Making a perspective grid

[Espermaschine]

Coming from this thread:
http://www.gimp-forum.net/Thread-80ies-c...435#pid435

There are several problems with making a perspective grid:
1. for a real perspective you'd have to set up a horizonline and a vanishing point, right ?
2. Also for a real perspective grid, the horizontal lines would need to get closer, the more distant they are.

The perspective tool in Gimp is not a real perspective tool. It doesnt follow any perspective rules, unlike Inkscape's perspective extension or LPE.
Gimp's perspective tool is just a sort of free transform.

So lets say we throw that out of the window and make a fake perspective grid instead.

Im using a 640x400px canvas and with ofnuts' Path-grid plug-in, i set up a grid 36x36px.
I also set up guides around the edges of my canvas, and at 50% horizontally.

   

Heres the first problem:
i cant put guides outside the canvas, which i need as guidance and for snapping. If i want to stretch out the grid at the bottom, i have to extend the canvassize.
The perspective tool doesnt seem to give me any help with the coordinates.

So im setting up two additional guides 200px away from the edges of my original canvas after i extended my canvas.

   

Next problem: when i use the perspective tool in path mode, its applied to the whole canvas.
Im fixing that by alpha selecting my original canvas size.

   

After i applied the fake perspective to my path grid, i stroke the path on a new transparent layer.

   

Comments ?

[Ofnuts]

Trick: sometimes it can be easier to

• create a temporary layer, smaller that the image (for instance, encompassing the useful part of the path)
  
• optionally stroke the path on that layer
  
• click the "link" icon on both the layer and the path
  
• apply the transform on the layer
  
• let Gimp automatically apply the same transform on the path
  

[Espermaschine]

(11-07-2016, 10:53 PM)Ofnuts Wrote: Trick: sometimes it can be easier to

[list

Tried it, but why is it easier ?

[Ofnuts]

Because the handles (that are in the corner of the layer) are much closer to your point of interest... So you can zoom in, among other things. This of course assumes that the business part of your path is significantly smaller than the whole image (for instance, some text...).

[Espermaschine]

Ok, got it.

This leads to another question:
how do i get a perspective grid and an extruded text to have the same vanishing point ?
Because without that, its gonna look odd, right ?

[Ofnuts]

(11-07-2016, 11:50 PM)Espermaschine Wrote: Ok, got it.

This leads to another question:
how do i get a perspective grid and an extruded text to have the same vanishing point ?
Because without that, its gonna look odd, right ?

You can scale down a path until it becomes barely bigger than a pixel.

[Ofnuts]

If you don't want to go to the horizon, make one of the intermediate paths invisible,  merge visible paths and delete. You should be left with the front, the "horizon" and the new "back" one. Then redo path-inbetweener between the front path and that "back" one.

   

[Espermaschine]

Genius !

[rich2005]

Beat me to it but another example, using ofnuts plugins, path inbetweener and stroke visible paths.

The single vanishing point (vp) perspective is a bit of a special case. Usually there are 2 VP's and an object tapers to each. That is the blue cube in the overlay.

Since the text is normal to the view only one VP is used.

Initial paths to determine a start and end path, then lots of intermediate paths for the fill intermediate paths script.

It is not that much different from Inkscape extension interpolate.

   

[Espermaschine]

(11-08-2016, 09:19 AM)rich2005 Wrote: The single vanishing point (vp) perspective is a bit of a special case. Usually there are 2 VP's and an object tapers to each. That is the blue cube in the overlay.

Well with more then one VP its getting hard to pull off in Gimp, isnt it ?

I made this a while ago in IS. The perspective of the base text is perhaps the most difficult for Gimp.

Quote:It is not that much different from Inkscape extension interpolate.

With the difference that you end up with loads of nodes on each connecting path, which is problematic and annoying. To my knowledge there is no other way to get rid of them, but to delete them manually. Which takes ages.
You can also use 'Motion' which has the same problem.