Static Fire and Haze

            
              var fireVertexShader = `
attribute vec4 orientation;
attribute vec3 offset;
attribute vec2 scale;
attribute float life;
attribute float random;

varying vec2 vUv;
varying float vRandom;
varying float vAlpha;

float range(float oldValue, float oldMin, float oldMax, float newMin, float newMax) {
    float oldRange = oldMax - oldMin;
    float newRange = newMax - newMin;
    return (((oldValue - oldMin) * newRange) / oldRange) + newMin;
}

// From Inigo Quilez http://www.iquilezles.org/www/articles/functions/functions.htm
float pcurve(float x, float a, float b) {
    float k = pow(a + b, a + b) / (pow(a, a) * pow(b, b));
    return k * pow(x, a) * pow(1.0 - x, b);
}

void main() {
    vUv = uv;
    vRandom = random;

    vAlpha = pcurve(life, 1.0, 2.0);

    vec3 pos = position;

    pos.xy *= scale * vec2(range(pow(life, 1.5), 0.0, 1.0, 1.0, 0.6), range(pow(life, 1.5), 0.0, 1.0, 0.6, 1.2));

    vec4 or = orientation;
    vec3 vcV = cross(or.xyz, pos);
    pos = vcV * (2.0 * or.w) + (cross(or.xyz, vcV) * 2.0 + pos);

    gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0);
}
`;
    
var fireFragmentShader = `
uniform sampler2D uMap;
uniform vec3 uColor1;
uniform vec3 uColor2;
uniform float uTime;

varying vec2 vUv;
varying float vAlpha;
varying float vRandom;

void main() {
    vec2 uv = vUv;

    float spriteLength = 10.0;
    uv.x /= spriteLength;
    float spriteIndex = mod(uTime * 0.1 + vRandom * 2.0, 1.0);
    uv.x += floor(spriteIndex * spriteLength) / spriteLength;

    vec4 map = texture2D(uMap, uv);

    gl_FragColor.rgb = mix(uColor2, uColor1, map.r);
    gl_FragColor.a = vAlpha * map.a;
}
`;

var embersVertexShader = `
attribute float size;
attribute float life;
attribute vec3 offset;

varying float vAlpha;

// From Inigo Quilez http://www.iquilezles.org/www/articles/functions/functions.htm
float impulse(float k, float x) {
    float h = k * x;
    return h * exp(1.0 - h);
}

void main() {
    vAlpha = impulse(6.28, life);

    vec3 pos = position;
    pos += offset * vec3(life * 0.7 + 0.3, life * 0.9 + 0.1, life * 0.7 + 0.3);

    vec4 mvPosition = modelViewMatrix * vec4(pos, 1.0);
    gl_PointSize = size * (80.0 / length(mvPosition.xyz));
    gl_Position = projectionMatrix * mvPosition;
}
`;

var embersFragmentShader = `
uniform sampler2D uMap;
uniform vec3 uColor;

varying float vAlpha;

void main() {
    vec2 uv = vec2(gl_PointCoord.x, 1.0 - gl_PointCoord.y);
    vec4 mask = texture2D(uMap, uv);

    gl_FragColor.rgb = uColor;
    gl_FragColor.a = mask.a * vAlpha * 0.8;
}
`;

var hazeVertexShader = `
attribute vec3 base;
attribute vec3 offset;
attribute vec4 orientation;
attribute vec2 scale;
attribute float life;

varying float vAlpha;
varying vec2 vUv;

// From Inigo Quilez http://www.iquilezles.org/www/articles/functions/functions.htm
float impulse(float k, float x) {
    float h = k * x;
    return h * exp(1.0 - h);
}

float pcurve(float x, float a, float b) {
    float k = pow(a + b, a + b) / (pow(a, a) * pow(b, b));
    return k * pow(x, a) * pow(1.0 - x, b);
}

void main() {
    vUv = uv;
    vAlpha = pcurve(life, 1.0, 2.0);

    vec3 pos = position;

    pos.xy *= scale * (life * 0.7 + 0.3);

    vec4 or = orientation;
    vec3 vcV = cross(or.xyz, pos);
    pos = vcV * (2.0 * or.w) + (cross(or.xyz, vcV) * 2.0 + pos);

    pos += base;
    pos += offset * vec3(life * 0.7 + 0.3, life * 0.9 + 0.1, life * 0.7 + 0.3);

    gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0);;
}
`;

var hazeFragmentShader = `
uniform sampler2D uMap;
uniform sampler2D uMask;
uniform vec2 uResolution;

varying float vAlpha;
varying vec2 vUv;

void main() {
    vec2 uv = gl_FragCoord.xy / uResolution;
    vec2 mask = texture2D(uMask, vUv).ra - vec2(0.5);
    uv -= mask * 0.1;
    vec4 tex = texture2D(uMap, uv);

    gl_FragColor.rgb = tex.rgb;
    gl_FragColor.a = vAlpha * 0.5;
}
`;

