examples/cloth.html

<!DOCTYPE html>
<html>
<head>
    <title>PicoGL.js: Cloth</title>
    <meta charset="utf-8">
    <script src="utils/compatibility.js"></script>
    <script src="utils/gl-matrix.js"></script>
    <script src="utils/utils.js"></script>
    <link rel="stylesheet" href="../site/css/picogl-example.css"> 
</head>
<!--
  The MIT License (MIT)

  Copyright (c) 2017 Tarek Sherif

  Permission is hereby granted, free of charge, to any person obtaining a copy of
  this software and associated documentation files (the "Software"), to deal in
  the Software without restriction, including without limitation the rights to
  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
  the Software, and to permit persons to whom the Software is furnished to do so,
  subject to the following conditions:

  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-->
<!-- 
    Algorithm based on:
    - Mosegaard's Cloth Simulation Coding Tutorial (CPU implementation) 
        https://viscomp.alexandra.dk/?p=147
    - Cloth Simulation on the GPU by Cyril Zeller
        http://http.download.nvidia.com/developer/presentations/2005/SIGGRAPH/ClothSimulationOnTheGPU.pdf
 -->
<body>
    <div id="example-title">
        PicoGL.js Example: Cloth<BR>
        (Use mouse to control ball)
        <div>
            <a href="https://github.com/tsherif/picogl.js/blob/master/examples/cloth.html">Source code</a>
        </div>
    </div>
    <canvas id="gl-canvas"></canvas>
    <script id="quad-vs" type="x-shader/vs">
        #version 300 es   

        layout(location=0) in vec4 aPosition;
        
        out vec2 vScreenUV;
        void main() {
            vScreenUV = aPosition.xy * 0.5 + 0.5;
            gl_Position = aPosition;
        }
    </script>
    <script id="update-force-fs" type="x-fragment-shader">
        #version 300 es   

        precision highp float;

        #define GRAVITY vec3(0.0, -0.0003, 0.0)
        #define WIND vec3(0.0, 0.0, 0.00008)
        #define DAMPING 0.99

        in vec2 vScreenUV;

        uniform sampler2D uPositionBuffer;
        uniform sampler2D uNormalBuffer;
        uniform sampler2D uOldPositionBuffer;

        layout(location=0) out vec3 outPosition;
        layout(location=1) out vec3 outOldPosition;

        void main() {
            ivec2 dimensions = textureSize(uPositionBuffer, 0);
            ivec2 maxTexelCoord = dimensions - 1;
            ivec2 texelCoord = ivec2(vScreenUV * vec2(dimensions));
            vec3 position = texelFetch(uPositionBuffer, texelCoord, 0).xyz;
            vec3 normal = texelFetch(uNormalBuffer, texelCoord, 0).xyz;
            vec3 oldPosition = texelFetch(uOldPositionBuffer, texelCoord, 0).xyz;
            vec3 temp = position;

            if (texelCoord != ivec2(0, 0) && texelCoord != ivec2(maxTexelCoord.x, 0)) {
                position += (position - oldPosition) * DAMPING + GRAVITY;
                float wDotN = dot(WIND, normal);
                position += abs(wDotN) * sign(wDotN) * normal;
            }

            outPosition = position;
            outOldPosition = temp;
        }
    </script>
    <script id="update-constraint-fs" type="x-fragment-shader">
        #version 300 es
        
        precision highp float;

        in vec2 vScreenUV;

        // uModVal and dir used to select the direction
        // to look for the neighbour we're going to check
        layout(std140) uniform ConstraintUniforms {
            ivec2 uDir;
            int uModVal;
            float uRestDistance;   
        };

        uniform sampler2D uPositionBuffer;

        out vec3 outPosition;

        void main() {
            ivec2 dimensions = textureSize(uPositionBuffer, 0);
            ivec2 texelCoord = ivec2(vScreenUV * vec2(dimensions));
            vec3 position = texelFetch(uPositionBuffer, texelCoord, 0).xyz;

            int iDot = abs(texelCoord.x * uDir.x) + abs(texelCoord.y * uDir.y);
            int neg = iDot % 2 == uModVal ? 1 : -1;

            bool otherPin = false;

            if (texelCoord != ivec2(0, 0) && texelCoord != ivec2(dimensions.x - 1, 0)) {
                ivec2 otherCoord = texelCoord + uDir * neg;

