Subscribe to GameFromScratch on YouTube Support GameFromScratch on Patreon

25. April 2016

 

One of the major advantages to working in 3D is once you have your character modeled and rigged, creating new animations is simply a matter of defining a series of poses on a timeline.  Animations are generally defined by moving a series of bones controlling your mesh, which in turn are powered by a system called inverse kinematics.  IK is basically a fancy way of saying “move an end bone and the computer will calculate how all the other bones in the chain will respond” enabling you to animate by positioning the foot forimage example and the ankle, knee and hip will rotate appropriately.  It’s a pretty powerful way to perform animation and every single major 3D application implements IK (and FK – forward kinematics).

 

In the land of 2D art, the process is often quite different.  Generally the approach here is to generate a sprite sheet, which is a sequence of slightly altered versions of the same character, which played in sequence results in an animation.  If you ever done a flipbook animation at the top corner of any of your textbooks, you already have the process of traditional 2D animation down.  There are other techniques such as onion skinning and rotoscoping to aid in the animation process, but it still remains time intensive.  If only there was some way to take the 3D worlds bone based animations and apply them to generating 2D art?  Well, there is... Spine.

 

Today we are going to look inside Spine, look at the art generation process, how to make sprite graphics that are animation ready, define an animation, then perhaps most importantly, play that animation back in our game engine of choice.  Since Spine itself is built over top of the LibGDX library (by one of the frameworks founders to boot), therefore I suppose a LibGDX example makes the most sense.  If you are bored, the story of how Spine came to be is an interesting read.

 

Full disclosure, I requested a review license in order to get hands on time with Spine.  Additionally some of the assets I am using in this demonstration are part of asset packs available for purchase and aren’t my creation.  Spine is commercial software, ranging in price from $70 for the essentials version, $300 for professional and $2200 for enterprise (which is tied to your companies revenue).  There is a free trial available and capable of doing everything we are about to do below except export and run in code.  Without further ado, let’s jump in.  As is often the case on GameFromScratch, if you prefer a video version one is available here as well as embedded below.

 

Meet Spine

Here is the main Spine interface:

image

 

It’s actually an exercise in simplicity which I appreciate.  It also supports UI scaling, so works well on high DPI displays, something far too many applications suck at, so I also appreciate that.  The left hand viewport is where the magic happens, this is where you compose your characters and animations, while on the right hand side you’ve got your project hierarchy a scene graph of sorts.  The primary UI is across the bottom of the screen.  You can easily pan and zoom around the display using a combination or RMB and Ctrl + RMB.  There is some additional complexity hidden away behind this menu:

image

 

But most of the time, what you see is actually all that you need.  It’s a very clean and simple UI.  Notice in the top left corner it says SETUP.  This is because you are currently in Setup mode.  Once our Sprite has been assembled and our bones have been arranged ( more on this in a moment ), we can then switch in to animation mode by clicking SETUP.

image

In animation mode, its all about posing our character.  Notice SETUP changes to ANIMATE and our interface changes slightly.  Now we have a timeline across the bottom of the screen.  We will get back to that in a moment.

 

Creating Spine Ready Sprites

Creating a sprite that is ready to be animated in Spine is pretty close to traditional sprite based animation with two major exceptions.  First, you cut your image up into several different pieces.  You can draw your sprite as a single image if you wish, but once you are done you need to cut it into several different animatable pieces.  Consider the sprite from the above screenshots:

image

This looks like a single drawn sprite, but it’s actually made up for several pieces arranged together.  If you look in the images section of the hierarchy, you can see it’s actually composed of several different images:

image

 

Again, you can draw your sprite how you normally would, but each animatable piece will need to be cut up to proceed in Spine.  This leads to our second requirement...  you also need to draw parts of the images that are normally obscured.  Again, using this example, even if the upper arm isn’t full shown due to being obscured by the body you still need to draw the entire arm, as the visibility can change as the sprite moves, for example:

imageimage

 

