From 376e1a7f9207fffb1ec3027ac1e7f32db5de4922 Mon Sep 17 00:00:00 2001
From: Matthew Kosarek <mattkae@protonmail.com>
Date: Sat, 6 Feb 2021 18:39:48 -0500
Subject: Initial commit

---
 frontend/_rigidbody/circle.js | 58 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 frontend/_rigidbody/circle.js

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

diff --git a/frontend/_rigidbody/circle.js b/frontend/_rigidbody/circle.js
new file mode 100644
index 0000000..c044597
--- /dev/null
+++ b/frontend/_rigidbody/circle.js
@@ -0,0 +1,58 @@
+const BYTES_PER_FLOAT = 4;
+
+function circle(pGl, pRadius, pSegments, pColorList, pInitialPosition) {
+    const lBuffer = pGl.createBuffer();
+
+    pGl.bindBuffer(pGl.ARRAY_BUFFER, lBuffer);
+
+    var lBufferedData = [];
+    vertexCount = 0;
+
+    const lAngleIncrements = (360.0 / pSegments) * (Math.PI / 180.0);
+    for (let lSegIdx = 0; lSegIdx < pSegments; lSegIdx++) {
+        const lAngle = lAngleIncrements * lSegIdx,
+            lNextAngle = lAngleIncrements * (lSegIdx + 1),
+            lColorIndex = Math.floor(pColorList.length * (lSegIdx / pSegments)),
+            lColor = pColorList[lColorIndex]; // TODO: Calculate which one to use
+
+        lBufferedData = lBufferedData.concat([
+            0,                              0,                              lColor.x, lColor.y, lColor.z, lColor.w,
+            pRadius * Math.sin(lAngle),     pRadius * Math.cos(lAngle),     lColor.x, lColor.y, lColor.z, lColor.w,
+            pRadius * Math.sin(lNextAngle), pRadius * Math.cos(lNextAngle), lColor.x, lColor.y, lColor.z, lColor.w
+        ]);
+
+        vertexCount += 3;
+    }
+
+    pGl.bufferData(pGl.ARRAY_BUFFER, new Float32Array(lBufferedData), pGl.STATIC_DRAW)
+    pGl.bindBuffer(pGl.ARRAY_BUFFER, undefined);
+
+    return { 
+        buffer: lBuffer, 
+        vertexCount: vertexCount,
+        position: pInitialPosition || vec2(),
+        velocity: vec2(),
+        force: vec2(),
+        mass: 1,
+        rotationRadians: 0,
+        model: mat4(),
+        radius: pRadius
+    };
+}
+
+function renderCircle(pGl, pProgramInfo, pCircle) {
+    pGl.bindBuffer(pGl.ARRAY_BUFFER, pCircle.buffer);
+    {
+        pGl.enableVertexAttribArray(pProgramInfo.attributeLocations.position);
+        pGl.vertexAttribPointer(pProgramInfo.attributeLocations.position, 2, pGl.FLOAT, false, BYTES_PER_FLOAT * 6, 0);
+
+        pGl.enableVertexAttribArray(pProgramInfo.attributeLocations.color);
+        pGl.vertexAttribPointer(pProgramInfo.attributeLocations.color, 4, pGl.FLOAT, false, BYTES_PER_FLOAT * 6, BYTES_PER_FLOAT * 2);
+    }
+
+    pGl.drawArrays(pGl.TRIANGLE_STRIP, 0, pCircle.vertexCount);
+}
+
+function getMomentOfInertia(pCircle) {
+    return (Math.PI * Math.pow(pCircle.radius, 4)) / 4;
+}
\ No newline at end of file
-- 
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