Develop Reference

How to improve merging by computing new faces in ThreeJS

I'm learning ThreeJS for 4 months, applying it into a personal project.
Yesterday, I achieved building a stronghold using most of ThreeJS geometries and some CSG tricks. The result looks fine, but I like precision and my geometry is kind of a mess (mostly after CSG subtractions).
[Question] I wonder if there's a known way to merge two geometries and replacing its old faces by new computed faces ? There is a JSFiddle to illustrate my question.
[Edit : Updated the fiddle with a fourth and a fifth mesh]
// FIGURE 1 : Basic merged geometry
var figure1 = new THREE.Geometry();
figure1.merge(box1Geometry);
figure1.merge(box2Geometry);
figure1.merge(box3Geometry);
figure1.computeFaceNormals();
figure1.computeVertexNormals();
var mesh = new THREE.Mesh(figure1, material);
scene.add(mesh);
// FIGURE 2 : Merged geometry with merged vertices
var figure2 = figure1.clone();
figure2.mergeVertices();
figure2.computeFaceNormals();
figure2.computeVertexNormals();
mesh = new THREE.Mesh(figure2, material);
// FIGURE 3 : Expected merged geometry (less faces)
var figure3 = new THREE.Geometry();
figure3`.vertices.push(
// manually create vertices here
);
figure3.faces.push(
// manually create the faces here
);
figure3.computeBoundingSphere();
figure3.computeFaceNormals();
figure3.computeVertexNormals();
mesh = new THREE.Mesh(figure3, material);
scene.add(mesh);
Three ways to get the same mesh
The first mesh on the left is a basic merged geometry composed of three boxGeometry.
The second mesh in the middle is exactly the same mesh, after calling the mergeVertices() function. It results saving 4 vertices. But faces inside the mesh are still there. It results not only in looking bad (for me), but also in issues for texturing or lighting these parts (face normals aren't where they should be).
The last mesh on the right is the mesh I would expect after merging. Look at the faces below the middle box, they only fit what they should.
The fact that it leads to texture and lighting issues (look at the JSFiddle, it lights the inner parts of the mesh) makes me think that it must be a simple and well-known way to solve this but I'm just feeling like a big noob.
This issue is directly linked with another question I'll ask if I don't find (or understand) any answer on SO (and maybe it'll help you to understand why I want to do that): Is there a way to apply a texture on this merged geometry without creating an unique material for each face of each geometry (because of the different UV mapping and mesh sizes) ? I can't imagine to do it manually for each face of my huge stronghold...
[EDIT] Writing my question, I just realized that ThreeCSG and its union() function do the trick. But I don't like the mess of vertices it creates. Even for basic geometry like these boxes, ThreeCSG will create strange vertices and faces on parts of the geometry where everything was already fine.
I updated the JSFiddle with a fourth mesh (CSG). In this simple usecase, we can see that there are 2 vertices and 2 faces more than expected. It seems that it kept the old faces (look at the wireframe !).
Is ThreeCSG union the best option for now ?
[EDIT 2] Fiddle updated with native CSG geometry. It gives the result I expected with only 20 vertices and 32 faces. Thanks to Wilt for this idea. The issue is that hard coding the polygons takes too long (take a look at the code for only three boxes). I have no JSON file to load and generate the polygons, I only have ThreeJS geometries. So I'll look at the conversion between ThreeJS and ThreeCSG geometries and I hope to understand why when there is a conversion, it gives a bad result.

How to Change a Box's dimensions/size after creation?

One can easily create a THREE.BoxGeometry where you have to pass arguments when creating as three separated arguments for width, height, and depth.
I would like to create any and all THREE[types]() with no parameters and set the values after that.
Is there a way to set the dimensions/size of the box geometry after creation (possibly buried in a Mesh already too)? other then scaling etc.
I couldn't find this in the documentation if so, otherwise maybe a major feature request if not a bug there. Any thoughts on how to classify this? maybe just a documentation change.

