From a37b66bb5ec18ed7b088c9bb191a004825b3aafc Mon Sep 17 00:00:00 2001
From: Szymon Nowakowski <smnbdg13@gmail.com>
Date: Fri, 4 Aug 2023 21:45:10 +0200
Subject: [PATCH] Computing normal matrix

---
 src/data/Matrix4x4.ts | 34 ++++++++++++++++++++++++++++++++++
 src/oktaeder.ts       | 19 +++++++++++++++++--
 2 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/src/data/Matrix4x4.ts b/src/data/Matrix4x4.ts
index bbcbe80..546e11a 100644
--- a/src/data/Matrix4x4.ts
+++ b/src/data/Matrix4x4.ts
@@ -506,6 +506,40 @@ export class Matrix4x4 {
 		this.tw = tw;
 		return this;
 	}
+
+	inverseTransposeAffine(): Matrix4x4 {
+		const ix = this.ix;
+		const iy = this.iy;
+		const iz = this.iz;
+		const jx = this.jx;
+		const jy = this.jy;
+		const jz = this.jz;
+		const kx = this.kx;
+		const ky = this.ky;
+		const kz = this.kz;
+		const tx = this.tx;
+		const ty = this.ty;
+		const tz = this.tz;
+
+		const det = ix * jy * kz + iy * jz * kx + iz * jx * ky
+			- ix * jz * ky - iy * jx * kz - iz * jy * kx;
+		const invDet = 1 / det;
+
+		this.ix = invDet * (jy * kz - jz * ky);
+		this.iy = invDet * (jz * kx - jx * kz);
+		this.iz = invDet * (jx * ky - jy * kx);
+		this.jx = invDet * (iz * ky - iy * kz);
+		this.jy = invDet * (ix * kz - iz * kx);
+		this.jz = invDet * (iy * kx - ix * ky);
+		this.kx = invDet * (iy * jz - iz * jy);
+		this.ky = invDet * (iz * jx - ix * jz);
+		this.kz = invDet * (ix * jy - iy * jx);
+		this.tx = -(this.ix * tx + this.iy * ty + this.iz * tz);
+		this.ty = -(this.jx * tx + this.jy * ty + this.jz * tz);
+		this.tz = -(this.kx * tx + this.ky * ty + this.kz * tz);
+
+		return this;
+	}
 }
 
 Object.defineProperty(Matrix4x4.prototype, "type", { value: "Matrix4x4" });
diff --git a/src/oktaeder.ts b/src/oktaeder.ts
index 1a9d0c9..ad7f2ec 100644
--- a/src/oktaeder.ts
+++ b/src/oktaeder.ts
@@ -9,10 +9,17 @@ export * from "./shader";
 
 import { _BinaryWriter as BinaryWriter } from "./_BinaryWriter";
 import { _Mapping as Mapping } from "./_Mapping";
-import { Camera, Material, Node, Scene, preOrder } from "./data";
+import { Camera, Material, Matrix4x4, Node, Scene, preOrder } from "./data";
 import { IndexBuffer, IndexBufferProps, Texture2D, Texture2DProps, VertexBuffer, VertexBufferProps } from "./resources";
 import { ShaderFlagKey, ShaderFlags, createPipeline, shaderFlagsKey } from "./shader";
 
+const _normalMatrix = new Matrix4x4(
+	NaN, NaN, NaN, NaN,
+	NaN, NaN, NaN, NaN,
+	NaN, NaN, NaN, NaN,
+	NaN, NaN, NaN, NaN,
+);
+
 export class Renderer {
 
 	_adapter: GPUAdapter;
@@ -391,10 +398,18 @@ export class Renderer {
 			const offset = this._uniformWriter._length;
 			object._updateWorldMatrix();
 			this._uniformWriter.writeMatrix4x4(object._worldMatrix);
-
+			this._uniformWriter.writeMatrix4x4(_normalMatrix.setObject(object._worldMatrix).inverseTransposeAffine());
 			return offset;
 		});
 
+		// directional lights gather
+
+		// TODO
+
+		// point lights gather
+
+		// TODO
+
 		void materialBindGroups;
 		void objectOffsets;