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path: root/frontend/_rigidbody/rigidbody_2.js
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/// <reference path="../scripts/jquery-3.5.1.min.js"/>
/// <reference path="vec2.js" />
/// <reference path="mat4.js" />
/// <reference path="shader.js" />
/// <reference path="circle.js" />

function main() {
    // Define Constants
    const CIRCLE_RADIUS = 16;
    const GRAVITY = 9.8;

    // Retrieve context
    const lProgramContext = getContext('#rigidbody_2');

    if (lProgramContext.gl === null) {
        console.error('Unable to initialize WebGL. Your browser or machine may not support it.');
        return;
    }

    lProgramContext.gl.clearColor(0.0, 0.0, 0.0, 1.0);
    lProgramContext.gl.clear(lProgramContext.gl.COLOR_BUFFER_BIT);

    function run() {
        console.log('Running Rigid Body 2');
        lProgramContext.load().then(function(pProgramInfo) {
            const lCircle = circle(lProgramContext.gl, CIRCLE_RADIUS, 30, [
                    { x: 1, y: 1, z: 0, w: 1 },
                    { x: 1, y: 0, z: 1, w: 1 },
                    { x: 0, y: 1, z: 1, w: 1 },
                    { x: 0, y: 1, z: 0, w: 1 }
                ], vec2(lProgramContext.width / 2.0, lProgramContext.height / 2.0));

            function update(pDeltaTimeSeconds) {
                // Same physics updates from previously
                applyForce(vec2(0, -1.0 * (lCircle.mass * GRAVITY)));
                const lCurrentAcceleration = scaleVec2(lCircle.force, 1.0 / lCircle.mass);
                lCircle.velocity = addVec2(lCircle.velocity, scaleVec2(lCurrentAcceleration, pDeltaTimeSeconds));
                lCircle.position = addVec2(lCircle.position, scaleVec2(lCircle.velocity, pDeltaTimeSeconds));
                lCircle.force = vec2();

                // Calculate rotation
                const lMomentOfInertia = getMomentOfInertia(lCircle);
                const lAngularAcceleration = lCircle.torque / lMomentOfInertia;

                lCircle.rotationVelocity += lAngularAcceleration * pDeltaTimeSeconds;
                lCircle.rotationRadians += lCircle.rotationVelocity * pDeltaTimeSeconds;
                lCircle.model = rotateMatrix2d(translateMatrix(mat4(), lCircle.position.x, lCircle.position.y, 0), lCircle.rotationRadians);
                lCircle.torque = 0;

                // Render Code only
                lProgramContext.gl.clearColor(0.0, 0.0, 0.0, 1.0);
                lProgramContext.gl.clearDepth(1.0);
                lProgramContext.gl.enable(lProgramContext.gl.DEPTH_TEST);
                lProgramContext.gl.depthFunc(lProgramContext.gl.LEQUAL);
                lProgramContext.gl.clear(lProgramContext.gl.COLOR_BUFFER_BIT | lProgramContext.gl.DEPTH_BUFFER_BIT);

                lProgramContext.gl.useProgram(pProgramInfo.program);
                lProgramContext.gl.uniformMatrix4fv(pProgramInfo.uniformLocations.projection, false, lProgramContext.perspective);
                lProgramContext.gl.uniformMatrix4fv(pProgramInfo.uniformLocations.model, false, lCircle.model);

                renderCircle(lProgramContext.gl, pProgramInfo, lCircle);
            }

            const TORQUE_MULTIPLIER = 100.0; // TODO: This may be unncessary

            function applyForce(pForceVector, pPointOfApplication) {
                if (pPointOfApplication !== undefined) {
                    const lOriginToPointOfApp = subVec2(vec2(), pPointOfApplication), // The point of application is relative to the model (i.e. the center of the circle, not the scene)
                        lPerpVec = vec2(-lOriginToPointOfApp.y, lOriginToPointOfApp.x);
    
                    lCircle.torque += TORQUE_MULTIPLIER * dot2(lPerpVec, pForceVector);
                }

                lCircle.force = addVec2(lCircle.force, pForceVector);
            }

            function cleanup() {
                lProgramContext.gl.deleteBuffer(lCircle.buffer);
                lProgramContext.gl.deleteProgram(pProgramInfo.program);
                lProgramContext.gl.clearColor(0.0, 0.0, 0.0, 1.0);
                lProgramContext.gl.clear(lProgramContext.gl.COLOR_BUFFER_BIT);
            }

            function reset() {
                lExitRequestFunc();
                lProgramContext.reset();
                $('#rigidbody_2_force_submit_button').unbind('submit').submit(false);
            }

            const lExitRequestFunc = requestUpdateLoop(update, cleanup);
            lProgramContext.stopButton.on('click', reset);
            $('#rigidbody_2_force_submit_button').submit(function(pEv) {
                pEv.preventDefault();
                pEv.stopPropagation();

                // Read in the force vector from the form
                const lForceGroup = $('#rigidbody_2_force_input'),
                    lPositionGroup = $('#rigidbody_2_position_input');

                let lForceVectorX = lForceGroup.find('.vec2_x_input').val(),
                    lForceVectorY = lForceGroup.find('.vec2_y_input').val();

                if (lForceVectorX.length === 0) {
                    lForceVectorX = 0;
                }

                if (lForceVectorY.length === 0) {
                    lForceVectorY = 5000;
                }

                // Read in the point of application vector from the form
                let lPositionGroupX = lPositionGroup.find('.vec2_x_input').val(),
                    lPositionGroupY = lPositionGroup.find('.vec2_y_input').val();

                if (lPositionGroupX.length === 0) {
                    lPositionGroupX = -Math.sqrt(2) / 2;
                }

                if (lPositionGroupY.length === 0) {
                    lPositionGroupY = -Math.sqrt(2) / 2;
                }

                const lForceVector = vec2(Number(lForceVectorX), Number(lForceVectorY));
                const lPointOfApplication = scaleVec2(normalize2(vec2(Number(lPositionGroupX), Number(lPositionGroupY))), lCircle.radius);

                applyForce(lForceVector, lPointOfApplication);
            });
        });
    }
    
    lProgramContext.playButton.on('click', run);
    $('#rigidbody_2_force_submit_button').submit(false);
}

$(document).ready(main);