(function() {
    var _renderer, _scene, _camera, _controls, _rtt;
    var _width, _height;
    
    window.onload = init;
    
    function init() {
        initWorld();
        initScene();
    }
    
    //=====// Utils //========================================//     

    function random(min, max, precision) {
        var p = Math.pow(10, precision);
        return Math.round((min + Math.random() * (max - min)) * p) / p;
    }

    //=====// World //========================================//     
        
    function initWorld() {
        _renderer = new THREE.WebGLRenderer();
        _renderer.setPixelRatio(2);
        _renderer.setSize(window.innerWidth, window.innerHeight);
        _renderer.setClearColor(0x000000);
        document.body.appendChild(_renderer.domElement);
        
        _scene = new THREE.Scene();
        
        _camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 1000);        
        _camera.position.set(0, 0, 4);
        _camera.target = new THREE.Vector3();
        _camera.lookAt(_camera.target);

        _controls = new THREE.OrbitControls(_camera);
        _controls.enableDamping = true;
        _controls.dampingFactor = 0.1;
        _controls.rotateSpeed = 0.1;
        
        window.addEventListener('resize', resize, false);
        resize();
        requestAnimationFrame(render);
    }

    function resize() {
        _width = window.innerWidth;
        _height = window.innerHeight;
        _renderer.setSize(_width, _height);
        _camera.aspect = _width / _height;
        _camera.updateProjectionMatrix();
        resetRT();
    }

    function resetRT() {
        var _parameters = {minFilter: THREE.LinearFilter, magFilter: THREE.LinearFilter, format: THREE.RGBAFormat, stencilBuffer: false};
        if (_rtt) _rtt.dispose();
        _rtt = new THREE.WebGLRenderTarget(_width * 0.5, _height * 0.5, _parameters);
    }

    function render() {
        requestAnimationFrame(render);
        if (_controls) _controls.update();
        _renderer.render(_scene, _camera);
    }
    
    //=====// Scene //========================================//     
    
    function initScene() {
        initBackground();
        initFire();
        initEmbers();
        initHaze();
    }

    function initBackground() {
        var background = new THREE.Mesh(
            new THREE.BoxBufferGeometry(4, 4, 4),
            new THREE.MeshBasicMaterial({side: THREE.BackSide})
        );
        _scene.add(background);

        var textureLoader = new THREE.TextureLoader();
        textureLoader.load('https://cinemont.com/tutorials/zelda/rock.jpg', t => {background.material.map = t, background.material.needsUpdate = true});
    }

    //=====// Fire //========================================//     

    function initFire() {
        var _geometry, _shader, _mesh, _group;
        var _num = 8;

        (function() {
            initGeometry();
            initInstances();
            initShader();
            initMesh();
            requestAnimationFrame(loop);
        })();    

        function initGeometry() {
            _geometry = new THREE.InstancedBufferGeometry();
            _geometry.maxInstancedCount = _num;

            var shape = new THREE.PlaneBufferGeometry(1, 1);
            shape.translate(0, 0.4, 0);
            var data = shape.attributes;

            _geometry.addAttribute('position', new THREE.BufferAttribute(new Float32Array(data.position.array), 3));
            _geometry.addAttribute('uv', new THREE.BufferAttribute(new Float32Array(data.uv.array), 2));
            _geometry.addAttribute('normal', new THREE.BufferAttribute(new Float32Array(data.normal.array), 3));
            _geometry.setIndex(new THREE.BufferAttribute(new Uint16Array(shape.index.array), 1));
            shape.dispose();
        }

        function initInstances() {
            var orientation = new THREE.InstancedBufferAttribute(new Float32Array(_num * 4), 4);
            var randoms = new THREE.InstancedBufferAttribute(new Float32Array(_num), 1);
            var scale = new THREE.InstancedBufferAttribute(new Float32Array(_num * 2), 2);
            var life = new THREE.InstancedBufferAttribute(new Float32Array(_num), 1);

            for (let i = 0; i < _num; i++) {
                orientation.setXYZW(i, 0, 0, 0, 1);
                life.setX(i, i / _num + 1);
            }