                if (otherCoord == ivec2(0, 0) || otherCoord == ivec2(dimensions.x - 1, 0)) {
                    otherPin = true;
                }

                if (all(greaterThanEqual(otherCoord, ivec2(0, 0))) && all(lessThan(otherCoord, dimensions))) {
                    vec3 otherPosition = texelFetch(uPositionBuffer, otherCoord, 0).xyz;
                    
                    vec3 diffVec = otherPosition - position;
                    float dist = length(diffVec);
                    if (dist > uRestDistance) {
                        position += diffVec * (1.0 - uRestDistance / dist) * (otherPin ? 1.0 : 0.5);
                    }
                }
            }

            outPosition = position;
        }
    </script>
    <script id="update-collision-fs" type="x-fragment-shader">
        #version 300 es
        
        precision highp float;

        in vec2 vScreenUV;

        layout(std140) uniform BallUniforms {
            vec4 position;
            float radius;
        } ball;

        uniform sampler2D uPositionBuffer;

        out vec3 outPosition;

        void main() {
            vec2 dimensions = vec2(textureSize(uPositionBuffer, 0));
            ivec2 texelCoord = ivec2(vScreenUV * dimensions);
            vec3 position = texelFetch(uPositionBuffer, texelCoord, 0).xyz;

            vec3 diff = position - ball.position.xyz;
            float dist = length(diff);
            if (dist < ball.radius + 0.01) {
                position += (ball.radius + 0.01 - dist) * normalize(diff);
            }

            outPosition = position;
        }
    </script>

    <script id="update-normal-fs" type="x-fragment-shader">
        #version 300 es
        
        precision highp float;

        in vec2 vScreenUV;

        uniform sampler2D uPositionBuffer;

        out vec3 outNormal;

        void main() {
            ivec2 dimensions = textureSize(uPositionBuffer, 0);
            ivec2 texelCoord = ivec2(vScreenUV * vec2(dimensions));
            vec3 position = texelFetch(uPositionBuffer, texelCoord, 0).xyz;

            vec3 normal = vec3(0.0);

            if (texelCoord.x > 0) {
                vec3 left = texelFetch(uPositionBuffer, texelCoord - ivec2(1, 0), 0).xyz;

                if (texelCoord.y > 0) {
                    vec3 down = texelFetch(uPositionBuffer, texelCoord - ivec2(0, 1), 0).xyz;
                    normal += normalize(cross(left - position, down - position));
                }

                if (texelCoord.y < dimensions.y - 1) {
                    vec3 up = texelFetch(uPositionBuffer, texelCoord + ivec2(0, 1), 0).xyz;
                    normal += normalize(cross(up - position, left - position));
                }
            }

            if (texelCoord.x < dimensions.x - 1) {
                vec3 right = texelFetch(uPositionBuffer, texelCoord + ivec2(1, 0), 0).xyz;

                if (texelCoord.y > 0) {
                    vec3 down = texelFetch(uPositionBuffer, texelCoord - ivec2(0, 1), 0).xyz;
                    normal += normalize(cross(down - position, right - position));
                }

                if (texelCoord.y < dimensions.y - 1) {
                    vec3 up = texelFetch(uPositionBuffer, texelCoord + ivec2(0, 1), 0).xyz;
                    normal += normalize(cross(right - position, up - position));
                }
            }

            outNormal = normalize(normal);
        }
    </script>
    
    <script id="ball-vs" type="x-vertex-shader">
        #version 300 es

        layout(location=0) in vec3 aPosition;
        layout(location=1) in vec3 aNormal;

        layout(std140) uniform; 

        uniform BallUniforms {
            vec4 position;
            float radius;
        } ball;

        uniform SceneUniforms {
            mat4 viewProj;
            vec4 lightPosition;
        };

        out vec3 vPosition;
        out vec2 vUV;
        out vec3 vNormal;

        void main() {
            vPosition = aPosition + ball.position.xyz;
            vUV = vec2(0.0, 0.0);
            vNormal = aNormal;

            gl_Position = viewProj * vec4(vPosition, 1.0);
        }

    </script>
    <script id="cloth-vs" type="x-vertex-shader">
        #version 300 es   
       
        layout(location=0) in ivec2 aTexelCoord;
        layout(location=1) in vec2 aUV;
 
