendering uses standard ofMesh, so it works everywhere openFrameworks does.

Usage

#include "ofxVase.h"

void ofApp::draw() {
    // Draw an ofPolyline with uniform width
    ofPolyline line;
    line.addVertex(100, 100);
    line.addVertex(200, 150);
    line.addVertex(300, 100);
    
    ofSetColor(255, 100, 100);
    ofxVase::draw(line, 10.0f);  // 10px width
}

Configure styles

void ofApp::setup() {
    ofxVase::setJointStyle(ofxVase::JointStyle::Round);
    ofxVase::setCapStyle(ofxVase::CapStyle::Round);
}

Variable width and color

void ofApp::draw() {
    std::vector<glm::vec2> points = {
        {100, 100}, {200, 200}, {300, 150}, {400, 200}
    };
    
    std::vector<ofFloatColor> colors = {
        ofFloatColor::red,
        ofFloatColor::yellow,
        ofFloatColor::green,
        ofFloatColor::blue
    };
    
    std::vector<float> widths = {5, 20, 10, 30};
    
    ofxVase::Options opts;
    opts.joint = ofxVase::JointStyle::Round;
    opts.cap = ofxVase::CapStyle::Round;
    
    ofxVase::Polyline poly(points, colors, widths, opts);
    
    ofEnableAlphaBlending();
    ofDisableDepthTest();  // Important for proper alpha blending
    poly.holder.toMesh().draw();
    ofEnableDepthTest();
}

Using the Renderer (recommended)

class ofApp : public ofBaseApp {
    ofxVase::Renderer renderer;
    
    void setup() {
        renderer.setup();
    }
    
    void draw() {
        ofxVase::Polyline poly(points, colors, widths, opts);
        
        renderer.begin();  // Enables alpha blending and depth test settings
        renderer.draw(poly);
        renderer.end();
    }
};

Smoothing (Catmull-Rom Splines)

Enable opts.smoothing = N to subdivide each segment N times using Catmull-Rom spline interpolation. This creates smooth curves from fewer control points:

opts.smoothing = 4;  // 4 subdivisions per segment = silky smooth curves

• 0 = no smoothing (default, straight lines between points)
• 1-2 = subtle smoothing
• 3-5 = smooth curves
• 6+ = very smooth (but more vertices)

Joint & Cap Styles

Joint Styles ✓

All three joint styles are fully implemented:

• Round - Smooth circular arc at turns (default)
• Bevel - Simple flat cut at turns
• Miter - Sharp pointed corners with configurable limit (opts.miterLimit, defaults to 4.0)

opts.joint = ofxVase::JointStyle::Round;  // or Bevel, or Miter
opts.miterLimit = 4.0f;  // Only affects Miter joints

Cap Styles ✓

• Round - Semicircular end caps (default)
• Square - Extended rectangular caps
• Butt - Flat caps with no extension

opts.cap = ofxVase::CapStyle::Round;  // or Square, or Butt

Wishlist / TODO

• [ ] Shader-based anti-aliasing - The original VASE renderer uses fragment shaders for feathered edges. We have the shaders in src/shaders/ but currently use mesh rendering for simplicity. Future: implement VBO path with shader-based AA.
• [ ] Feathering - Soft anti-aliased edges without MSAA (requires shader implementation)
• [ ] Performance optimization - Batch rendering, VBO caching for static polylines
• [ ] Dashed/dotted lines - Pattern support
• [ ] Gradient strokes - Texture coordinate generation for shader-based gradients

License

BSD 3-Clause License - See LICENSE.txt