So when drawing the pieces of your sprite, you have to think about the depth as well.  Here for example are all the pieces that go together to make this character:

image

 

Rigging Your Character

Next up comes perhaps the most time intensive portion of working with Spine, rigging you character.  You can think of this as arranging all the various images together to create your character, while defining the underlying armature (fancy word for skeleton).  We will do a very simple skeleton, just to demonstrate the process.  You will notice in the tree view that there is a root node under our skeleton:

image

 

This is the very base of the skeleton and all bones are parented to it ultimately.  From here we need to create a root bone, it’s very common to start from the hips, which is what we will do.  Using the create tool, we will quickly create a simple leg skeleton:

image

Click once to set the start of the skeleton, then move the mouse and click again to set the first bone.  Now move down slightly and set another bone, like so:

image

In the hierarchy I rename the bones to values that make sense.

image

Now that we have bones, let’s attach some images to each.  From the images section you can simply drag the appropriate image onto the bone, like so:

image

You will be prompted if you want to go ahead with it:

image

 

The image is now parented to that bone.  By selecting the image you can now transform, rotate and resize it so it best matches the underlying bone:

image

You can also modifying the bone length by hovering over the tip, like so:

GIF

 

Now repeat for the lower bone, like so:

image

 

You end up with a hierarchy like:

image

 

Extremely simple, but the character is rigged, well, the leg is anyways.

 

Creating an Animation

 

Now that we have a very simple animatable character, let’s now switch over to ANIMATE mode.  In the tree view, you should see a section called Animations.  There may be a default one there, otherwise create one using the New Animation button that appears when animation is selected:

image

image

 

Keyframed animation is pretty simple in concept.  You will notice at the bottom of the screen there is now a Dopesheet view:

image

 

Your animation is composed of a set of “key” frames.  That is, you post your character and take a snapshot of the location/rotation/scale of a given bone, then advance the timeline to a different value and repeat the process.  The computer then interpolates between keyframes to create a smooth animation.  You can turn “autokey” on, so that any changes you make in the editing window automatically set a key.  Otherwise you can manually create the key by clicking the green key to the right of each transform:

image

 

Set a key for the default rotate, translate and scale values, or use Autokey.  Next advance the timeline to say 5, like so:

image

 

Next using rotations, manipulate each bone, like so:

gif2

 

Advance the timeline slightly more, then repeat the process all over again.  You can control the playback of your animation using these simple VCR style controls:

image

 

Here is a very simple and crude kicking animation:

gif3

 

Another cool thing you can do is add Events as part of your timeline, like so:

image

image

Enabling you to create events that can be fired in code, allowing you to incorporate programmatic aspects into your animations, such as playing a footstep audio effect.  We will see this process shortly.

 

Exporting the Animation

Now that we’ve got an animation to use in our game, it’s time to export it.  Here there are a couple of choices. 

image

 

You can export your results as a video, a sequence of images or as data.  If you chose to export as an image you can actually have some rather advanced controls, including generating a texture atlas (directly usable in LibGDX) or sprite sheet:

image

 

With results like:

skeleton-kick

 

This approach can be utilized in just about every single kind of game engine available today.  However, where Spine shines is when you chose to export as data instead.  This is where runtimes come in.  These are essentially libraries or code for the various game engines that enable you to use spine format natively.  Full source is available on github and runtimes exist for most 2D engines available including Unity, LibGDX, Love, MonoGame, Torque2D, Cocos2d-x and many more.  In this example I will be using LibGDX.

 

In this case I’m going to export to JSON and generate a texture atlas using the following settings:

image

 

Now let’s break out some code.

 

Using Spine In Game

As mentioned earlier Spine have several runtimes available on github.  In the case of the LibGDX project, you simply have to copy the code into your appropriate source code folder.  Assuming you created a project using the setup utility, this means copying the contents of esotericsoftware to your core\src\com directory.  Then I wrote the following code, adapted from one of their LibGDX examples.

