DM-Planetoid

Overview

Screenshots

Installation

The building of this map

The geometry

Building this map I ran into a lot geometry problems. The feared BSP hole and the terrifying Hall Of Mirrors (HOM). This is due to two aspects.

The BSP Problem

Building this map I ran into a lot of BSP holes. The main way to control this is to minimise the BSP cuts. In this geometry most walls are aligned so to minimise the BSP cuts. The way to do this is make sure every angle is the same. Choose a fixed ratio for the diagonal walls and the non-perpendicular walls.
I had to align the walls exactly. When two pieces of wall are not exactly aligned, the number of BSP cuts doubled.
Another important note about BSP is that although people say Non-solids and Semi-solids do not affect BSP, I experienced otherwise. After reaching a stable geometry with working ZonePortals I couldn't add Non-Solid or semisolid decorations without collapsing the geometry somewhere.
Another BSP problem is caused by having some area's too close to eachother. This will cause a BSP overspill into the adjacent areas. The four main areas are located as far from eachother as possible, and are exactly opposite. This reduces the number BSP cuts. Sometimes the geometry collapsed just by moving an area a little bit.
In one of my attempts I tried to isolate the areas by intervening walls, but this was not effective.

The ZonePortal Problem

This map contains :

• 6 zoneportal sets in a doorway
• 6 zoneportals at the edge with in intermediat zone.
  You can stand on the edge of the planetoid

• Most tutorials tell you about perpendicular Zoneportals.
  The zoneporatal and the area behind it must have the same geometry at both ends. When using non-perpendicular Zoneportals I found out that that both the horizontal and the vertical angle of both ends of the Zoneportal must be identical. If not, the portal will work, but give rise to misalignment. You can see through it, walk through it, but you'll end up at the wrong place. This was problematic in the case of the stairs connecting the buildings.
• Keep all zoneportals on the same level.
  Height differences cause a visual bump and lag when walking through it.
• Don't put zoneportals is such a way that you can look back on yourself
  This will cause a HOM.
• The zoneportals are sensitive to BSP cuts.
  Too many BSP cuts and you end up with Holes in the zoneportal, resulting in a HOM. This is linked to the triangular geometry of this map made it difficult to reach a stable geometry.

The brush order problem

Both the geometry (BSP holes) and ZonePortals (HOM) problems are closely related to the brush ordering.
The order of brushes in the map are :

1. Main area subtractive brushes.
2. Additive brushes
3. Subtractive brushes
4. Semi-solid brushes.
5. Non-solid brushes including portals.

The skybox

There is no skybox. I abandoned the skybox idea for the following reasons.

• Adding the geometry for the skybox sometimes caused the geometry to collapse because of BSP overspill.
• In some attempts the Skybox caused nasty HOM's.
• The framerate is low as it is. Adding a skybox would only make it worse.

Decorating the map

When I finally got a stable geometry, I began decorating the map. But when I added Non-Solid or semi-solid brushes the geometry collapsed. It would have been nice to have decorations like vines, some ledges for items,etc. As a workaround I edited some textures and put them on the Plate and Bench decoration actors. All FireObjects (the flameholders) are off, far too many particle systems resulting in loss of framerate.

Lighting

Due to the non-vertical walls of the tetrahedron, I had to resort to ZoneLighting. Using normal lights, I kept having pieces of wall which weren't lighted. I added a corona with animated fire for most lights because particlesystem fires slowed down the map and adding non-solid fire brushes collapsed the geometry.

All lights use no light effect although most lights are Fires. Using the LE_TorchWaver light effect slowed down the map.

Tips and lessons learned

• Don't.
  This kind of map takes lots of time. It's a frustrating proces of trial, error, and starting over from scratch. And finally, others will look in amazement, but probably never play a map like this
• First make the Zoneportal architecture.
  Keep in mind that the zoneportal geometry must be exactly identical at both ends.
• Keep the areas as far apart as possible.
  The BSP overspill can cause collapse of the geometry.
• Build the geometry crossing the zoneportals, like the stairs, first.
  Getting these alligned properly is problematic but nessecarry for a good result. If you get this wrong, you can fall 'inbetween' the stairs
• Slowly add the rest of the geometry.
  Keep the portals working. When I had a large part of the geometry ready, I used brush intersection to fix it.
• Use fixed ratio for angles
  If the desired geometry contains non-perpendicular pieces, choose a fixed ratio for them.
• Regularry check for BSP Holes & HOM's
  Walk through the entire map to check for BSP holes and HOM's. BSP hole sometimes these occurred at specific locations. The zoneporatals need thorough checking. Sometimes a portal seems to work from one end, but not the otherway around.

Dedication:

• M.C.Esher for the inspiration.
• Einsturzend Neubauten (guess why)

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