In Neverwinter Nights Model Shadows are done on placeables, creatures, items and tiles. Only Trimesh nodes in a model can cast a shadow.

Shadows are Stencil shadows and thus reasonably simple - but can go wrong when a complex trismesh node is used to define the shadow mesh to use. This is why many even base game models either show no shadows (the model has them turned off) or have really odd shadows at certain angles or distances (the mesh used to generate them is not perfect or too complex).

Introduction

The contents of this page handle general informations about model shadows, how to implement a model with shadows as a custom .mdl into your module - and solutions for issues that might (and probably will) come along the way. If you happen to encounter a problem that can't be solved with any of the solutions below, you can always ask around in the community and the discord. Note that the given solutions might not apply to your specific problem. If the bug perists, or if you find a way around it, by all means, do share it with us to keep the flame alive.

It goes with saying that you have a backup of your file before you head out to edit or export it, therefore the author of this page takes no responsibility if data gets lost along the way.

Shadows

Definition

What are shadows essentially? This question might be irritating to some and feel like it's actually easy to answer.
However, as with anything, the case if often more complex as explained the quote down below:

Shadows are a result of the absence of light due to occlusion ^{(occlusion: blocking off, blockage)}. When a light source's light rays do not hit an object because it gets occluded by some other object, the object is in shadow. Shadows add a great deal of realism to a lit scene and make it easier for a viewer to observe spatial relationships between objects. They give a greater sense of depth to our scene and objects. [...] 

Shadows are a bit tricky to implement though, specifically because in current real-time (rasterized graphics) research a perfect shadow algorithm hasn't been developed yet. ^{Taken from LearnOpenGL, click here to learn more (Note: Neverwinter uses OpenGL)}

Shadow Mapping

The concept of shadow mapping is quite simple. All you need is a light source for your environment and a scene it interacts with. To demonstrate this, let's say the ground there in our image is a single tile of our area and the cube is an object in it's way - for example a crate.

The light source is constantly lighting up the space around itself where it is placed in our environment. This is described in many shapes, sometimes as a cone (car lights), sometimes a sphere (torch or light bulb) and other times it's the sun. What is important though, is that once the light hits the object in it's way, it will describe the rest of it's path as occluded, thus rendering the faces it can not physically reach as dark. The game uses basic Stencil Shadows and does not use shadow mapping or advanced modern shadow techniques.

Working with Shadows

Prerequisites

Neverblender Step-By-Step Tutorial

Step 1 - Loading Up your File:

Load up your project file (after having created a backup file for it.) For this tutorial I will load up one of my recent head models. To learn how to extract models as a readable MDL ASCII file, click here. Or one of the links for more information on UV Mapping or Texture Painting in general.

For my example, I have taken pfh0_head155, remodelled it, renamed it to pfh0_head200 and did the same for it's pfh0_head200g. You may notice that my mesh has more polygons than the average head model for a NWN character. How you choose to model your head is up to you, enjoy the freedom.

Keep in mind for the future: p = part-based, f / m = female / male, h = human, 0 = Phenotype Normal, head = model attached to head node, 200 = ID, g = geometry. A model can not be loaded in the Creature Wizard with no geometry.

The hierachy goes as follows:

_{|pfh0_head200 (PARENT: root of your head, it should be centered and rotated to x0.0, y0.0, z0.0, scaled to 1.0)
|→ pfh0_head200g (CHILD TO pfh0_head200 | PARENT OF pfh0_head200g: this is your head model.)
|→→ pfh0_head200g (CHILD TO pfh0_head200g | PARENT OF image_textures: These are the data properties of your model)
|→→→ image_texture (CHILD TO pfh0_head200g: The material that will be laid over your texture.)
|→→ Vertex Groups (CHILD TO pfh0_head200g | PARENT TO constraints: This is your vertex group 'folder')
|→→→ constraints (CHILD TO Vertex Groups: Vertex Groups are used for dangly mesh weight assignment.)
| |
|→ shadow_dummy (CHILD TO pfh0_head200: This is a hidden mesh. You will learn about it later.)
|→→ shadow_dummy (CHILD TO shadow_dummy: Data property of the shadow dummy mesh
|→→→ material (CHILD TO shadow_dummy: unused material generated by the export.)}

Step 2 - Checking your properties:

Your root should be an empty plain axes and have the classification set to Character, the Supermodel as null and the animation scale to 1 in your object properties. Character describes the root of your model to be of the type Character, which is essential for character models to load up correctly. make sure to name it properly.

