Jump to content

Found some unnecessary calculations

Recommended Posts

Not sure if here's the best place for this but since it is not a bug etc I avoided opening an issue on github :)

I stumbled upon some odd rotation code in phaser while reading https://phaser.io/tutorials/advanced-rendering-tutorial/part7

From src/pixi/renderers/webgl/utils/WebGLSpriteBatch.js
and src/pixi/display/Sprite.js

// Rotate matrix by 90 degrees
// We use precalculated values for sine and cosine of rad(90)
a = a0 * 6.123233995736766e-17 + -c0;
b = b0 * 6.123233995736766e-17 + -d0;
c = a0 + c0 * 6.123233995736766e-17;
d = b0 + d0 * 6.123233995736766e-17;

Ok. Some rotationcode with fancy precalculated values.

But: the value given in e-notation is 0.00000000000000006123233995736766 and therefore effectively zero.
Which makes sense since this was meant to be the precalculation of cos(rad(90)) - which equals exactly to zero.
I suppose the literal resulted from a rounding error when someone typed Math.cos(Math.radians(90)) into a console ;)

So a better version would be:

// Rotate matrix by 90 degrees
a = -c0;
b = -d0;
c = a0;
d = b0;

Maybe someone sees this and is willing to fix it on the side...

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Create New...