Category Archives: Devastro2

D2 log 021 – Input replay

New debug feature added to the game: recording inputs during gameplay and playing them back later.

This helps me reproduce a given scenario with a single button press. I can also do a Quake-style “timedemo” recording and use it as a performance benchmark.

To make replay work properly, I had to set a constant seed in my random number generator and make sure all entities were using it. The storage format is not optimal. Recording a long session would probably use more disk space than necessary. But we’re still talking a few kilobytes per minute, so it’s fine.

D2 log 020 – SDL port

I upgraded my home machine to macOS Catalina. Big mistake.

  • Zero interesting new features
  • Devastro 2 OpenGL renderer broken
  • Left 4 Dead unplayable (oh no!)

My OpenGL window went black. Was I using OpenGL wrong? How? On my quest for the answer, I ended up rewriting significant parts of the rendering core, updated all my shaders and created a new SDL port. It took several nights to get things working again.

The good thing is that switching to SDL was one of my mid-term goals anyway. I’m going to need it on Windows. To complete the port, I added SDL event handling and audio backend.

Event inspector for testing the SDL port. Blatantly copied from Sokol.

It was nice to get rid of the Cocoa boilerplate. One thing I missed in the SDL API was a function to set a fixed aspect ratio for my window. I had to do it like this:

cocoa.m:

#import <Cocoa/Cocoa.h>

void SetWindowRatio(void *window) {
    NSWindow *win = (__bridge NSWindow*) window;
    win.aspectRatio = NSMakeSize( 1280, 720 );
}

main.cpp:

#include <SDL.h>
#include <SDL_syswm.h>

extern "C" void SetWindowRatio(void *window);

// and later..

SDL_SysWMinfo wmInfo;
SDL_VERSION(&wmInfo.version);
SDL_GetWindowWMInfo(sdl.window, &wmInfo);
SetWindowRatio(wmInfo.info.cocoa.window);

Fixing Left 4 Dead was easy. Add a new APFS volume, install Mojave, install Steam, move data files over, tell Steam to use them → no need to re-download everything. The nice thing about APFS volumes is that they share space, so I don’t have to think about how big each partition should be.

D2 log 019 – Level editor loose ends

I’ve been neglecting the level editor a little bit. It didn’t get fully updated with IMGUI, mainly because it was a mess. It had gone through the entity system development with only quick updates here and there and it showed.

Last night I decided it was finally time to dig in. After an hour or two of cleanup and refactoring, things started looking much better. I wrote new entity & variant selection lists and fixed a few bugs related to Box2D. Overall line count went down, which is always a good sign. So much for custom UI components!

D2 log 018 – Easing curve previews

During a recent rewrite of the menu system, it occurred to me it would be nice to have a visual preview of the various animation easing curves available in the engine.

So I made a tool to do that. Pick an easing function, see the curve and an animation showing its effect on alpha, scale and position. 20 minutes, 150 lines of code.

This will make it much easier to pick the right function when creating new UI and in-game animations.

Luckily I’m done with the menus for now. If I ever need to add more polish, I might attach this new interface directly to the actual element being animated. That would make this a real WYSIWYG tool.

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.

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.