Godot

Name	Description
Vertex / Vertices / Point	點
Edge / Line	線
Face	面
Mesh / Polygon	多面體，Vertex / Edge / Face 的集
Concave	由 Face 組成的多面體
Convex	由 Vertex 組成的多面體
Magnitude	Vector Length / 向量的長度

Cons

• Node structure (Not ECS)
• Rigid / Kinematic / Static is separate, and some common method is missing
• 3D Physics method not complete
• PhysicsDirectBodyState is singleton !?
• PhysicalBone does not have velocity method
• PhysicsBody transform does not sync with PhysicsServer
• Lack physics doc

Joint

• Will use node.GlobalTransform.origin - joint.GlobalTransform.origin as anchor point

# Reference: bullet\BulletDynamics\ConstraintSolver\btGeneric6DofConstraint.cpp

Impulse = LimitSoftness * (Restitution * Depth / TimeStep - Damping * RelativeVelocity) * jacDiagABInv;

Pin Joint

• 保持 固定距離，固定距離 = 建立 Pin Joint 時的距離
• Damping (阻尼)：和 固定距離 越近時，引力的相反方向作用力，> 1 會使 相反方向作用力 > 引力
• Impulse Clamp：最大引力

Singleton

Reference

• Project ▶ Project Settings ▶ Autoload
  • Can be class (.cs / .gd) or scene (.tscn)
  • Class must inherit from Godot.Node
  • Class will be instanced and add to root
• Run flow
  • Autoload
  • Main scene

using Godot;
using System;

public class Global : Godot.Node
{
    public override void _Ready()
    {
        // CurrentScene
        // Viewport root = GetTree().GetRoot();
        // root.GetChild(root.GetChildCount() - 1);
    }
}

Editor 3D Navigation

• Hold RMB / Shift + F to enter fly mode
  • W S A D to move forward / back / left / right
  • E Q to move up / down
  • Shift Alt to speed up / down
• MMB to rotate

Unhandled Exception Policy

Do not terminate application on unhandled exception

• Project Settings
  • Mono
    • Unhandled Exception Policy

Dot Product

• A, B is Vector3
• Dot(A, B) return float
• Dot(A, B) 可用於計算 A, B 的角度
  • > 0 時角度 < 90
  • = 0 時角度 = 90
  • < 0 時角度 > 90
• Dot(A, B) = A.X * B.X + A.Y * B.Y + A.Z * B.Z
• Dot(A, B) = (A.Length * B.Length) * Cos(A.AngleTo(B))
• A.AngleTo(B) = ACos(Dot(A, B) / (A.Length * B.Length))
  • If A and B normalized
    • A.AngleTo(B) = ACos(Dot(A, B))

Cross Product

• A, B is Vector3
• Cross(A, B) return Vector3
• Cross(A, B) 垂直於 A, B 這個平面
• Cross(A, B) = -Cross(B, A)
• 可用於計算 Torque (扭力)

Mathf

// Pseudo Code
float Clamp(float value, float min, float max)
{
  if (value < min) return min;
  if (value > max) return max;
  return value;
}

// Pseudo Code
float Wrap(float value, float min, float max)
{
  float range = (max - min);
  if (value >= max) 
    return Wrap(value - range, min, max);
  if (value <= min)
    return Wrap(value + range, min, max);
  return value;
}

Physics

• Only change physics related properties (Velocity) in _integrate_forces()
  • Reference
  • Use PhysicsDirectBodyState.step to get delta
  • GetCollidingBodies() use much CPU

FPS

// FPS
Engine.TargetFps

// Physics FPS
Engine.IterationsPerSecond

Input

// Input.IsActionJustPressed() can be used in _PhysicsProcess() / _Process()
// Godot will auto detect
public override void _PhysicsProcess(float delta)
{
    Input.IsActionJustPressed();
}

public override void _Process(float delta)
{
    Input.IsActionJustPressed();
}

Ref: input.cpp