        uniform sampler2D uPositionBuffer;
        uniform sampler2D uNormalBuffer;

        layout(std140, column_major) uniform  SceneUniforms {
            mat4 viewProj;
            vec4 lightPosition;
        };

        out vec3 vPosition;
        out vec2 vUV;
        out vec3 vNormal;
        
        void main() {
            vec3 position = texelFetch(uPositionBuffer, aTexelCoord, 0).xyz;

            vPosition = position;
            vNormal = texelFetch(uNormalBuffer, aTexelCoord, 0).xyz;
            vUV = aUV;
            gl_PointSize = 4.0;
            gl_Position = viewProj * vec4(position, 1.0);
        }
    </script>
    <script id="phong-fs" type="x-fragment-shader">
        #version 300 es
        precision highp float;

        layout(std140, column_major) uniform SceneUniforms {
            mat4 viewProj;
            vec4 lightPosition;
        };

        uniform sampler2D uDiffuse;
        
        in vec3 vPosition;
        in vec2 vUV;
        in vec3 vNormal;

        out vec4 fragColor;
        void main() {
            vec3 color = texture(uDiffuse, vUV).rgb;

            vec3 normal = normalize(vNormal);
            vec3 lightVec = -normalize(vPosition - lightPosition.xyz);
            float diffuse = abs(dot(lightVec, normal));
            float ambient = 0.1;
            fragColor = vec4(color * (diffuse + ambient), 1.0);
        }
    </script>
    <script type="module">
        import { PicoGL } from "../src/picogl.js";
       
        utils.addTimerElement();
        utils.instrumentAnimationFrame();

        if (!testExtension("EXT_color_buffer_float")) {
            document.body.innerHTML = "This example requires extension <b>EXT_color_buffer_float</b> which is not supported on this system."
        }
        
        let canvas = document.getElementById("gl-canvas");
        canvas.width = window.innerWidth;
        canvas.height = window.innerHeight;
        
        let app = PicoGL.createApp(canvas)
        .clearColor(0.0, 0.0, 0.0, 1.0)
        .enable(PicoGL.DEPTH_TEST);

        let timer = app.createTimer();

        const CONSTRAINT_ITERATIONS = 20;
        const DATA_TEXTURE_DIM = 60;
        const NUM_PARTICLES = DATA_TEXTURE_DIM * DATA_TEXTURE_DIM;
        const STRUCTURAL_REST = 1 / DATA_TEXTURE_DIM;
        const SHEAR_REST = Math.sqrt(2 * STRUCTURAL_REST * STRUCTURAL_REST);
        const BALL_RADIUS = 0.15;
        const BALL_RANGE = 0.9;
        let ballSpeed = 0.004;    

        ///////////////////
        // PROGRAMS
        ///////////////////

        // Generic quad vertex shader
        let quadVsSource = document.getElementById("quad-vs").text;
        let quadShader = app.createShader(PicoGL.VERTEX_SHADER, quadVsSource);

        // Update wind and gravity forces
        let updateForceFsSource = document.getElementById("update-force-fs").text;

        // Apply structural and shear constraints
        let updateConstraintFsSource = document.getElementById("update-constraint-fs").text;

        // Check for collision with ball
        let updateCollisionFsSource = document.getElementById("update-collision-fs").text;
        // Calculate normals
        let updateNormalFsSource = document.getElementById("update-normal-fs").text;
        

        // Generic phong shader used for drawing
        let phongSource = document.getElementById("phong-fs").text;
        let phongShader = app.createShader(PicoGL.FRAGMENT_SHADER, phongSource);

        // Draw ball
        let ballVsSource = document.getElementById("ball-vs").text;

        // Draw cloth
        let clothVsSource = document.getElementById("cloth-vs").text;

        ////////////////////
        // FRAME BUFFERS
        ////////////////////

        // Store results of force update
        let forceTarget1 = app.createTexture2D(DATA_TEXTURE_DIM, DATA_TEXTURE_DIM, { 
            internalFormat: PicoGL.RGBA32F
        });
        let forceTarget2 = app.createTexture2D(DATA_TEXTURE_DIM, DATA_TEXTURE_DIM, { 
            internalFormat: PicoGL.RGBA32F
        });

        let updateForceFramebuffer = app.createFramebuffer(DATA_TEXTURE_DIM, DATA_TEXTURE_DIM)
        .colorTarget(0, forceTarget1)
        .colorTarget(1, forceTarget2);