You can give it entirely different names, too, but for the purpose of this tutorial we won't do that as this is also an entirely different topic.

Next, your head model should be parented to your root (CTRL+P → Set Parent → Object). Make sure the head of your model's neck (the center between the end corners of your jaw) is perfectly! centered to the middle of your root where the two straight lines cross. This is the point where the head bottom 'attaches' to the neck phenotype's top.

Check your object properties once more: Aurora Base Properties → Classification →  Character & Supermodel → null & Animation Scale → 1.00. ^{This part is unnecessary if you've parented it before, so double check if the model was parented correctly and the settings are the same.}
We will ignore image_textures, vertex groups and the shadow dummy + it's material for now.

My Properties Checklist

• My Root is an Empty Plain Axes
• My Model is Parented to the Root and now a Child of it
• I have a material for my model.
• (Optional, Danglymesh:) My constraints for the Vertex Group are weight painted for Danglymesh
• (Aurora Base Properties) I have set Classification to: Character
• (Aurora Base Properties) I have set Supermodel to null
• (Aurora Base Properties) I have set Animation Scale to 1.00

To finish this all up, we will now also add an additional property for our head model which the root does not have as an visible option. In your Object Properties, scroll further down until you see the Aurora Mesh Properties. This is our most vital tab. It has just a few ticks, a a few sliders and checkmark options. To learn more about it, go here.

Danglymesh

If you are using a danglymesh like me, set your type to Danglymesh and make sure to paint your assigned vertexes accordingly, like the danglymesh tutorial above suggests. What period, Tightness and Displacement you use, is your preference for the kind of dangly material you're working with. Triangulate the Faces like described in the Trimeshes below.

Trimesh

If it's just a static mesh, set it to Trimesh. Trimesh. Now what does that mean? Triangulated Mesh. Have you triangulated your faces yet? Do it now. Edit Mode → Search → Triangulate Faces (Or just CTRL+F and Dropdown to the option).

Now that your model is finally ready to be exported, we are now entering the part that's important for the shadows to work ... behold.

Step 3 - Going Dark:

To export our model with a shadow, check the Shadow Checkbox below the Render Checkbox. This will, as we have learned with Shadow Mapping above, make the Object's faces which meet the ray of light be lit while the back creates a shadow map over the surface the angle of the light source is pointing to and therefore occludes the light on the other side of the model and the passing light ray onto the ground/wall/surface.

Now export your mesh as an .MDL, open up NWHak, update your .hak file, open up the Toolset and your module that contains your custom content .hak file and take a look.

Great! It works! Perfectly. ... Or does it?

Don't panic. While I'm not really sure why this happens, this usually happens to models with a higher polygon count. I assume that some vertices might stretch out to the shadow map, but that's just blind guessing at this point. Instead. Let's find a solution in the bug category down below.

Buddha's Edit: How about we get to the source of this once and for all?! See the next section. Also, thanks to Symmetric for the Blender methods!

Shadow Tearing, Stretching, or Ripping Bugs - Causes and Fixes

The Cause of Shadow Tearing

There are many hypotheses on what causes stretched shadows, or ripped shadows, or shadow tearing. Pick your term, it’s when a long spike of shadow extends from a model to the ground as pictured above. The actual cause as determined by testing is what we’ll term Multiple Edges, as that is the term used in 3ds Max and it best sums it up. Multiple Edges is when more than 2 faces share the same edge. Note that this isn't two overlapping edges – it is 3 or more faces sharing the same edge defined by the same 2 vertices.

The Causes of Multiple Edges

Why is it so common? What is it about our work or processes that leads to multiple edges? After much reading, it seems the most likely culprits are:

• Depthless extrusions -- selecting an edge and accidentally extruding it a distance of 0 by either improperly canceling the operation or applying it and not properly canceling the tool.
• Edge extrusion -- Selecting an edge that is already shared by 2 faces and extruding it intentionally.
• Vertex welding -- Intentionally or unintentionally snapping vertices or edges from more than 2 faces to the same points, then welding them; or selecting all vertices and welding without realizing there were two overlapping edges.
• Flipped normals -- selecting the face of a watertight mesh and flipping the normals causes an edge adjacent to a non-flipped poly to be seen as a multiple edge by 3ds Max’s xView and likely by other renderers.

