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ItemCannon fixes #1018

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ItemCannon fixes #1018

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aa79973
Changed where ItemCannon spawns fired item
Sep 5, 2020
7381d51
Fixed ItemCannon bug where air resistance was effecting projectiles
Sep 5, 2020
c195438
Cleaned up ItemCannon code a bit
Sep 12, 2020
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62 changes: 7 additions & 55 deletions src/main/java/openblocks/common/entity/EntityItemProjectile.java
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Original file line number Diff line number Diff line change
Expand Up @@ -39,64 +39,16 @@ public static void registerFixes(DataFixer fixer) {

@Override
public void onUpdate() {
final double x = posX;
final double y = posY;
final double z = posZ;

final double vx = motionX;
final double vy = motionY;
final double vz = motionZ;

// let vanilla run
super.onUpdate();
if (!isDead) return;
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It was supposed to be isDead, then whole thing becomes more sensible.

Basically, purpose of this code was to let super.onUpdate handle all state changes, then overwrite movement with our own. Restoring just motion before update leads to numerical errors, which would cause mismatch with canon targeting algorithm (not that it was super precise in first place though).

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Yea, although with isDead instead it was double-moving the item, so that would have to get fixed too. It's basically a choice between the way I've got it, which is a a bit of a hack no doubt, and duplicating half the code inside EntityItem.onUpdate. If you'd prefer it the other way, that's fine by me. I wouldn't worry about the numerical errors though--these values are all doubles pretty close to 1, so back-of-the-envelope calculation says worst case is an acceleration of about 4.5e-15 blocks/s^2.

// and then overwrite position calculations

this.posX = x;
this.posY = y;
this.posZ = z;

this.motionX = vx;
this.motionY = vy;
this.motionZ = vz;

this.prevPosX = this.posX;
this.prevPosY = this.posY;
this.prevPosZ = this.posZ;
this.motionY -= 0.03999999910593033D;

move(MoverType.SELF, this.motionX, this.motionY, this.motionZ);

boolean hasMoved = (int)this.prevPosX != (int)this.posX || (int)this.prevPosY != (int)this.posY || (int)this.prevPosZ != (int)this.posZ;

if (hasMoved || this.ticksExisted % 25 == 0) {
if (this.world.getBlockState(new BlockPos(this)).getMaterial() == Material.LAVA) {
this.motionY = 0.20000000298023224D;
this.motionX = (this.rand.nextFloat() - this.rand.nextFloat()) * 0.2F;
this.motionZ = (this.rand.nextFloat() - this.rand.nextFloat()) * 0.2F;
playSound(SoundEvents.ENTITY_GENERIC_BURN, 0.4F, 2.0F + this.rand.nextFloat() * 0.4F);
}
// Remove the air drag that EntityItem.onUpdate adds to our velocity
if (!this.onGround) {
double f = 0.98F;
this.motionX = this.motionX / f;
this.motionY = this.motionY / f;
this.motionZ = this.motionZ / f;
}

// Zero Air Friction
float f = 1F;

// Keep ground friction
if (this.onGround) {
BlockPos underPos = new BlockPos(MathHelper.floor(this.posX), MathHelper.floor(getEntityBoundingBox().minY) - 1, MathHelper.floor(this.posZ));
IBlockState underState = this.world.getBlockState(underPos);
f = underState.getBlock().getSlipperiness(underState, this.world, underPos, this) * 0.98F;
}

this.motionX *= f;
// Y would there be Y resistance :D
// ^ not my pun, I'm just porting :P, ~B
// motionY *= 0.98;
this.motionZ *= f;

if (this.onGround) this.motionY *= -0.5D;

handleWaterMovement();
}

}
}
11 changes: 10 additions & 1 deletion src/main/java/openblocks/common/tileentity/TileEntityCannon.java
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Original file line number Diff line number Diff line change
Expand Up @@ -127,8 +127,17 @@ private void fireStack(@Nonnull ItemStack stack) {
final ITriggerable rpc = createServerRpcProxy(ITriggerable.class);
rpc.trigger();

// spawn the item approximately at the end of the barrel
double yawr = Math.toRadians(currentYaw);
double pitchr = Math.toRadians(currentPitch);
double barrelLength = 0.5;
double barrelBaseHeight = 0.3;
double x = pos.getX() + 0.5 - Math.sin(yawr) * Math.cos(pitchr) * barrelLength;
double y = pos.getY() + barrelBaseHeight + Math.sin(pitchr) * barrelLength;
double z = pos.getZ() + 0.5 + Math.cos(yawr) * Math.cos(pitchr) * barrelLength;

// projectileOrigin is not used here, it's used for the calculations below.
EntityItem item = new EntityItemProjectile(world, pos.getX() + 0.5, pos.getY(), pos.getZ(), stack);
EntityItem item = new EntityItemProjectile(world, x, y, z, stack);
item.setDefaultPickupDelay();

// Now that we generate vectors instead of eular angles, this should be revised.
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