Converting the laser beam example on ShaderToy to cocos2d-x shaders.

README.md

Laser beam example from Shader Toy https://www.shadertoy.com/view/XtBXW3

Usage: laserbeam.cpp - put this code inside the init method of a new project within HelloWorld.cpp. laserbeam.vert - put this in PROJECT_ROOT/Resources/res/ laserbeam.frag - put this in PROJECT_ROOT/Resources/res/

laserbeam.cpp

using std::string;
// custom shader similar to alpha test, but with normals and lighting
string kShaderKey("laser_rainbow");
auto glCache = GLProgramCache::getInstance();
auto prog = glCache->getGLProgram(kShaderKey.c_str());
if(! prog)
{
    prog = GLProgram::createWithFilenames("res/" + kShaderKey + ".vert",
                                          "res/" + kShaderKey + ".frag");
    glCache->addGLProgram(prog, kShaderKey);
}

// This is the display size of the quad where for the render beam (in pixels, not points)
Size texSize(400,80);

auto sprite = Sprite::create();//"res/laser_particle.png");
sprite->setPosition(Vec2(250,150));
//sprite->setAnchorPoint(Vec2::ANCHOR_MIDDLE);
sprite->setTextureRect(Rect(0, 0, texSize.width, texSize.height));
sprite->setBlendFunc(BlendFunc::ADDITIVE);


//auto glprogram = GLProgram::createWithFilenames("water.vsh", "water.fsh");
auto glprogramstate = GLProgramState::getOrCreateWithGLProgram(prog);
sprite->setGLProgramState(glprogramstate);

// note: iResolution is only "size of screen" because shadertoy applys to full view quad
auto scale_factor = Director::getInstance()->getContentScaleFactor();
Vec3 iResolution(texSize.width/(2.f / scale_factor),
                 texSize.height/(2.f / scale_factor),
                 scale_factor);
glprogramstate->setUniformVec3("iResolution", iResolution);

auto move = MoveBy::create(5.0f, Vec2(100,100));
auto seq = Sequence::create(move, move->reverse(), NULL);
sprite->runAction(RepeatForever::create(seq));
parent->addChild(sprite);

laserbeam.frag

// frag
uniform vec3 iResolution;
varying vec2 v_texCoord;
varying float iGlobalTime;

vec3 Strand(in vec2 fragCoord, in vec3 color, in float hoffset, in float hscale, in float vscale, in float timescale)
{
    float glow = 0.06 * iResolution.y;
    float twopi = 6.28318530718;
    float curve = 1.0 - abs(fragCoord.y - (sin(mod(fragCoord.x * hscale / 100.0 / iResolution.x * 1000.0 + iGlobalTime * timescale + hoffset, twopi)) * iResolution.y * 0.25 * vscale + iResolution.y / 2.0));
    float i = clamp(curve, 0.0, 1.0);
    i += clamp((glow + curve) / glow, 0.0, 1.0) * 0.4 ;
    return i * color;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    float timescale = 4.0;
    vec3 c = vec3(0, 0, 0);
    c += Strand(fragCoord, vec3(1.0, 0, 0), 0.7934 + 1.0 + sin(iGlobalTime) * 30.0, 1.0, 0.16, 10.0 * timescale);
    c += Strand(fragCoord, vec3(0.0, 1.0, 0.0), 0.645 + 1.0 + sin(iGlobalTime) * 30.0, 1.5, 0.2, 10.3 * timescale);
    c += Strand(fragCoord, vec3(0.0, 0.0, 1.0), 0.735 + 1.0 + sin(iGlobalTime) * 30.0, 1.3, 0.19, 8.0 * timescale);
    c += Strand(fragCoord, vec3(1.0, 1.0, 0.0), 0.9245 + 1.0 + sin(iGlobalTime) * 30.0, 1.6, 0.14, 12.0 * timescale);
    c += Strand(fragCoord, vec3(0.0, 1.0, 1.0), 0.7234 + 1.0 + sin(iGlobalTime) * 30.0, 1.9, 0.23, 14.0 * timescale);
    c += Strand(fragCoord, vec3(1.0, 0.0, 1.0), 0.84525 + 1.0 + sin(iGlobalTime) * 30.0, 1.2, 0.18, 9.0 * timescale);
    fragColor = vec4(c.r, c.g, c.b, 1.0);
}

void main(void)
{
    vec2 fragCoord = v_texCoord;
    mainImage(gl_FragColor.rgba, fragCoord); // gl_FragCoord.xy);
    gl_FragColor += vec4(0.6,0,0,0.6);
}

laserbeam.vert

attribute vec4 a_position;
attribute vec4 a_color;
attribute vec2 a_texCoord;

varying vec2 v_texCoord;
varying float iGlobalTime;

void main()
{
    // use CC_PMatrix not CC_MVPMatrix for 2D Sprites
    gl_Position = CC_PMatrix * a_position;
    v_texCoord = a_texCoord;
    iGlobalTime = CC_Time[1];
}