Mythbusting

“Pointy bits cause shadow tearing!” – almost true. What actually happens is that to get a pointed face, like say on the c_owlbear.mdl, modelers will grab an edge, extract it, then target weld the two corner verts to make a triangle. That leads to multiple edges at the base of that new triangle.

“Overlapping faces cause shadow tearing!” – No, actually they don’t, BUT – typically an overlapping face is geometry that is attached to the main mesh and folded back or a face that has been duplicated and left in place. Because of that the attachment edge or edges of that face generate multiple edges with other mesh geometry.

“Flipped normals cause shadow tearing!” – TRUE…but this is a weird edge case (see what I did there?) where renderers consider the edge adjoining a flipped face as a multiple edge.

Let’s Prove It

Breaking it down to the simplest problem, we’ll need 3 triangles – so let’s make Finhead Guy. We’ll make him out of 3 one-side triangles, each with their own texture.

Notice that they all come to evil points, which is one of the mythical reasons for things to have shadow tearing. For now, we’ll leave them all as separate meshes, each with shadows turned on. How does this look in game then?

Even though these are “pointy bits” they don’t cause any shadow tearing. They’re three separate meshes now, so let’s attach them all into one big mesh to see if that changes anything. We won’t weld any vertices though, so they’ll still be 3 distinct faces that don’t share any geometry, not even one vertex:

Still no shadow tearing. But then we discover that the top fin is only visible from one side.

We’ll just duplicate it and flip the normal! Keep in mind that we’ve still not welded any vertices so all 4 triangles are still distinct geometry. Two of them share the exact same space though now and are overlapping faces.

Still no tearing. So pointy bits didn’t cause tearing. Overlapping faces didn’t cause tearing. What happens if we finally weld the vertices at that center edge, joining all 4 of our triangles? It looks the same in the modeling program afterwards, and you can even see both sides of the top fin, but in game…

What has happened?! The answer is clearly that 4 faces now share a common edge, that 4 is greater than 2, and we now have shadow tears. Just to be sure, let’s reduce it to the minimum possible problem from our hypothesis and delete that 4^th triangle we added to make the fin two sided. Now we’re down to 3 simple triangles joined along the center seam.

The tearing is still there. Even worse, notice that from the side where you can see the top fin (view facing the normal) there is now a cut out in the torso and arm shadow on the ground caused by the inverse shadow tear from the multiple edges.

The Fix for Shadow Tearing using Blender

How to FIND Multiple Edges in Blender

• Select => All By Trait => Non Manifold" with the "Multiple Faces" setting will give you the edge directly.

How to FIX Multiple Edges in Blender

• With the multiple edges still selected from the previous step to Find them, select Mesh => Split => Faces by Edges.
• Then re-pivot using Object => Set Origin => Origin to Center of Mass.

• Export your model.

The Fix for Shadow Tearing using 3ds Max

How to FIND Multiple Edges in 3ds Max

• With the mesh selected, in the Perspective View click Smooth + Highlight => xView => Multiple Edges. This will highlight any multiple edges in bright green.

How to FIX Multiple Edges in 3ds Max

3ds Max has an Editable Poly mode, and because that mode automatically fixes any multiple edge errors by splitting the edge you can just do a quick conversion to clear it. In 3ds Max, the quickest way to fix it is as follows:

• Select the mesh with the multiple edges
• In the stack, select the Editable Mesh

• From the modifier list, add Edit Poly to the stack

• Right click on Edit Poly and select Collapse To, hitting Yes at the prompt.

• With Editable Poly selected, from the modifier list, add Edit Mesh to the stack

• Right click on Edit Mesh and select Collapse To, hitting Yes at the prompt.

• Select your mesh and use the ResetXForm button with Safe Pivots checked on the NWmax+ Mesh Tools rollout.

• Export your model.

Bug Reports and Solutions