Tutorial: Introduction to UDMF Vertex Slopes

Jan 15, 2018Tutorial

Vertex Slopes Are Powerful and Easy

So what are vertex slopes? The name is quite self-explanatory – as the name describes, these are slopes controlled by the vertexes.

If you have had any experience in 3D modelling you’ll know everything can be made with triangles – fortunately the same concept applies here. We’ll start off by drawing a series of triangular sectors. These can be any dimension, they can be any ‘type of triangle’, as long as it’s 3 sided (that is, the sectors you want to slope only ever have 3 vertices.

For simplicity’s sake while learning, I’d create a grid of triangles as seen below. Once done you’ll have created a ‘mesh’ of sorts. You can now control the heights of each vertex, which in many ways is similar to how ‘proper terrain’ is done in 3D modelling!

So you’ve set up your grid of triangular sectors, opened the 3D editor mode and wait… What’s this? Some weird blue handles have appeared! These handles are what control vertex slopes. You should now see something similar to the below:

You can select them with left mouse click, and using the mousewheel you can control their vertical height. In addition to this you can select multiple vertex slope handles and control them at the same time! – See demonstration below.

As you can see the whole effect is easy to use! It can become difficult when you’re trying to draw additional geometry around it, such as bridges or ceiling lights etc, but that’s all part of the fun of mapping.

Check out the below cavernous areas I’ve made to see some examples of what can be achieved using this technique.

Considerations When Using Vertex Slopes

  • As awesome as these slopes are, try to be careful with them – they greatly increase the sector count and because of such a large number of them will make the game lag a lot on lower end machines.
  • In addition to this, floor slopes can be awful, as it makes the movement for the player become bumpy and/or slippery, making the gameplay take a negative hit.
  • Try to care for the textures used on your slopes. By default the texture will stretch with the slope’s shape – the greater the angle the more the texture warps. To beat this, you can use “texture scaling” in the sector options to manually adjust, but this can get very tricky and time consuming.
  • Try to leave the vertex slopes until the very end of a map. If you decide later on you want to add additional features in the area you’ve ‘sloped up’ you may find it both time consuming and tedious.

Tutorial Difficulty:

Required Tools & Resources

  • GZDoom Builder
  • Only 10 minutes of your time

Any Issues?

If the blue vertex handles are missing don’t despair! Assuming you’re using the correct tools (GZDoom Builder, UDMF map format) it might be the case that you just need to turn them on. The shortcut is Alt-V to turn on this feature specifically. You also need to ensure the ‘true 3D mode’ is enabled, which is simply done by pressing TAB when in 3D mode.

Another thing to double check is that your sectors are indeed three sided, with only 3 vertices. If there are vertex handles they don’t appear but you thought they would, it may be because the sector has more than three sides. Make sure when you begin creating your triangular sectors you do it logically. Don’t just start drawing random lines everywhere as it can become a game of chasing your own tail to limit everything to three sides without ending up with a million tiny sectors. Also make sure that the offending sector(s) aren’t joined with other sectors.

Rarely the blue vertex handles don’t appear on certain vertexes for no discernable reason. If this happens, return to the 3D view, select the vertex in Vertex Mode, right click to edit, and manually change the offset. As soon as you do (and if it’s a proper triangular sector) the slope and the blue handle will appear as it should in 3D view.

Happy Mapping!

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