1. Blender API: Part 2: Game Engine
Roger Wickes

2. Game Engine Use Blender to model, UV texture, animate, etc.
Makes a Windows .exe file for royalty-free distribution for PC play only
Competes with Unity, Lumberjack
Each object has a logic tree, evaluated at a Frame Rate:
Sensor-Controller-Actuator (SCA)
Sensors: keyboard, joystick, network, timer, always, ray, radar, near, collision
Controllers: And, Or, etc. Python Script or Module
Actuators: Motion, Message, Camera, Scene, Constraint, Action, …
Actions via any kind of shape keys, bone-actions.
Triggered by sensor – event or timer (e.g. idles)
Animated textures via sprites sheets, sequences, or movies. Standard color diffuse, normal bump maps, reflection (spec) maps. Particles work as well
Objects can be subject to physics: gravity, force fields
Motion can be recorded for use in non-game action

3. Python API (Controller)
#Land Mine methods
import bge, bpy
def Explode(controller):
obj = controller.owner
hide(obj)
sprite = Sprite(obj, ‘FIREBALL’)
print(“%s exploded.” % obj.name)
def hide(obj):
# move object to non-game layer
# so it cannot explode again
pass
Class Sprite():
def __init__(self, obj, sheet):
# create textured plane with sheet
# put plane at obj position
# orient to face scene camera
# play animation once
# call back to remove plane from scene
Import bge
Import GameLogic
Import Physics
Real-time debugging

4. dir(bge) ‘app’ – the blender application itself; version
Special mention: bpy.game

5. World setup Sets background; can be color or image texture
Use HDR images for a world and observable sky
Mist helps with Occluding far off objects not of interest

6. Scene setup Blender Render Set Blender Game renderer
Set Gravity (if you use Rigid Bodies)
Rigid Body World
Set Blender Game renderer
Enables Nav Mesh for path finding
LoD for performance

7. Object setup
Actor
Collision bounding box shape

8. Demos
Spin – simple motion showing S-C-A and in-game messaging. The empty fires off a message to Bullet that starts it’s motion. Shows Local vs Global motion. Shows animated materials (changing color). Shows use of Mist.
Drop – uses physics to drop stuff in place. Demonstrates the collision and timer sensors on cylinder.008
Keyboard – processes keyboard input. Note camera parenting to the player called camera following. Shows keyboard sensor and event processing from the sensor stack, dynamically configuring an actuator (the motion sensor), gates (for level complete), and overlaying scenes.

9. Helpful Hints
Actions (like transpose/move) can be either Local to the object’s axis, or Global to the world axis
Mass is relevant to collisions; how much one deflects the other is vectored to their relative masses
Show console (on Windows: Window->Toggle System Console; Linux start Blender from a console window) to see print() statements.

10. Tips
Change the rendering engine in the Info window header to Blender Game-reveals a lot of game options in the menus
Code and debug inside Blender for instant feedback
Use Code colors
Try dir(bpy.game) in a python controller (has to be while game is running)
Hover over a UI element to see the API call being made