Make sure that you’ve exported your assets and created the atlas in your working directory, most likely \core\assets.  Then use the following code:

package com.gamefromscratch;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.graphics.g2d.TextureAtlas;
import com.esotericsoftware.spine.*;

public class Spine2 extends ApplicationAdapter {
    private OrthographicCamera camera;
    private SpriteBatch batch;
    private SkeletonRenderer renderer;
    private TextureAtlas atlas;
    private Skeleton skeleton;
    private AnimationState state;

	public void create () {
		camera = new OrthographicCamera();
        camera.setToOrtho(false);
		batch = new SpriteBatch();
		renderer = new SkeletonRenderer();
		renderer.setPremultipliedAlpha(true); // PMA results in correct blending without outlines.

		atlas = new TextureAtlas(Gdx.files.internal("skeleton.atlas"));
		SkeletonJson json = new SkeletonJson(atlas);
		SkeletonData skeletonData = json.readSkeletonData(Gdx.files.internal("skeleton.json"));
		skeleton = new Skeleton(skeletonData);
		skeleton.setPosition(0, 0);

		AnimationStateData stateData = new AnimationStateData(skeletonData);
		state = new AnimationState(stateData);

        // Set up an animation listener so we can respond to custom events or completion
        final AnimationState.TrackEntry track = state.setAnimation(0, "kick", false);
        track.setListener(new AnimationState.AnimationStateListener() {
            @Override
            public void event(int trackIndex, Event event) {
                // Check for the "half" event we defined in the editor
                if(event.getString().equals("half"))
                    System.out.println("Half way baby");
            }

            @Override
            public void complete(int trackIndex, int loopCount) {
                // or the complete event (not END!) when done, fire the idle animation instead
                state.setAnimation(0,"idle",false);
            }

            @Override
            public void start(int trackIndex) {
            }

            @Override
            public void end(int trackIndex) {
            }
        });
	}

	public void render () {
		state.update(Gdx.graphics.getDeltaTime()); // Update the animation time.
		state.apply(skeleton);
		skeleton.updateWorldTransform();

        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
		camera.update();
		batch.getProjectionMatrix().set(camera.combined);
		batch.begin();
		renderer.draw(batch, skeleton);
		batch.end();
	}

	public void dispose () {
		atlas.dispose();
	}
}

 

When you run this code...

gif4

 

In the above code example you can see how you can handle an event you defined in Spine.  Otherwise it’s pretty simply to load and play animations on a character developed in Spine.  There is a comprehensive API, I’ve only touched on a very small part of it here due to space (this is already pretty long...).  There are also several features I never got to mention such as free form deformation ( useful for shapes such as capes ), swappable skins, place able props, etc..  If you are doing 2D animation, Spine is certainly a product you should check it.  Spine is by no means the only option when it comes to 2D animation in games, Spriter and Creature are two other popular alternatives.  It is however a very good option.

 

The Video

Art, Programming , ,

20. April 2016

 

One of the advantages to moving to a subscription model is we now see continuous project improvement instead of a massive dump of features every couple of years.  Maya has taken the approach of extending via the extensions releases.   They just released the second set of extensions for Maya 2016.

New features include:

  • a new render setup system enabling artists to group and configure objects as they prefer
  • new animation blend shape system with updated UI
  • new tools for creation of blend shapes
  • new post space deformation system (PSD) enable sculpted changes on a per pose basis
  • new quick rig system via HumanIK
  • new xgen system for hair creation
  • added motion graphics toolset, procedural geometry system

 

For a comprehensive demonstration of new UV and modelling changes watch the following (extremely quite...) video:

 

You can read more about this release here.

Art, GameDev News ,

18. April 2016

 

Over on the Autodesk AREA blog Autodesk just announced the new features in the upcoming 3ds Max 2017.  3D Studios Max is a long running 3d content creation application, perhaps most often used for game development.  It seems there are several new features coming in the 2017 release.

