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.