If you want to scale a mesh, you have two choices: scale the mesh
mesh.scale.set( x, y, z );
or scale the mesh's geometry
mesh.geometry.scale( x, y, z );
The first method modifies the mesh's matrix transform.
The second method modifies the vertices of the geometry.
Look at the source code so you understand what each scale method is doing.
three.js r.73

When you instantiate a BoxGeometry object, or any other geometry for that matter, the vertices and such buffers are created on the spot using the parameters provided. As such, it is not possible to simply change a property of the geometry and have the vertices update; the entire object must be re-instantiated.
You will need to create your geometries as you have the parameters for them available. You can however create meshes without geometries, add them to a scene, and update the mesh's geometry property once you have enough information to instantiate the object. If not that, you could also set a default value at first and then scale to reach your target.

Technically, scaling only creates the illusion of an updated geometry and the question did say (other then scaling). So, I would say a better approach would be to reassign the geometry property of your mesh to a new geometry.
mesh.geometry = new THREE.BoxGeometry(newSize, newSize, newSize)
With this approach you can update any aspect of the geometry including width segments for example. This is especially useful when working with non box geometries like cylinders or spheres.
Here is a full working example using this approach:
let size = 10
let newSize = 20
// Create a blank geometry and make a mesh from it.
let geometry = new THREE.BoxGeometry()
let material = new THREE.MeshNormalMaterial()
let mesh = new THREE.Mesh(geometry, material)
// Adding this mesh to the scene won't display anything because ...
// the geometry has no parameters yet.
scene.add(mesh)
// Unless you intend to reuse your old geometry dispose of it...
// this will significantly reduce memory footprint.
mesh.geometry.dispose()
// Update the mesh geometry to a new geometry with whatever parameters you desire.
// You will now see these changes reflected in the scene.
mesh.geometry = new THREE.BoxGeometry(size, size, size)
// You can update the geometry as many times as you like.
// This can be done before or after adding the mesh to the scene.
mesh.geometry = new THREE.BoxGeometry(newSize, newSize, newSize)

How do I change the basic parameters of a Geometry in Three.js (for example, radius, number of vertices, etc.)

I create a tetrahedron of radius 3
// create a tetrahedron
var tetGeometry = new THREE.TetrahedronGeometry(3);
var tetMaterial = new THREE.MeshLambertMaterial(
{color: 0x20f020, transparent:true, opacity:0.6});
tet = new THREE.Mesh(tetGeometry, tetMaterial);
tet.name='tet';
tet.castShadow = true;
Later, I want the tetrahedron to grow:
// change hedron
scene.getObjectByName('tet').radius = control.hedronRadius;
That doesn't work.
// change vertices
scene.getObjectByName('tet').detail = control.hedronVertices;
That doesn't work either.
scene.getObjectByName('tet').verticesNeedUpdate;
And this doesn't help.
So how do I change the radius of a tetrahedron (or any Geometry) and how do I change the vertices.
In the documentation I see references to:
Geometry
.dynamic
.morph
.verticesNeedUpdate
.scale
And also references to bones and skeletons and skinned meshes used to animate geometries.
How do I change these aspects of Geometries in general?
What's the most reasonable, suggested way then to grow the radius of a Tetrahedron, or change the number of vertices show it becomes a different number polyhedron?

To change geometry you need to use:
morphTargets: true
I've prepared an example using a tetrahedron as you mention in jsfiddle.
Use sliders to change geometry.
To make some custom vertices and "fill" them by faces, you need to understand a lot of things from math, like; point, vector, etc.
I've done 2 simple flat objects, triangle and square in jsfiddle.
I hope that you'll easy understand how it works in general.

