From 5f1d1eccb087be7d278d21968e8c3cc989a7e932 Mon Sep 17 00:00:00 2001
From: Jozufozu <jozsefaug@gmail.com>
Date: Thu, 18 Jan 2024 17:23:18 -0800
Subject: [PATCH] Monster mat

- Tweak the matrix and quaternion utility shaders.
---
 .../flywheel/instance/cull/oriented.glsl      |  2 +-
 .../flywheel/flywheel/instance/oriented.vert  |  4 +--
 .../assets/flywheel/flywheel/util/matrix.glsl | 33 ++++++++++++++-----
 .../flywheel/flywheel/util/quaternion.glsl    | 25 ++++++++------
 4 files changed, 42 insertions(+), 22 deletions(-)

diff --git a/src/main/resources/assets/flywheel/flywheel/instance/cull/oriented.glsl b/src/main/resources/assets/flywheel/flywheel/instance/cull/oriented.glsl
index d38a3b58c..804fd9597 100644
--- a/src/main/resources/assets/flywheel/flywheel/instance/cull/oriented.glsl
+++ b/src/main/resources/assets/flywheel/flywheel/instance/cull/oriented.glsl
@@ -5,5 +5,5 @@ void flw_transformBoundingSphere(in FlwInstance i, inout vec3 center, inout floa
     vec3 pivot = i.pivot;
     vec3 pos = i.position;
 
-    center = rotateVertexByQuat(center - pivot, rotation) + pivot + pos;
+    center = rotateByQuaternion(center - pivot, rotation) + pivot + pos;
 }
diff --git a/src/main/resources/assets/flywheel/flywheel/instance/oriented.vert b/src/main/resources/assets/flywheel/flywheel/instance/oriented.vert
index dc96d1d7f..9b3e39906 100644
--- a/src/main/resources/assets/flywheel/flywheel/instance/oriented.vert
+++ b/src/main/resources/assets/flywheel/flywheel/instance/oriented.vert
@@ -1,8 +1,8 @@
 #include "flywheel:util/quaternion.glsl"
 
 void flw_instanceVertex(in FlwInstance i) {
-    flw_vertexPos = vec4(rotateVertexByQuat(flw_vertexPos.xyz - i.pivot, i.rotation) + i.pivot + i.position, 1.0);
-    flw_vertexNormal = rotateVertexByQuat(flw_vertexNormal, i.rotation);
+    flw_vertexPos = vec4(rotateByQuaternion(flw_vertexPos.xyz - i.pivot, i.rotation) + i.pivot + i.position, 1.0);
+    flw_vertexNormal = rotateByQuaternion(flw_vertexNormal, i.rotation);
     flw_vertexColor = i.color;
     flw_vertexLight = i.light / 15.0;
 }
diff --git a/src/main/resources/assets/flywheel/flywheel/util/matrix.glsl b/src/main/resources/assets/flywheel/flywheel/util/matrix.glsl
index af8fb301b..0b5e8eabd 100644
--- a/src/main/resources/assets/flywheel/flywheel/util/matrix.glsl
+++ b/src/main/resources/assets/flywheel/flywheel/util/matrix.glsl
@@ -1,20 +1,35 @@
-mat4 rotate(vec3 axis, float angle) {
+mat3 rotation(vec3 axis, float angle) {
     float s = sin(angle);
     float c = cos(angle);
     float oc = 1. - c;
 
     vec3 sa = axis * s;
 
-    mat4 mr = mat4(1.);
-    mr[0].xyz = oc * axis.xxz * axis.xyx + vec3(c, sa.z, -sa.y);
-    mr[1].xyz = oc * axis.xyy * axis.yyz + vec3(-sa.z, c, sa.x);
-    mr[2].xyz = oc * axis.zyz * axis.xzz + vec3(sa.y, -sa.x, c);
-
-    return mr;
+    return mat3(
+    oc * axis.xxz * axis.xyx + vec3(c, sa.z, -sa.y),
+    oc * axis.xyy * axis.yyz + vec3(-sa.z, c, sa.x),
+    oc * axis.zyz * axis.xzz + vec3(sa.y, -sa.x, c)
+    );
 }
 
-mat4 rotation(vec3 rot) {
-    return rotate(vec3(0., 1., 0.), rot.y) * rotate(vec3(0., 0., 1.), rot.z) * rotate(vec3(1., 0., 0.), rot.x);
+mat3 rotationDegrees(vec3 axis, float angle) {
+    return rotation(axis, radians(angle));
+}
+
+/*
+ * Create a rotation matrix that rotates the vector `from` to `to`.
+ * https://iquilezles.org/articles/noacos/
+ */
+mat3 rotationAlign(in vec3 from, in vec3 to) {
+    vec3 v = cross(from, to);
+    float c = dot(from, to);
+    float k = 1. / (1. + c);
+
+    return mat3(
+    k * v * v.xxx + vec3(c, -v.z, v.y),
+    k * v * v.yyy + vec3(v.z, c, -v.x),
+    k * v * v.zzz + vec3(-v.y, v.x, c)
+    );
 }
 
 mat3 modelToNormal(mat4 mat) {
diff --git a/src/main/resources/assets/flywheel/flywheel/util/quaternion.glsl b/src/main/resources/assets/flywheel/flywheel/util/quaternion.glsl
index 8db184956..51591518d 100644
--- a/src/main/resources/assets/flywheel/flywheel/util/quaternion.glsl
+++ b/src/main/resources/assets/flywheel/flywheel/util/quaternion.glsl
@@ -1,12 +1,13 @@
-#define PI_OVER_2 1.5707963268
-
-vec4 quat(vec3 axis, float angle) {
-    float halfAngle = angle * PI_OVER_2 / 180.0;
-    vec2 cs = sin(vec2(PI_OVER_2 - halfAngle, halfAngle)); // compute sin and cos in one instruction
-    return vec4(axis.xyz * cs.y,  cs.x);
+vec4 quaternion(vec3 axis, float angle) {
+    float halfAngle = angle * 0.5;
+    return vec4(axis.xyz * sin(halfAngle), cos(halfAngle));
 }
 
-vec4 quatMult(vec4 q1, vec4 q2) {
+vec4 quaternionDegrees(vec3 axis, float angle) {
+    return quaternion(axis, radians(angle));
+}
+
+vec4 multiplyQuaternions(vec4 q1, vec4 q2) {
     // disgustingly vectorized quaternion multiplication
     vec4 a = q1.w * q2.xyzw;
     vec4 b = q1.x * q2.wzxy * vec4(1., -1., 1., -1.);
@@ -16,11 +17,15 @@ vec4 quatMult(vec4 q1, vec4 q2) {
     return a + b + c + d;
 }
 
-vec3 rotateVertexByQuat(vec3 v, vec4 q) {
+vec3 rotateByQuaternion(vec3 v, vec4 q) {
     vec3 i = q.xyz;
     return v + 2.0 * cross(i, cross(i, v) + q.w * v);
 }
 
-vec3 rotateAbout(vec3 v, vec3 axis, float angle) {
-    return rotateVertexByQuat(v, quat(axis, angle));
+vec3 rotateAxisAngle(vec3 v, vec3 axis, float angle) {
+    return rotateByQuaternion(v, quaternion(axis, angle));
+}
+
+vec3 rotateAxisAngleDegrees(vec3 v, vec3 axis, float angle) {
+    return rotateByQuaternion(v, quaternionDegrees(axis, angle));
 }