From cc6d3871008a89fcf48814596d7bfec05f2706e4 Mon Sep 17 00:00:00 2001
From: Matthew Kosarek <mattkae@protonmail.com>
Date: Sun, 7 Feb 2021 19:22:56 -0500
Subject: Added rotational dynamics to the examples

---
 frontend/_rigidbody/rigidbody_2.js | 77 +++++++++++++++++++++++++++++++++-----
 1 file changed, 67 insertions(+), 10 deletions(-)

(limited to 'frontend/_rigidbody/rigidbody_2.js')

diff --git a/frontend/_rigidbody/rigidbody_2.js b/frontend/_rigidbody/rigidbody_2.js
index b41fa92..c41461e 100644
--- a/frontend/_rigidbody/rigidbody_2.js
+++ b/frontend/_rigidbody/rigidbody_2.js
@@ -24,23 +24,29 @@ function main() {
         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));
+                    { 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
-                const lGravityForce = vec2(0, -1.0 * (lCircle.mass * GRAVITY));
-                lCircle.force = addVec2(lCircle.force, lGravityForce);
+                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.rotationRadians += Math.PI * pDeltaTimeSeconds;
-                lCircle.model = rotateMatrix2d(translateMatrix(mat4(), lCircle.position.x, lCircle.position.y, 0), lCircle.rotationRadians);
                 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);
@@ -55,6 +61,19 @@ function main() {
                 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);
@@ -65,14 +84,52 @@ function main() {
             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);
\ No newline at end of file
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