        // Results of constraint satisfaction passes
        let updateTarget = app.createTexture2D(DATA_TEXTURE_DIM, DATA_TEXTURE_DIM, { 
            internalFormat: PicoGL.RGBA32F
        });

        let updateFramebuffer = app.createFramebuffer(DATA_TEXTURE_DIM, DATA_TEXTURE_DIM)
        .colorTarget(0, updateTarget);

        ///////////////////////////
        // CLOTH GEOMETRY DATA
        ///////////////////////////

        let clothPositionData = new Float32Array(NUM_PARTICLES * 4);
        let clothNormalData = new Float32Array(NUM_PARTICLES * 4);
        let uvData = new Float32Array(NUM_PARTICLES * 2);
        let dataTextureIndex = new Int16Array(NUM_PARTICLES * 2);
        let indexData = new Uint16Array((DATA_TEXTURE_DIM - 1) * (DATA_TEXTURE_DIM - 1) * 6);

        let indexI = 0;
        for (let i = 0; i < NUM_PARTICLES; ++i) {
            let vec4i = i * 4;
            let vec2i = i * 2;

            let x = (i % DATA_TEXTURE_DIM);
            let y = Math.floor(i / DATA_TEXTURE_DIM);

            let u = x / DATA_TEXTURE_DIM;
            let v = y / DATA_TEXTURE_DIM;

            clothPositionData[vec4i] = u - 0.5;
            clothPositionData[vec4i + 1] = v + 0.8;

            clothNormalData[vec4i + 2] = 1;

            uvData[vec2i] = u;
            uvData[vec2i + 1] = v;

            dataTextureIndex[vec2i] = (i % DATA_TEXTURE_DIM);
            dataTextureIndex[vec2i + 1] = Math.floor(i / DATA_TEXTURE_DIM);

            if (x < DATA_TEXTURE_DIM - 1 && y < DATA_TEXTURE_DIM - 1) {
                indexData[indexI]     = i;
                indexData[indexI + 1] = i + DATA_TEXTURE_DIM;
                indexData[indexI + 2] = i + DATA_TEXTURE_DIM + 1;
                indexData[indexI + 3] = i;
                indexData[indexI + 4] = i + DATA_TEXTURE_DIM + 1;
                indexData[indexI + 5] = i + 1;
                indexI += 6;
            }
        }

        ///////////////////////////
        // SIM DATA TEXTURES
        ///////////////////////////

        let positionTextureA = app.createTexture2D(clothPositionData, DATA_TEXTURE_DIM, DATA_TEXTURE_DIM, {
            internalFormat: PicoGL.RGBA32F,
            minFilter: PicoGL.NEAREST,
            magFilter: PicoGL.NEAREST,
            wrapS: PicoGL.CLAMP_TO_EDGE,
            wrapT: PicoGL.CLAMP_TO_EDGE
        });

        let oldPositionTextureA = app.createTexture2D(clothPositionData, DATA_TEXTURE_DIM, DATA_TEXTURE_DIM, {
            internalFormat: PicoGL.RGBA32F,
            minFilter: PicoGL.NEAREST,
            magFilter: PicoGL.NEAREST,
            wrapS: PicoGL.CLAMP_TO_EDGE,
            wrapT: PicoGL.CLAMP_TO_EDGE
        });

        let positionTextureB = updateForceFramebuffer.colorAttachments[0];
        let oldPositionTextureB = updateForceFramebuffer.colorAttachments[1];

        let normalTexture = app.createTexture2D(clothNormalData, DATA_TEXTURE_DIM, DATA_TEXTURE_DIM, {
            internalFormat: PicoGL.RGBA32F,
            minFilter: PicoGL.NEAREST,
            magFilter: PicoGL.NEAREST,
            wrapS: PicoGL.CLAMP_TO_EDGE,
            wrapT: PicoGL.CLAMP_TO_EDGE
        });