New features include:

  • an updated UI and High DPI monitor support
  • viewport performance improvements, up to 300%
  • improvements to performance and usability of Unwrap UVW including:
    • Dramatic Performance improvements
    • New Packing Algorithm
    • New Peeling based on ABF(Angle Based Flattening)
    • Point-to-Point Selection Preview
    • Symmetrical Geometry Selection 
    • Loop Selection and Ring Selection
    • Display Only Selected Polygon in viewport
  • a new ray tracer, ART (Autodesk Raytracer Renderer)
  • new Physical material for replicating real world surfaces
  • new Sun Positioner
  • new Scene Converter to ease move to different renderers or game engines
  • scanline renderer multi core support scaled to 128 cores
  • modeling object tool improvements, including:
    • local align
    • sub object picking
    • point to selection
    • boolean and hard surface modeling improvements
  • animation controllers
  • custom attributes
  • python integration
  • skin weighting with geodesic voxel and heat map skinning
  • new text and shape tools

You can see several of the new features in this montage video

Art, GameDev News ,

29. March 2016

 

Welcome to the second Blender how to ( here is the first ), a series of quick step by step tutorials showing you how to accomplish a specific task using Blender.  Today we will look at a way of quickly modeling a high rise building.  It assumes you know the basics of using Blender.  If you don’t, no worries, I have tutorials for that!

 

First, start with the default cube, like so:

image

 

Now enter edit mode(TAB) and  loop cut (CTRL + R) it about the center, like so:

image

 

Select all the faces of the top half and separate them (P->Selection)

image

 

In object mode move the newly separated top portion up along the Z axis (G + Z + mouse)

image

 

Select the bottom box, make a copy (SHIFT + D), then move it up along the Z axis.

image

 

Select the middle piece, switch to edit mode, select the bottom face and delete it (x –> faces), like so:

image

 

This face is going to represent the various floors of your building.  Keep the top and bottom edges the same size as the top/bottom box and start carving it up to match your floor.  I generally start by doing a pair of loop cuts along the entire length, like so:

image

This can be accomplished by doing a loop cut (Ctrl + R), then before clicking to commit, scroll button once to perform multiple evenly spaced cuts at once.  Next I move them up and down the mesh simultaneously by simply scaling along the Z axis (S, Z, mouse move)

Now lets do several more loop cuts for windows using the same process (Ctrl + R, Mouse wheel multiple times):

image

 

Next select every other edge created (alt + shift click to select multiple) like so:

image

 

We now want to edge slide the selected edges (G,G)

image

Now select the inner faces like so:

image

Then hit E to extrude them

image

Repeat the similar process on all 4 sides to define your building.  Obviously you would arrange as you saw fit.

 

Now that we have our floor defined, it’s time to make a lot of them.  Switch to object mode then go to the modifiers tab and select Array:

image

 

Now we need to make sure we set the axis to array along ( set Z to 1 in the relative offset area ) and the number of times to duplicate under the count section.

image

When satisfied, click the Apply button.  Finally move your top and bottom pieces so they cap the building on each end, like so:

image

 

Select all 3 shapes and merge them together (Ctrl + J) like so:

image

Now we just need to weld our objects together.  Box select (B) the overlap area between the bottom and middle boxes in edit mode, like so:

image

Now select Remove Doubles in the Tool menu(T), then manipulate the Merge distance

image

Until you see

image 

Repeat for the top portion.

 

TADA, a building in Blender.  An ugly building mind you, but a building none the less.

image

Art ,

21. March 2016

 

Blender 2.77 is finally out, you can download it here.  Taking a bit longer than previous releases, this version brings a number of new features, including:

  • Cycles rendering improvements including GPU support for Smoke/Fire, Subsurface Scattering and more
  • Massive Grease Pencil improvements (including 2D animation)
  • OpenVDB caching for large simulation datasets
  • UI improvements
  • Improved painting and sculpting tools
  • Edit mode booleans
  • UVMap on creation of primitives
  • And much much more

 

When Blender 2.77RC2 was released, I put together a video highlighting major new features of this release.  You can view it here or embedded below.

Art, GameDev News

Month List

Popular Comments