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Tips for skew shaped and images?


proyb2
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You can use matrix transforms to apply skew to objects. It's not straightforward, and it's not well-documented, but it's possible. Every display object has a property called "worldTransform", which is a local transformation matrix that's applied at render time. All the positioning, rotating and scaling Phaser does to objects is internally calculated into that matrix. It's possible to add skew to it, look up affine transformation matrices :)

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I suggest you try this (it has worked for me, although it is in all probability still buggy in certain cases, and since the sin/cos aren't cached it's going to be a little slower. But hey :)

 

1. Extend your object that you want to skew

2. Give it skewX and skewY properties.

3. Create a function for your extended prototype called "updateTransform"

4. Go into the phaser source code and copy the content of PIXI.DisplayObject.prototype.updateTransform into your overriding updateTransform

5. Replace the following lines:

        a  =  this._cr * this.scale.x;        b  =  this._sr * this.scale.x;        c  = -this._sr * this.scale.y;        d  =  this._cr * this.scale.y;

With this:

        a  =  this.scale.x * Math.cos(this.rotation + this.skewY);        b  =  this.scale.x * Math.sin(this.rotation + this.skewY);        c  =  this.scale.y * Math.sin(-this.rotation - this.skewX);        d  =  this.scale.y * Math.cos(this.rotation + this.skewX);

6. comment out the rotation cache calculation

7. amend the if clause "if (this.rotation % PIXI.PI_2)" to say "if (this.rotation % PIXI.PI_2 || this.skewX || this.skewY)"
 
Now you have objects with Flash-compatible skewX and skewY values (ie skewX and skewY are radians values of skew angles). 

 

At least that's how it works for me (top sprite's texture is circular):

 

fugw8u1.png

 

 

If you want ALL DisplayObjects to have skew, you can try and override the function you copied from (PIXI.DisplayObject.prototype.updateTransform). In that case, I suggest you add checks for whether skewX and skewY exist, or otherwise make sure they are added in the constructor. I have not tested this and I cannot guarantee it'll work.

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On 6/24/2015 at 2:16 AM, wayfinder said:

I suggest you try this (it has worked for me, although it is in all probability still buggy in certain cases, and since the sin/cos aren't cached it's going to be a little slower. But hey :)

 

1. Extend your object that you want to skew

2. Give it skewX and skewY properties.

3. Create a function for your extended prototype called "updateTransform"

4. Go into the phaser source code and copy the content of PIXI.DisplayObject.prototype.updateTransform into your overriding updateTransform

5. Replace the following lines:


        a  =  this._cr * this.scale.x;        b  =  this._sr * this.scale.x;        c  = -this._sr * this.scale.y;        d  =  this._cr * this.scale.y;

With this:


        a  =  this.scale.x * Math.cos(this.rotation + this.skewY);        b  =  this.scale.x * Math.sin(this.rotation + this.skewY);        c  =  this.scale.y * Math.sin(-this.rotation - this.skewX);        d  =  this.scale.y * Math.cos(this.rotation + this.skewX);

6. comment out the rotation cache calculation

7. amend the if clause "if (this.rotation % PIXI.PI_2)" to say "if (this.rotation % PIXI.PI_2 || this.skewX || this.skewY)"
 
Now you have objects with Flash-compatible skewX and skewY values (ie skewX and skewY are radians values of skew angles). 

 

At least that's how it works for me (top sprite's texture is circular):

 

fugw8u1.png

 

 

If you want ALL DisplayObjects to have skew, you can try and override the function you copied from (PIXI.DisplayObject.prototype.updateTransform). In that case, I suggest you add checks for whether skewX and skewY exist, or otherwise make sure they are added in the constructor. I have not tested this and I cannot guarantee it'll work.

if possible give us your source code it would be better to understand.

 

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