        /////////////////////////
        // GEOMETRY FOR DRAWING
        /////////////////////////
        
        // Quad for simulation passes
        let quadPositions = app.createVertexBuffer(PicoGL.FLOAT, 2, new Float32Array([
            -1, 1,
            -1, -1,
            1, -1,
            -1, 1,
            1, -1,
            1, 1,
        ]));

        let quadArray = app.createVertexArray()
        .vertexAttributeBuffer(0, quadPositions);

        // Cloth geometry for drawing
        let dataIndex = app.createVertexBuffer(PicoGL.SHORT, 2, dataTextureIndex);
        let uv = app.createVertexBuffer(PicoGL.FLOAT, 2, uvData);
        let indices = app.createIndexBuffer(PicoGL.UNSIGNED_SHORT, indexData);

        let clothArray = app.createVertexArray()
        .vertexAttributeBuffer(0, dataIndex)
        .vertexAttributeBuffer(1, uv)
        .indexBuffer(indices);

        // Ball geometry
        let ballGeo = utils.createSphere({radius: BALL_RADIUS});
        let ballPositions = app.createVertexBuffer(PicoGL.FLOAT, 3, ballGeo.positions);
        let ballNormals = app.createVertexBuffer(PicoGL.FLOAT, 3, ballGeo.normals);
        let ballIndices = app.createIndexBuffer(PicoGL.UNSIGNED_SHORT, ballGeo.indices);

        let ballArray = app.createVertexArray()
        .vertexAttributeBuffer(0, ballPositions)
        .vertexAttributeBuffer(1, ballNormals)
        .indexBuffer(ballIndices);


        ////////////////
        // UNIFORMS
        ////////////////

        // Constraint uniforms
        let updateHorizontal1Uniforms = app.createUniformBuffer([
            PicoGL.INT_VEC2,
            PicoGL.INT,
            PicoGL.FLOAT
        ])
        .set(0, new Int32Array([1, 0]))
        .set(1, 0)
        .set(2, STRUCTURAL_REST)
        .update();

        let updateHorizontal2Uniforms = app.createUniformBuffer([
            PicoGL.INT_VEC2,
            PicoGL.INT,
            PicoGL.FLOAT
        ])
        .set(0, new Int32Array([1, 0]))
        .set(1, 1)
        .set(2, STRUCTURAL_REST)
        .update();

        let updateVertical1Uniforms = app.createUniformBuffer([
            PicoGL.INT_VEC2,
            PicoGL.INT,
            PicoGL.FLOAT
        ])
        .set(0, new Int32Array([0, 1]))
        .set(1, 0)
        .set(2, STRUCTURAL_REST)
        .update();

        let updateVertical2Uniforms = app.createUniformBuffer([
            PicoGL.INT_VEC2,
            PicoGL.INT,
            PicoGL.FLOAT
        ])
        .set(0, new Int32Array([0, 1]))
        .set(1, 1)
        .set(2, STRUCTURAL_REST)
        .update();

        let updateShear1Uniforms = app.createUniformBuffer([
            PicoGL.INT_VEC2,
            PicoGL.INT,
            PicoGL.FLOAT
        ])
        .set(0, new Int32Array([1, 1]))
        .set(1, 0)
        .set(2, SHEAR_REST)
        .update();

        let updateShear2Uniforms = app.createUniformBuffer([
            PicoGL.INT_VEC2,
            PicoGL.INT,
            PicoGL.FLOAT
        ])
        .set(0, new Int32Array([1, 1]))
        .set(1, 1)
        .set(2, SHEAR_REST)
        .update();

        let updateShear3Uniforms = app.createUniformBuffer([
            PicoGL.INT_VEC2,
            PicoGL.INT,
            PicoGL.FLOAT
        ])
        .set(0, new Int32Array([1, -1]))
        .set(1, 0)
        .set(2, SHEAR_REST)
        .update();

        let updateShear4Uniforms = app.createUniformBuffer([
            PicoGL.INT_VEC2,
            PicoGL.INT,
            PicoGL.FLOAT
        ])
        .set(0, new Int32Array([1, -1]))
        .set(1, 1)
        .set(2, SHEAR_REST)
        .update();

