[1.6.4] How to decide rotation angles?

[Ablaze]

Whenever you make a mob, in your render file (I think) there is a setRotationAngles() method right? In that you do all sorts of weird math. Now I never understood how that worked. Can someone tell me how you choose the correct rotation angles for the mob? Or someone explain the math? Or do you guys use a different method I don't know of?

[Ablaze]

Sorry, but bump.

[TheGreyGhost]

Hi

 

The math usually uses sin and cos because this gives nice "smooth" animations instead of jerky changes in direction, a bit like a swinging pendulum.  It's hard to explain this in a few lines, this link might give you a bit of an idea about how sine and cosine make the motions "smooth", but to really properly understand it you probably need to study up a bit on trigonometry.

 

http://www2.seminolestate.edu/lvosbury/SineCosine.htm

 

An example from the ocelot code:

 

                this.ocelotBackLeftLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F) * 1.0F * maximumSwingAngle;
                this.ocelotBackRightLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F + 0.3F) * 1.0F * maximumSwingAngle;
                this.ocelotFrontLeftLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F + (float)Math.PI + 0.3F) * 1.0F * maximumSwingAngle;
                this.ocelotFrontRightLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F + (float)Math.PI) * 1.0F * maximumSwingAngle;
                this.ocelotTail2.rotateAngleX = 1.7278761F + ((float)Math.PI / 10F) * MathHelper.cos(animationTime) * maximumSwingAngle;
                this.ocelotTail2.rotateAngleX = 1.7278761F + ((float)Math.PI / 10F) * MathHelper.cos(par1) * par2;

 

If we just look at the backleftleg - we are changing the rotation angle around the x axis, which is the side of the ocelot, so the leg is swinging forwards and backwards.

If you have the function

angle = cos(animationTime)

it converts the animationTime into an angle

For example if animationTime is in seconds:

when animationTime is 0, cos(0) = 1 so the angle is set to 1.

animationTime increases a bit, say to about 0.5.  cos(0.5) is about 0.87, so the angle is set to 0.87

at 1 second, cos(1) = 0.54

at 1.5 seconds, cos(1.5) is approximately 0

at 2 seconds, cos (2) is approximately -0.4

And if you keep increasing the time, you'll find that the cos() oscillates smoothly between +1 and -1 in a repeating cycle.  So you've converted your animationTime in seconds into a smoothly swinging angle back and forth.  Every 6.3 seconds or so, the animation repeats (the exact number is 2 * Math.PI).

There are a couple of extra tricks - if you want the animation to move faster or slower, you multiply the animationTime by a larger or smaller number.

If you want the angle to swing by larger amounts, you multiply the cos by a larger number.

If you've got two animations and you want to delay one of them a bit (i.e. one of the legs swings ahead of the other one) you add a delay time to your animation time

So in the ocelot example,

this.ocelotFrontLeftLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F + (float)Math.PI + 0.3F) * 1.0F * maximumSwingAngle;

we are slowing down the animation a bit

(* 0.6662F)

and we are delaying it a bit

Math.PI + 0.3F

and we are making the leg swing more

(* maximumSwingAngle).

 

Choosing the correct values is pretty much a matter of trial and error, with some hints based on vanilla code.  If you're animating something similar to a vanilla creature, I'd suggest you look at the values it uses to get a good starting point.

 

-TGG

[Ablaze]

Hi

 

The math usually uses sin and cos because this gives nice "smooth" animations instead of jerky changes in direction, a bit like a swinging pendulum.  It's hard to explain this in a few lines, this link might give you a bit of an idea about how sine and cosine make the motions "smooth", but to really properly understand it you probably need to study up a bit on trigonometry.

 

http://www2.seminolestate.edu/lvosbury/SineCosine.htm

 

An example from the ocelot code:

 

                this.ocelotBackLeftLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F) * 1.0F * maximumSwingAngle;
                this.ocelotBackRightLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F + 0.3F) * 1.0F * maximumSwingAngle;
                this.ocelotFrontLeftLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F + (float)Math.PI + 0.3F) * 1.0F * maximumSwingAngle;
                this.ocelotFrontRightLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F + (float)Math.PI) * 1.0F * maximumSwingAngle;
                this.ocelotTail2.rotateAngleX = 1.7278761F + ((float)Math.PI / 10F) * MathHelper.cos(animationTime) * maximumSwingAngle;
                this.ocelotTail2.rotateAngleX = 1.7278761F + ((float)Math.PI / 10F) * MathHelper.cos(par1) * par2;

 

If we just look at the backleftleg - we are changing the rotation angle around the x axis, which is the side of the ocelot, so the leg is swinging forwards and backwards.

If you have the function

angle = cos(animationTime)

it converts the animationTime into an angle

For example if animationTime is in seconds:

when animationTime is 0, cos(0) = 1 so the angle is set to 1.

animationTime increases a bit, say to about 0.5.  cos(0.5) is about 0.87, so the angle is set to 0.87

at 1 second, cos(1) = 0.54

at 1.5 seconds, cos(1.5) is approximately 0

at 2 seconds, cos (2) is approximately -0.4

And if you keep increasing the time, you'll find that the cos() oscillates smoothly between +1 and -1 in a repeating cycle.  So you've converted your animationTime in seconds into a smoothly swinging angle back and forth.  Every 6.3 seconds or so, the animation repeats (the exact number is 2 * Math.PI).

There are a couple of extra tricks - if you want the animation to move faster or slower, you multiply the animationTime by a larger or smaller number.

If you want the angle to swing by larger amounts, you multiply the cos by a larger number.

If you've got two animations and you want to delay one of them a bit (i.e. one of the legs swings ahead of the other one) you add a delay time to your animation time

So in the ocelot example,

this.ocelotFrontLeftLeg.rotateAngleX = MathHelper.cos(animationTime * 0.6662F + (float)Math.PI + 0.3F) * 1.0F * maximumSwingAngle;

we are slowing down the animation a bit

(* 0.6662F)

and we are delaying it a bit

Math.PI + 0.3F

and we are making the leg swing more

(* maximumSwingAngle).

 

Choosing the correct values is pretty much a matter of trial and error, with some hints based on vanilla code.  If you're animating something similar to a vanilla creature, I'd suggest you look at the values it uses to get a good starting point.

 

-TGG

 

Alright, I'll keep this in mind while making a mob. I wanted to make a "Bookworm" boss mob, which spawns in my "Book" dimension. So I wanted those sway kind of motions, similar to a snake or a worm.