From fd78db348db96b6152187bed46035d05fbee8614 Mon Sep 17 00:00:00 2001
From: Francois <francoislaberge@gmail.com>
Date: Sun, 24 Sep 2023 18:09:06 -0400
Subject: [PATCH] Sorta getting there, math isn't quite right

---
 src/renderer/renderCylinder.ts     | 52 +++++++++++++++++++-----------
 workbench/scenes/SingleCylinder.ts | 26 ++-------------
 2 files changed, 37 insertions(+), 41 deletions(-)

diff --git a/src/renderer/renderCylinder.ts b/src/renderer/renderCylinder.ts
index bc2f9b6..306973c 100644
--- a/src/renderer/renderCylinder.ts
+++ b/src/renderer/renderCylinder.ts
@@ -55,21 +55,17 @@ export function renderCylinder(
   const yAxisCameraSpace = yAxisWorldSpace.clone();
   inverseCameraMatrix.extractRotation().applyToVector3(yAxisCameraSpace);
 
-  const cylinderScale = worldTransform.getScale().x;
-  const cylinderScaleFactor = cylinderScale * cameraZoom;
-  const Radius = cylinder.radius * cylinderScaleFactor;
-
   // Top === -1
   // Front === 0
   // Bottom === 1
-  const dotProduct = yAxisCameraSpace.dotProduct(
-    // cameraDirection.clone().multiply(-1)
-    Vector3(0, 0, 1)
-  );
+  const dotProduct = yAxisCameraSpace.dotProduct(Vector3(0, 0, 1)); // This boils down to just taking the z component
   const dotProductAbsolute = Math.abs(dotProduct);
+  const isTopVisible = dotProduct > 0;
 
+  const cylinderScale = worldTransform.getScale().x;
+  const cylinderScaleFactor = cylinderScale * cameraZoom;
+  const Radius = cylinder.radius * cylinderScaleFactor;
   const ShortRadius = Radius * dotProductAbsolute;
-  const isTopVisible = dotProduct > 0;
 
   console.log(
     `scenario: ${isTopVisible ? "top" : "bottom"}
@@ -164,9 +160,20 @@ export function renderCylinder(
   );
 
   addStrokeAttribute(tubePath, cylinder, cylinderScaleFactor);
-
   svg.appendChild(tubePath);
 
+  // Convert the light direction into camera space (not projected into screen space)
+  const directionalLightInCameraSpace = scene.directionalLight.direction
+    .clone()
+    .multiply(-1);
+  inverseCameraMatrix
+    .extractRotation()
+    .applyToVector3(directionalLightInCameraSpace);
+  // Then convert it into screen aligned cylinder space
+  Matrix4x4()
+    .makeRotationZ((xAxisRotation / 180) * Math.PI)
+    .applyToVector3(directionalLightInCameraSpace);
+
   const uuid = crypto.randomUUID();
   const fillUuid = uuid + "-fill";
   const fillUrl = `url(#${fillUuid})`;
@@ -198,19 +205,28 @@ export function renderCylinder(
   linearGradient.setAttribute("x2", rightOfTubeCenter.x.toString());
   linearGradient.setAttribute("y2", rightOfTubeCenter.y.toString());
 
-  const gradientStops = [
-    { offset: 0, stopColor: ColorToCSS(cylinder.fill) },
-    { offset: 1.0, stopColor: ColorToCSS(Color(0, 0, 0)) },
-  ];
+  // Add the gradient stops
+  const GradientSteps = Math.min(2, Math.max(255, Math.floor(Radius)));
+
+  for (let i = 0; i < GradientSteps; i++) {
+    const normalized = i / (GradientSteps - 1);
+    const x = Math.sin(normalized * Math.PI);
+    const z = Math.cos(normalized * Math.PI + Math.PI);
 
-  for (let stop of gradientStops) {
     const stopElement = document.createElementNS(
       "http://www.w3.org/2000/svg",
       "stop"
     );
-
-    stopElement.setAttribute("offset", stop.offset.toString());
-    stopElement.setAttribute("stop-color", stop.stopColor);
+    stopElement.setAttribute("offset", normalized.toFixed(3));
+    stopElement.setAttribute(
+      "stop-color",
+      applyLighting(
+        scene.directionalLight.color,
+        cylinder.fill,
+        scene.ambientLightColor,
+        directionalLightInCameraSpace.dotProduct(Vector3(x, 0, z))
+      )
+    );
     linearGradient.appendChild(stopElement);
   }
 
diff --git a/workbench/scenes/SingleCylinder.ts b/workbench/scenes/SingleCylinder.ts
index 6233aa8..f3cfa55 100644
--- a/workbench/scenes/SingleCylinder.ts
+++ b/workbench/scenes/SingleCylinder.ts
@@ -80,19 +80,6 @@ export default function () {
     const distanceNormalized = distance / referenceRadius;
     let degrees = distanceNormalized * 90;
 
-    //Math.cos(((distanceNormalized * 90) / 180) * Math.PI);
-    // console.log(
-    //   degrees,
-    //   event.clientX,
-    //   event.clientY,
-    //   centerX,
-    //   centerY,
-    //   diffX,
-    //   diffY,
-    //   distance,
-    //   distanceNormalized
-    // );
-
     const spinMode: string = "z";
 
     if (spinMode === "y") {
@@ -100,7 +87,6 @@ export default function () {
         degrees *= -1;
       }
       lightSphere.position.x = Math.sin((degrees / 180) * Math.PI);
-      // lightSphere.position.y = 0.0;
       lightSphere.position.y = 0.5;
       lightSphere.position.z = Math.cos((degrees / 180) * Math.PI);
 
@@ -111,17 +97,10 @@ export default function () {
     } else if (spinMode === "z") {
       lightSphere.position.x = Math.sin((degrees / 180) * Math.PI);
       lightSphere.position.y = Math.cos((degrees / 180) * Math.PI);
-      lightSphere.position.z = 0; //
-      // lightSphere.position.z = -0.5; //
+      lightSphere.position.z = 0;
     }
 
     lightSphere.position.normalize().multiply(lightDistance).add(position);
-
-    // const x = event.clientX;
-    // const z = event.clientY;
-    // lightSphere.position.y = 0;
-    // const x = event.clientX;
-    // const y = event.clientY;
   };
   document.addEventListener("pointerdown", onPointerEvent);
   document.addEventListener("pointermove", onPointerEvent);
@@ -136,7 +115,8 @@ export default function () {
 
     // cylinder.rotation.x = now * 90;
     // cylinder.rotation.x = 45;
-    cylinder.rotation.y = now * 90;
+    cylinder.rotation.x = 90;
+    // cylinder.rotation.y = now * 90;
 
     // cylinder.rotation.x = now * 90;