        // Draw uniforms
        let ballPosition = vec3.fromValues(0, 0.15, -0.8);
        let ballUniforms = app.createUniformBuffer([
            PicoGL.FLOAT_VEC4,
            PicoGL.FLOAT
        ])
        .set(0, ballPosition)
        .set(1, BALL_RADIUS)
        .update();
        
        let ballColor = new Uint8Array([255, 20, 20]);
        let ballTexture = app.createTexture2D(ballColor, 1, 1, { internalFormat: PicoGL.RGB8 });

        let projMatrix = mat4.create();
        mat4.perspective(projMatrix, Math.PI / 2, canvas.width / canvas.height, 0.1, 3.0);

        let viewMatrix = mat4.create();
        let eyePosition = vec3.fromValues(0.5, 0.7, 1.2);
        mat4.lookAt(viewMatrix, eyePosition, vec3.fromValues(0, 0.1, 0), vec3.fromValues(0, 1, 0));

        let viewProjMatrix = mat4.create();
        mat4.multiply(viewProjMatrix, projMatrix, viewMatrix);

        let lightPosition = vec3.fromValues(1, 1, 1);

        let sceneUniformBuffer = app.createUniformBuffer([
            PicoGL.FLOAT_MAT4,
            PicoGL.FLOAT_VEC4
        ])
        .set(0, viewProjMatrix)
        .set(1, lightPosition)
        .update();

        window.onresize = function() {
            app.resize(window.innerWidth, window.innerHeight);

            mat4.perspective(projMatrix, Math.PI / 2, app.width / app.height, 0.1, 3.0);
            mat4.multiply(viewProjMatrix, projMatrix, viewMatrix);
            
            sceneUniformBuffer.set(0, viewProjMatrix).update();
        };


        let targetZ = null;
        let targetY = null;
        canvas.addEventListener("mousemove", function(event) {
            targetZ = -((event.clientX / canvas.width) * 2 - 1);
            targetY = ((canvas.height - event.clientY) / canvas.height) * 2 - 1;
        });

        Promise.all([
            app.createPrograms(
                [quadShader, updateForceFsSource],
                [quadShader, updateConstraintFsSource],
                [quadShader, updateCollisionFsSource],
                [quadShader, updateNormalFsSource],
                [ballVsSource, phongShader],
                [clothVsSource, phongShader]
            ),
            utils.loadImages(["img/webgl-logo.png"])
        ]).then(([
            [updateForceProgram, updateConstraintProgram, updateCollisionProgram, updateNormalProgram, ballProgram, clothProgram],
            [image]
        ]) => {
            let texture = app.createTexture2D(image, { 
                maxAnisotropy: PicoGL.WEBGL_INFO.MAX_TEXTURE_ANISOTROPY 
            });
            
            ///////////////
            // DRAW CALLS
            ///////////////

            // Update forces
            let updateForceDrawCall = app.createDrawCall(updateForceProgram, quadArray)
            .texture("uPositionBuffer", positionTextureA)
            .texture("uNormalBuffer", normalTexture);

            // Structural constraints
            let updateHorizontal1DrawCall = app.createDrawCall(updateConstraintProgram, quadArray)
            .uniformBlock("ConstraintUniforms", updateHorizontal1Uniforms);

            let updateHorizontal2DrawCall  = app.createDrawCall(updateConstraintProgram, quadArray)
            .uniformBlock("ConstraintUniforms", updateHorizontal2Uniforms);

            let updateVertical1DrawCall = app.createDrawCall(updateConstraintProgram, quadArray)
            .uniformBlock("ConstraintUniforms", updateVertical1Uniforms);

            let updateVertical2DrawCall = app.createDrawCall(updateConstraintProgram, quadArray)
            .uniformBlock("ConstraintUniforms", updateVertical2Uniforms);

            // Shear constraints
            let updateShear1DrawCall = app.createDrawCall(updateConstraintProgram, quadArray)
            .uniformBlock("ConstraintUniforms", updateShear1Uniforms);

            let updateShear2DrawCall = app.createDrawCall(updateConstraintProgram, quadArray)
            .uniformBlock("ConstraintUniforms", updateShear2Uniforms);

            let updateShear3DrawCall = app.createDrawCall(updateConstraintProgram, quadArray)
            .uniformBlock("ConstraintUniforms", updateShear3Uniforms);

            let updateShear4DrawCall = app.createDrawCall(updateConstraintProgram, quadArray)
            .uniformBlock("ConstraintUniforms", updateShear4Uniforms);

            let updateCollisionDrawCall = app.createDrawCall(updateCollisionProgram, quadArray)
            .uniformBlock("BallUniforms", ballUniforms);

