So, you've probably seen examples where some DOM elements are rotated on the X/Y/Z axis. This is nothing new as the transform property was introduced a relatively long time ago.
CSS transforms give us the capability to rotate, scale, skew, and translate our elements, The possibilities are endless. But one of the least known properties related to CSS transforms is the perspective property.
perspective basically turns the "space" in which the object is contained into a 3D plane, or as we already know a three-dimensional Cartesian coordinate system (the same X/Y/Z system we use to rotate/scale/skew/translate our elements if we're using all three planes or at least the Z plane). We can see the effects of the perspective property in this pen:
Notice a few things:
- The perspective property is applied to the parent of the children that we want to be three-dimensional. Meaning that its main difference with transform's own perspective() function (yes, the transform property also has possible value which is said function) is that it applies the 3D Cartesian coordinate system to ALL of it descendants, while the perspective() function only applies the previously named coordinate system to the element.
- The higher the value of our perspective property the closer we get to the element, meaning that whatever transformation we apply to it may be more noticeable if we set a small value. This is better seen when applying rotational transforms to our elements.
- We specified a value for our element's transform-origin property. Isn't this a bit confusing keeping in mind that now we have our parent's perspective property tampering our transformed elements? If you were asking yourself that, then you're correct, and we'll talk a bit more about it below.
As you may have probably guessed, the perspective property has a companion which is the, drum roll please, perspective-origin property. The perspective-origin property is the one in charge to set where our vanishing point is, or to put it simply it determines from what angle we're looking at our elements. In the pen below, we can see our previous example usage of the perspective property in combination with the perspective-origin property, on the left the value is set to center left and on the right the value is set to center right.
If we wanted to, we could get rid of both element's own transform-origin value (set it back to 50% 50%) and work with the parent's perspective-origin to achieve the same results as in the first pen, but for demonstrational reasons we're using both transform-origin and perspective-origin properties in this last pen.
Note: the perspective property isn't a shorthand that includes our previously mentioned perspective-origin property, they both have to be declared separately when writing our CSS.
Finally, let's add another layer of complexity to the beloved CSS 3D space we're currently working on. If we're working with transformations on the Z plane (most likely stacking content on different levels) and you rotate the element on it's Y axis, you may notice that all of sudden you have no layers and everything seems... flat. That is because our CSS transform-style property is set to a flat value by default. This property basically defines if children elements are in a 3D space or a 2D space, and it has 2 possible values flat and preserve-3d, both are pretty self-explanatory. On the pen below, created by Louis Lazaris, we can check the transform-style property in action.