            _geometry.addAttribute('orientation', orientation);
            _geometry.addAttribute('scale', scale);
            _geometry.addAttribute('life', life);
            _geometry.addAttribute('random', randoms);
        }

        function initShader() {
            var uniforms = {
                uMap: {type: 't', value: null},
                uColor1: {type: 'c', value: new THREE.Color(0x961800)}, // red
                uColor2: {type: 'c', value: new THREE.Color(0x4b5828)}, // yellow
                uTime: {type: 'f', value: 0},
            };

            _shader = new THREE.ShaderMaterial({
                uniforms: uniforms,
                vertexShader: fireVertexShader,
                fragmentShader: fireFragmentShader,
                blending: THREE.AdditiveBlending,
                transparent: true,
                depthWrite: false,
            });

            var textureLoader = new THREE.TextureLoader();
            textureLoader.load('https://cinemont.com/tutorials/zelda/flame.png', t => _shader.uniforms.uMap.value = t);
        }

        function initMesh() {
            _group = new THREE.Group();
            _mesh = new THREE.Mesh(_geometry, _shader);
            _mesh.frustumCulled = false;
            _group.add(_mesh);
            _scene.add(_group);
        }

        function loop(e) {
            requestAnimationFrame(loop);
            _shader.uniforms.uTime.value = e * 0.001;

            _group.quaternion.copy(_camera.quaternion);

            var life = _geometry.attributes.life;
            var scale = _geometry.attributes.scale;
            var randoms = _geometry.attributes.random;

            for (let i = 0; i < _num; i++) {
                var value = life.array[i];
                value += 0.025;

                if (value > 1) {
                    value -= 1;

                    scale.setXY(i, random(0.8, 1.2, 3), random(0.8, 1.2, 3));
                    randoms.setX(i, random(0, 1, 3));
                }

                life.setX(i, value);
            }
            life.needsUpdate = true;
            scale.needsUpdate = true;
            randoms.needsUpdate = true;
        }
    }

    //=====// Embers //========================================//     

    function initEmbers() {
        var _geometry, _shader, _points;
        var _num = 8;

        (function() {
            initGeometry();
            initShader();
            initMesh();
            requestAnimationFrame(loop);
        })();    

        function initGeometry() {
            _geometry = new THREE.BufferGeometry();
            _geometry.addAttribute('position', new THREE.BufferAttribute(new Float32Array(_num * 3), 3));
            _geometry.addAttribute('offset', new THREE.BufferAttribute(new Float32Array(_num * 3), 3));
            _geometry.addAttribute('size', new THREE.BufferAttribute(new Float32Array(_num), 1));
            _geometry.addAttribute('life', new THREE.BufferAttribute(new Float32Array(_num), 1));

            for (let i = 0; i < _num; i++) {
                _geometry.attributes.life.setX(i, random(0, 1, 3) + 1);
            }
        }

        function initShader() {
            var uniforms = {
                uMap: {type: 't', value: null},
                uColor: {type: 'c', value: new THREE.Color(0xffe61e)},
            };

            _shader = new THREE.ShaderMaterial({
                uniforms: uniforms,
                vertexShader: embersVertexShader,
                fragmentShader: embersFragmentShader,
                blending: THREE.AdditiveBlending,
                transparent: true,
                depthTest: false,
            });

            var textureLoader = new THREE.TextureLoader();
            textureLoader.load('https://cinemont.com/tutorials/zelda/ember.png', t => _shader.uniforms.uMap.value = t);
        }

        function initMesh() {
            _points = new THREE.Points(_geometry, _shader);
            _points.frustumCulled = false;
            _scene.add(_points);
        }

        function loop() {
            requestAnimationFrame(loop);
            var life = _geometry.attributes.life;
            var position = _geometry.attributes.position;
            var size = _geometry.attributes.size;
            var offset = _geometry.attributes.offset;
            for (let i = 0; i < _num; i++) {
                var value = life.array[i];
                value += 0.02;

                if (value > 1) {
                    value -= 1;

                    offset.setXYZ(i,
                        random(-0.2, 0.2, 3),
                        random(0.7, 1.2, 3),
                        random(-0.2, 0.2, 3)
                    );
                    size.setX(i, random(0.2, 0.5, 3));
                }

                life.setX(i, value);
            }

            life.needsUpdate = true;
            position.needsUpdate = true;
            size.needsUpdate = true;
            offset.needsUpdate = true;
        }
    }

    //=====// Haze //========================================//     

    function initHaze() {
        var _geometry, _shader, _mesh;
    
        var _num = 4;
        
        var _z = new THREE.Vector3(0, 0, 1);
        var _quat = new THREE.Quaternion();
        var _quat2 = new THREE.Quaternion();

