I'm trying to do guiding lines that continue outside the image space, into the canvas space, to guide my perspective drawing but every time I do a pen tool, use anchor points, or the line tool, it hides the outside lines that fall into the canvas, only leaving the line parts that fall into the image portion
All pixels in Photoshop are restricted to the Canvas Size. You can't draw outside the canvas.
However, there is a way to draw outside a particular area via Artboards within Photoshop.
Set the Canvas size to as large as you want, larger than your needed drawing area.
Then select the Artboard Tool (under the Move Tool)
- And then click-drag with the tool to draw an Artboard the size of your desired image area.
You can refine the size or be more specific with the size by changing the numbers in the Control Bar across the top of the screen:
You'll then have, what is essentially a layer group in the Layers Panel titled "Artboard 1" with a layer inside it.
Anything you draw on that internal layer will be restricted to the artboard size (the red in the image below).
Anything you draw on a layer outside that artboard will be restricted to the canvas size (the blue in the image below).
This is really just the same results as if you had a layer mask applied to a layer group. But Artboards can be easier to manage (and export) than simple layer groups with masks.
While this still restricts all painting to the canvas size, this method makes the actual size of the canvas somewhat irrelevant overall. So, you can make the canvas larger if you need and the Artboard size will remain the same, or add additional artboards if needed. Then export/save artboards as individual images.
I would be remiss if I didn't at least mention using Illustrator if the goal is a great deal of vector paths in perspective. Illustrator has specific features for that.
You cannot have pixels outside the canvas area. You would have to make your canvas bigger.
If your image is larger than the canvas area and you want everything shown, you can do Image -> Reveal All. That will enlarge the canvas to show all graphics inside the document.
I would suggest you make a stroke of the final artboard size and then increase the canvas size so you can draw outside the "final artboard size" stroke. When you're done with the graphic you can then crop the graphic.