animation in minecraft movement within movement copyright © 2015 – curt hill

Animation in Minecraft

Movement within Movement

Copyright © 2015 – Curt Hill


Introduction• If we created an entity that was a

derivation of EntityCreature it will move– This is part of its inherited behavior– It will move in a semi-random fashion

• If it is modeled with multiple boxes it will move in an unrealistic fashion– It will look like the figure is frozen in a

block of ice and the block is drug around

• Now we set out to fix this

The Modeler

• The derivation of ModelBase contains a render method• In the example this class is

CurtModelEmu

• All the animation work is done in this method or the methods it calls

• The movements we apply here are strictly ornamental– They just make things more realistic


The render method

• This is called multiple times a second

• The parent piece is moved by Minecraft

• We use this method to move appendages

• Not so much move as rotate them on the body or to whatever they are attached


Angles• There are three angle properties in

ModelRenderer– Recall that each box is an object of this

type

• rotateAngleX, rotateAngleY and rotateAngleZ

• These determine the angles of the box– For the parent this is relative to the

coordinate system– For children this is relative to the parent

and attachment point


Interlude on Angles• Most of us are used to measuring

angles in degrees• Java only believes in radians for

measuring angles– Java follows mathematics and science

in this belief

• There are 2π radians in 360°• A good article as to why radians

are superior is:http://www.purplemath.com/modules/radians.htm


Table


Degrees Radians1 0.0174532925230 0.523598775645 0.785398163457.29577951 160 1.047197551290 1.5707963268120 2.0943951024180 3.1415926536

Angles Again

• Like a good mathematician I will only use radians in code and examples

• If you are stuck in bad practice use this conversion function:

• float degToRad(float deg){return deg*(float)Math.PI/180;}


The rotates

• Each of the rotateAngle variables take radians

• They set the box to that angle immediately

• Typically you wish to avoid large angular changes

• Moreover, you also need to be sensitive to motion of the entity


Disjointed Action

• An appendage rotating has to occur over a time period

• Thus each call to render moves it some distance but not usually the total distance

• We also need to keep track of progress

• There are several practical techniques that we can use


A Counter• We need a counter that tells which

visit to render we are currently in• This is usually an instance variable

of the class– May also be a static local variable of

render

• Each call to render we increment it• We want this value to be in some

range which is usually less than 50– We either divide and keep remainder

or zero it periodicallyCopyright © 2015 – Curt Hill

Selective Actions

• Once the counter is set and in the right range, how do we use it?

• Two good ways:– Use as an index in a constant array to

store the values– Use as the selector in a switch case

• Lets turn the emu’s head in both ways


The Counter in Modeler


@SideOnly(Side.CLIENT)public class CurtModelEmu extends ModelBase{ public ModelRenderer body; public ModelRenderer leg1; public ModelRenderer leg2; public ModelRenderer neck; public ModelRenderer head;

protected int headCycle=0;

The renderEmu


public void renderEmu( CurtEmu ent, float time, float swingSuppress, float par4, float headAngleY, float headAngleX, float par7) { setRotationAngles(time, swingSuppress, par4, headAngleY, headAngleX, par7, ent); body.render(par7); }

Comments• The above two methods will be the

same for both approaches• Notice that we set the angles• Then we render the body• Since the body is the parent, all the

children will also be rendered• The renderEmu routine gets all the

parameters, but I will not use any of them, nor show them here

• Next two versions of renderEmuCopyright © 2015 – Curt Hill

Using a Switch


@Overridepublic void setRotationAngles(…){ switch (headCycle++%20) case 3: head.rotateAngleY = .2F; break; case 4: head.rotateAngleY = .4F; break; case 5: head.rotateAngleY = .5f; break;…

Array


float turns[] = new float[]{0f, 0f, 0f,.2f,.4f,.5f,.5f,.4f, .2f, 0f,0f,-.2f,-.4f,-.5f,-.5f, -.4f, -.2f, 0f,0f, 0f,0f,0f};…@Overridepublic void setRotationAngles(…){ head.rotateAngleY = turns[headCycle++%20]; }

Comparison

• The switch is much more code• In the array fill in gaps that the

switch does not• Also beware of subscripting errors• Once the basic approach is set, it

is easy to make it faster or slower or make the rotation greater or lesser


Motion

• The emu moves its head all the time

• However, you do not want the legs to walk when the emu is standing still

• How do we detect motion?


Entities Again• Entities have several properties of

value here• posX, prevPosX and the

corresponding Y and Z items• Comparing current and previous for

X and Z will tell if this item is moving in the plane or not– Changing Y would be a jump

• We can then test the current and previous and only animate if there is motion


Head wagging• All the suggestions so far given are

synchronous• All the emus will wag their heads at

the same time– Looks unnatural– Not really a problem with walking

• We can vary this by introducing some randomness

• Insert a random object and cancel occasional ticks before the wag


The Final Routines

• In the following screens are the final animations produced in this presentation


setRotationAngles


@Override public void setRotationAngles(…){ setHeadAngle(); setLegAngles(ent);}

setHeadAngle


protected void setHeadAngle(){if(headCycle%20 < 3){ int r = rand.nextInt(10); if(r<6){ headCycle = 0; return; } }head.rotateAngleY = turns[headCycle++%20];}

setLegAngles


protected void setLegAngles (Entity ent){if(ent.prevPosX==ent.posX && ent.prevPosZ==ent.posZ){ // no motion leg1.rotateAngleX = 0f; leg2.rotateAngleX = 0f; legCycle = 0; }else { leg1.rotateAngleX = walks[legCycle++%11]; leg2.rotateAngleX = -leg1.rotateAngleX; }}

Concussion

• Now we are ready to create harmless entities

• Helping non-harmless entities to attack or flee must await the next presentation


animation in minecraft movement within movement copyright © 2015 – curt hill

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