D2 log 017 – Box2D integration

This was a big one. I switched to Box2D for collision detection & physics.

My old system was nothing fancy: axis-aligned bounding boxes, a “sliding” mechanism for collisions, sector based space subdivision. Worked well for Superforce. However there’s a lot more happening in Devastro 2. More bullets, more particles, more enemies, more complicated level design, player motion needs to be fluid around obstacles etc. Box2D seems like the right tool for that job.

First I had to rip out large amounts of old code both in the game and the editor. Everything was completely broken for over a week. Fortunately the Box2D integration went well and the game is now back up and running.

The Box2D API is nice and there’s plenty of documentation & example code.

Box2D

D2 log 016 – Texture atlas inspector

To improve rendering performance the game builds a texture atlas from all the images. This process is quick enough to be done at load time. I wanted to have a clear idea about the atlas layout. Xcode does have some support for viewing OpenGL textures but it’s been crashing on me almost every time I used that feature. So I did what I usually do when a 3rd party tool fails me: I built my own inspection tool to look at the OpenGL textures directly in-game.

Even in its initial simple form it has already helped fix a few issues.

I’m planning to extend it with zoom & pan and a way to track usage of the individual images in the atlas.

Development tools 2019

Here is a list of development tools I’m using at the moment.

Hardware

  • iMac retina 27″ 2015, 32GB RAM
  • iPhone SE
  • iPad Mini 4
  • XBox wireless controller

Software

Libraries

Notes

  • Recent versions of Photoshop have been not so great. Pixelmator development has almost ceased. Considering switching to Affinity Photo.
  • Starting to use Blender for 2D vector graphics as well (icons etc).

Previous installments

2006201220142017

Git activity graph

Number of commits is not a good metric for productivity, project health or anything else really. But let’s pretend! It may be OK as a simple activity indicator…

Here’s a Python script I made that graphs daily commit counts on a git repository by year.

Download the script here. Requires Python 3 and PIL/Pillow.

Usage:

pip3 install pillow
python3 activity.py /path/to/imgui imgui

Output:

imgui-2014.png
imgui-2015.png
imgui-2016.png
imgui-2017.png
imgui-2018.png
imgui-2019.png

Example output for imgui:

D2 log 015 – Load time improvements

As I keep adding assets to the game, the load time keeps increasing. Who would have thought? A 5 second startup may not sound like much but it quickly adds up during development.

One way to fix it would be to load assets on demand. This might cause stuttering, but that’s OK for development. However, improving the load time would benefit the final game as well. Let’s do that!

I added a job system that allows the preload to happen on multiple threads. Load time: 1.5 seconds. Nice! Now that I’ve “jobified” the tasks that need to run, further improvements can be made with relatively little effort.

Inspiration:

 

D2 log 014 – Video player

The main menu of the game is going to have an animated background. Currently I’m thinking it could be the end of the original trailer put on loop:

As a temporary playback solution I used a series of JPEG files. Not very efficient. When looking for a decent video playback library, I found this one:

A brand new “single-header” library for decoding MPEG1 video, by Dominic Szablewski. Simple API, easy to integrate. It’s great!

In fact, I spent more time looking for my .blend source file than writing code to use the library. In Blender, I switched render output from image to video and set the codec to MPEG1. It all worked the first time I ran the game.

D2 log 012 – Blender pipeline

The new Blender 2.8 is great. Unfortunately it broke my batch render script.

Fixing the script and the rendering setup were quite a challenge due to the major UI changes in 2.8, but eventually I figured it out. Even learned a few new tricks along the way. How did I manage to write the original script without the built-in scripting console? So helpful!

My Blender export pipeline looks like this:

  1. master.blend file with fixed camera & lighting setup
  2. extra .blend file for each asset
  3. link assets into master
  4. for each asset, render object & shadow into separate PNG

First draft of the new script for 2.8:

import bpy
import os
import subprocess

# Requires Blender 2.8
#
# /Applications/blender.app/Contents/MacOS/Blender -b -P render28.py
#
# Notes:
# 
# Node setup: see master.blend -> Compositing
# Render menu -> Film -> transparent
# Shadow catcher plane -> Object menu -> Visibility -> Shadow catcher
# Adding more objects: File -> Link... -> "Collection" from ext. file -> Move to Assets collection in master

basepath = os.path.normpath(os.path.dirname(os.path.abspath(__file__)))
master_blend = "blender28-batch-render-test-master.blend"

src = os.path.join(basepath, master_blend)

bpy.ops.wm.open_mainfile(filepath=src)

bpy.context.scene.render.resolution_percentage = 50
bpy.context.scene.render.resolution_x = 1280
bpy.context.scene.render.resolution_y = 960
bpy.context.scene.cycles.samples = 20

assets_name = "Assets" # name of collection in master.blend
assets_collection = None

for collection in bpy.data.collections:
	if collection.name == assets_name:
		assets_collection = collection
		break

if assets_collection is None:
	print( "Error: %s collection not found in master" % assets_name )
	quit()

# Save original filenames for output nodes
output_nodes = []
for node in bpy.context.scene.node_tree.nodes:
	if ( node.type == "OUTPUT_FILE" ):
		output_nodes.append( ( node, node.file_slots[0].path ) )

for target in assets_collection.objects:
	# Show only the current object
	for obj in assets_collection.objects:
		obj.hide_render = obj.name != target.name

	# Set output filename
	for node, path in output_nodes:
		node.file_slots[0].path = target.name + "_" + path

	bpy.ops.render.render(animation=False)

Master & test .blend files here: blender28-batch-render-test.zip

Example output:

Object
Object

Shadow
Shadow

Composite
Composite

Additionally, I created a simple pipeline for rendering weapon silhouettes for the HUD. With a single click, it pulls in each weapon model, renders it from a side-view, then uses just the alpha to write a single-color transparent PNG.

And similar setup for pickup icons, with a subtle “glow” pass.