        (function() {
            initGeometry();
            initInstances();
            initShader();
            initMesh();
            window.addEventListener('resize', resizeHaze, false);
            resizeHaze();
            requestAnimationFrame(loop);
        })();    

        function initGeometry() {
            _geometry = new THREE.InstancedBufferGeometry();
            _geometry.maxInstancedCount = _num;

            var shape = new THREE.PlaneBufferGeometry(2, 2);
            var data = shape.attributes;

            _geometry.addAttribute('position', new THREE.BufferAttribute(new Float32Array(data.position.array), 3));
            _geometry.addAttribute('uv', new THREE.BufferAttribute(new Float32Array(data.uv.array), 2));
            _geometry.addAttribute('normal', new THREE.BufferAttribute(new Float32Array(data.normal.array), 3));
            _geometry.setIndex(new THREE.BufferAttribute(new Uint16Array(shape.index.array), 1));
            shape.dispose();
        }

        function initInstances() {
            var base = new THREE.InstancedBufferAttribute(new Float32Array(_num * 3), 3);
            var offset = new THREE.InstancedBufferAttribute(new Float32Array(_num * 3), 3);
            var orientation = new THREE.InstancedBufferAttribute(new Float32Array(_num * 4), 4);
            var scale = new THREE.InstancedBufferAttribute(new Float32Array(_num * 2), 2);
            var rotation = new THREE.InstancedBufferAttribute(new Float32Array(_num), 1);
            var life = new THREE.InstancedBufferAttribute(new Float32Array(_num), 1);

            for (let i = 0; i < _num; i++) {
                orientation.setXYZW(i, 0, 0, 0, 1);
                life.setX(i, i / _num + 1);
            }

            _geometry.addAttribute('base', base);
            _geometry.addAttribute('offset', offset);
            _geometry.addAttribute('orientation', orientation);
            _geometry.addAttribute('scale', scale);
            _geometry.addAttribute('rotation', rotation);
            _geometry.addAttribute('life', life);
        }

        function initShader() {
            let dpr = _renderer.getPixelRatio();
            var uniforms = {
                uMap: {type: 't', value: null},
                uMask: {type: 't', value: null},
                uResolution: {type: 'v2', value: new THREE.Vector2(_width * dpr, _height * dpr)},
            };

            _shader = new THREE.ShaderMaterial({
                uniforms: uniforms,
                vertexShader: hazeVertexShader,
                fragmentShader: hazeFragmentShader,
                transparent: true,
                depthTest: false,
            });

            var textureLoader = new THREE.TextureLoader();
            textureLoader.load('https://cinemont.com/tutorials/zelda/haze.png', t => _shader.uniforms.uMask.value = t);
        }

        function initMesh() {
            _mesh = new THREE.Mesh(_geometry, _shader);
            _mesh.frustumCulled = false;
            _scene.add(_mesh);
        }

        function resizeHaze() {
            let dpr = _renderer.getPixelRatio();
            _shader.uniforms.uMap.value = _rtt.texture;
            _shader.uniforms.uResolution.value.set(_width * dpr, _height * dpr);
        }

        function loop(e) {
            requestAnimationFrame(loop);

            _mesh.visible = false;
            _renderer.render(_scene, _camera, _rtt);
            _mesh.visible = true;

            var life = _geometry.attributes.life;
            var base = _geometry.attributes.base;
            var offset = _geometry.attributes.offset;
            var scale = _geometry.attributes.scale;
            var orientation = _geometry.attributes.orientation;
            var rotation = _geometry.attributes.rotation;
            for (let i = 0; i < _num; i++) {
                var value = life.array[i];
                value += 0.008;

                if (value > 1) {
                    value -= 1;

                    rotation.setX(i, random(0, 3.14, 3));

                    offset.setXYZ(i,
                        random(-0.2, 0.2, 3),
                        random(2.5, 3.0, 3),
                        0
                    );
                    scale.setXY(i, random(0.6, 1.2, 3), random(0.6, 1.2, 3));
                }

                _quat.copy(_camera.quaternion);
                _quat2.setFromAxisAngle(_z, rotation.array[i]);
                _quat.multiply(_quat2);
                orientation.setXYZW(i, _quat.x, _quat.y, _quat.z, _quat.w);

                life.setX(i, value);
            }

            life.needsUpdate = true;
            base.needsUpdate = true;
            scale.needsUpdate = true;
            offset.needsUpdate = true;
            orientation.needsUpdate = true;
        }
    }

})();