            let updateNormalDrawCall = app.createDrawCall(updateNormalProgram, quadArray);

            let clothDrawCall = app.createDrawCall(clothProgram, clothArray)
            .uniformBlock("SceneUniforms", sceneUniformBuffer)
            .texture("uDiffuse", texture)
            .texture("uNormalBuffer", normalTexture);
            
            let ballDrawCall = app.createDrawCall(ballProgram, ballArray)
            .uniformBlock("SceneUniforms", sceneUniformBuffer)
            .uniformBlock("BallUniforms", ballUniforms)
            .texture("uDiffuse", ballTexture);

            /////////
            // DRAW
            /////////

            function draw() {
                if (timer.ready()) {
                    utils.updateTimerElement(timer.cpuTime, timer.gpuTime);
                }

                timer.start();

                updateForceDrawCall.texture("uPositionBuffer", positionTextureA);
                updateForceDrawCall.texture("uOldPositionBuffer", oldPositionTextureA);
                updateForceFramebuffer.colorTarget(0, positionTextureB);
                updateForceFramebuffer.colorTarget(1, oldPositionTextureB);

                app.viewport(0, 0, DATA_TEXTURE_DIM, DATA_TEXTURE_DIM);

                app.drawFramebuffer(updateForceFramebuffer);
                updateForceDrawCall.draw();

                for (let i = 0; i < CONSTRAINT_ITERATIONS; ++i) {
                    app.drawFramebuffer(updateFramebuffer);

                    updateFramebuffer.colorTarget(0, positionTextureA);
                    updateHorizontal1DrawCall.texture("uPositionBuffer", positionTextureB).draw();

                    updateFramebuffer.colorTarget(0, positionTextureB);
                    updateHorizontal2DrawCall.texture("uPositionBuffer", positionTextureA).draw();

                    updateFramebuffer.colorTarget(0, positionTextureA);
                    updateVertical1DrawCall.texture("uPositionBuffer", positionTextureB).draw();

                    updateFramebuffer.colorTarget(0, positionTextureB);
                    updateVertical2DrawCall.texture("uPositionBuffer", positionTextureA).draw();

                    updateFramebuffer.colorTarget(0, positionTextureA);
                    updateShear1DrawCall.texture("uPositionBuffer", positionTextureB).draw();

                    updateFramebuffer.colorTarget(0, positionTextureB);
                    updateShear2DrawCall.texture("uPositionBuffer", positionTextureA).draw();

                    updateFramebuffer.colorTarget(0, positionTextureA);
                    updateShear3DrawCall.texture("uPositionBuffer", positionTextureB).draw();

                    updateFramebuffer.colorTarget(0, positionTextureB);
                    updateShear4DrawCall.texture("uPositionBuffer", positionTextureA).draw();   
                }

                if (targetZ === null) {
                    ballPosition[2] += ballSpeed;

                    if (ballPosition[2] > BALL_RANGE || ballPosition[2] < -BALL_RANGE) {
                        ballSpeed *= -1;
                    }

                    ballUniforms.set(0, ballPosition).update();
                } else {
                    let zDiff = targetZ - ballPosition[2];
                    let yDiff = targetY - ballPosition[1];

                    if (Math.abs(zDiff) > 0.001 || Math.abs(yDiff) > 0.001) {
                        ballPosition[2] += zDiff * 0.02;
                        ballPosition[1] += yDiff * 0.02;
                        ballUniforms.set(0, ballPosition).update();
                    }
                }

                updateFramebuffer.colorTarget(0, positionTextureA);
                updateCollisionDrawCall.texture("uPositionBuffer", positionTextureB).draw();

                updateFramebuffer.colorTarget(0, normalTexture);
                updateNormalDrawCall.texture("uPositionBuffer", positionTextureA).draw();

                clothDrawCall.texture("uPositionBuffer", positionTextureA);

                app.defaultViewport().defaultDrawFramebuffer().clear();
                clothDrawCall.draw();
                ballDrawCall.draw();

                let temp = oldPositionTextureA;
                oldPositionTextureA = oldPositionTextureB;
                oldPositionTextureB = temp;


                timer.end();

                requestAnimationFrame(draw);
            }

            requestAnimationFrame(draw); 
        });

    </script>
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