Simple demo to compare drawing 2D triangles with Cinder's VBO and TriMesh wrappers

TestMeshApp.cpp

// Simple demo to compare drawing 2D triangles with Cinder's VBO and TriMesh wrappers.
// https://drewish.com/2014/08/16/comparing-the-trimesh-and-vbomesh-in-cinder/

#include "cinder/app/AppBasic.h"
#include "cinder/gl/gl.h"
#include "cinder/gl/Vbo.h"
#include "cinder/Trimesh.h"
#include "cinder/params/Params.h"

using namespace ci;
using namespace ci::app;
using namespace std;

// sqrt(3) / 2
#define M_SQRT_3_2 0.8660254037844386

class MeshTestApp : public AppBasic {
public:
    void prepareSettings( Settings *settings ) override;
    void setup();
    void recalculate();
    void buildVBOMesh();
    void buildTriMesh();
    void draw();

    gl::VboMesh mMesh;
    TriMesh mTriangles;
    params::InterfaceGl mParams;

    int  mCols = 10;
    int  mRows = 10;
    int  mScale = 30;
    bool mWireframe = false;
    bool useTriMesh = false;
};

void MeshTestApp::prepareSettings( Settings *settings )
{
    settings->enableHighDensityDisplay();
    settings->enableMultiTouch( false );
}

void MeshTestApp::setup()
{
    mParams = params::InterfaceGl( "Parameters", Vec2i( 220, 170 ) );
    mParams.addParam( "Scale", &mScale )
        .keyIncr( "s" ).keyDecr( "S" )
        .min( 1 ).max( 100 ).step( 1 )
        .updateFn( [this] { recalculate(); } );
    mParams.addParam( "Columns", &mCols )
        .keyIncr( "d" ).keyDecr( "D" )
        .min( 1 ).max( 100 ).step( 1 )
        .updateFn( [this] { recalculate(); } );
    mParams.addParam( "Rows", &mRows )
        .keyIncr( "f" ).keyDecr( "F" )
        .min( 1 ).max( 100 ).step( 1 )
        .updateFn( [this] { recalculate(); } );

    mParams.addParam( "Wireframe", &mWireframe )
        .key( "w" );
    mParams.addParam( "TriMesh/VBO", &useTriMesh )
        .updateFn( [this] { recalculate(); } )
        .key( "t" );

    recalculate();
}

void MeshTestApp::recalculate()
{
    if (useTriMesh) buildTriMesh();
    else buildVBOMesh();
}

void MeshTestApp::buildVBOMesh()
{
    gl::VboMesh::Layout layout;
    layout.setStaticIndices();
    layout.setStaticPositions();
    layout.setStaticColorsRGB();

    mMesh = gl::VboMesh(mCols * mRows * 3, mCols * mRows * 3, layout, GL_TRIANGLES);
    vector<uint32_t> indices;
    vector<Vec3f> positions;
    vector<Color> colors;

    float w = M_SQRT_3_2 * mScale;
    float h = 1.0 * mScale;
    int index = -1;
    Color8u color;

    for (int col = 0; col < mCols; col++) {
        float x = col * 2 * w;
        int direction = (col % 2) ? 1 : -1;
        for (int row = 0; row < mRows; row++) {
            direction *= -1;
            float y = row * h;

            positions.push_back( Vec3f( x - w * direction, y - h, 0 ) );
            positions.push_back( Vec3f( x + w * direction, y + 0, 0 ) );
            positions.push_back( Vec3f( x - w * direction, y + h, 0 ) );

            // #69D2E7 and #A7DBD8
            color = (direction > 0) ? Color8u( 105,210,231 ) : Color8u( 224,228,204 );
            colors.push_back( color );
            colors.push_back( color );
            colors.push_back( color );

            index += 3;
            indices.push_back( index - 2 );
            indices.push_back( index - 1 );
            indices.push_back( index );
        }
    }
    mMesh.bufferIndices( indices );
    mMesh.bufferPositions( positions );
    mMesh.bufferColorsRGB( colors );
}

void MeshTestApp::buildTriMesh()
{
    float w = M_SQRT_3_2 * mScale;
    float h = 1.0 * mScale;
    int index = -1;
    Color color;

    mTriangles.clear();

    for (int col = 0; col < mCols; col++) {
        float x = col * 2 * w;
        int direction = (col % 2) ? 1 : -1;
        for (int row = 0; row < mRows; row++) {
            direction *= -1;
            float y = row * h;

            mTriangles.appendVertex( Vec3f( x - w * direction, y - h, 0 ) );
            mTriangles.appendVertex( Vec3f( x + w * direction, y + 0, 0 ) );
            mTriangles.appendVertex( Vec3f( x - w * direction, y + h, 0 ) );

            // #69D2E7 and #A7DBD8
            color = (direction > 0) ? Color8u( 250,105,0 ) : Color8u( 105,210,231 );
            mTriangles.appendColorRgb( color );
            mTriangles.appendColorRgb( color );
            mTriangles.appendColorRgb( color );

            index += 3;
            mTriangles.appendTriangle( index - 2, index - 1, index );
        }
    }
}

void MeshTestApp::draw()
{
    gl::pushModelView();
    gl::clear( Color::white() );

    if (mWireframe) gl::enableWireframe();

    if (useTriMesh)
        gl::draw( mTriangles );
    else
        gl::draw( mMesh );

    if (mWireframe) gl::disableWireframe();

    gl::popModelView();

    mParams.draw();
}

CINDER_APP_BASIC( MeshTestApp, RendererGl )