Threejs - Draw a transparent texture with MeshDepthMaterial

So I'm trying to have depth of field effect on some pixelart I made.
For that I need a texture with the depth information. So I render my texture on a plane using MeshDepthMaterial, but all I get is a grey rectangle, it completly ignores the alpha data in the texture (which is only 1 or 0, nothing inbetween).
Of course I'm using
depthMaterial.transparent = true;
depthMaterial.alphaTest = 0.5;
depthMaterial.needsUpdate = true; //just to be sure
Just for your interest this is my pixelart and how it is rendered: http://imgur.com/a/TLQOe

MeshDepthMaterial does not read the surface texture at all.
Instead you would need to either override the value of the 'depth' ShaderChunk to include UV's and your alpha-test-able texture, or add an extra ShaderMaterial to do the work yourself. Depending on the overall needs of your application, one approach would be better than the other. If no non-textured objects need to cast shadows, the former would be the simplest to maintain. If not, you'll need to do more work on managing which rendertargets get what and how.

Three.js outlines

Is it possible to have an black outline on my 3d models with three.js?
I would have graphics which looks like Borderlands 2. (toon shading + black outlines)

I'm sure I came in late. Let's hope this would solve someone's question later.
Here's the deal, you don't need to render everything twice, the overhead actually is not substantial, all you need to do is duplicate the mesh and set the duplicate mesh's material side to "backside". No double passes. You will be rendering two meshes instead, with most of the outline's geometry culled by WebGL's "backface culling".
Here's an example:
var scene = new THREE.Scene();
//Create main object
var mesh_geo = new THREE.BoxGeometry(1, 1, 1);
var mesh_mat = new THREE.MeshBasicMaterial({color : 0xff0000});
var mesh = new THREE.Mesh(mesh_geo, mesh_mat);
scene.add(mesh);
//Create outline object
var outline_geo = new THREE.BoxGeometry(1, 1, 1);
//Notice the second parameter of the material
var outline_mat = new THREE.MeshBasicMaterial({color : 0x00ff00, side: THREE.BackSide});
var outline = new THREE.Mesh(outline_geo, outline_mat);
//Scale the object up to have an outline (as discussed in previous answer)
outline.scale.multiplyScalar(1.5);
scene.add(outline);
For more details on backface culling, check out: http://en.wikipedia.org/wiki/Back-face_culling
The above approach works well if you want to add an outline to objects, without adding a toon shader, and thus losing "realism".
Toon shading by itself supports edge detection. They've developed the 'cel' shader in Borderlands to achieve this effect.
In cel shading devs can either use the object duplication method (done at the [low] pipeline level), or can use image processing filters for edge detection. This is the point at which performance tradeoff is compared between the two techniques.
More info on cel: http://en.wikipedia.org/wiki/Cel_shading
Cheers!

Yes it is possible but not in a simple out-of-the-box way. For toon shading there are even shaders included in /examples/js/ShaderToon.js
For the outlines I think the most commonly suggested method is to render in two passes. First pass renders the models in black, and slightly larger scale. Second pass is normal scale and with the toon shaders. This way you'll see the larger black models as an outline. It's not perfect but I don't think there's an easy way out. You might have more success searching for "three.js hidden line rendering", as, while different look, somewhat similar method is used to achieve that.

Its a old question but here is what i did.
I created a Outlined Cel-shader for my CG course. Unfortunately it takes 3 rendering passes. Im currently trying to figure out how to remove one pass.
Here's the idea:
1) Render NormalDepth image to texture.
In vertex shader you do what you normally do, position to screen space and normal to screen space.
In fragment shader you calculate the depth of the pixel and then create the normal color with the depth as the alpha value
float ndcDepth = (2.0 * gl_FragCoord.z - gl_DepthRange.near - gl_DepthRange.far) / (gl_DepthRange.far - gl_DepthRange.near);
float clipDepth = ndcDepth / gl_FragCoord.w;
2) Render the scene on to a texture with cel-shading. I changed the scene override material.
3)Make quad and render both textures on the quad and have a orto camera look at it. Cel-shaded texture is just renderd on quad but the normaldepth shaded on that you use some edge detection and then with that you know when the pixel needs to be black(edge).