How do you remove/hide the end faces of the cylinder primitive?

mrLoganite · August 16, 2016, 9:19am

Hi,
Is it possible to remove the end faces of the cylinder primitive so that its hollow or will I need to create a model?

will · August 16, 2016, 9:38am

There’s no option in the API to remove the cylinder caps. However, you could just grab and modify the existing source to generate a cylinder:

github.com

playcanvas/engine/blob/master/src/scene/procedural.js#L615




               if (i > 1) {
                   indices.push(offset, offset + i - 1, offset + i);
               }
           }
       }
   }


   return {
       positions: positions,
       normals: normals,
       uvs: uvs,
       uvs1:uvs1,
       indices: indices
   };
};


/**
* @function
* @name pc.createCylinder
* @description Creates a procedural cylinder-shaped mesh.

This would mainly involve deleting generation of the cap triangles here:

github.com

playcanvas/engine/blob/master/src/scene/procedural.js#L437


bottom = new pc.Vec3(sinTheta * baseRadius, -height / 2.0, cosTheta * baseRadius);
top    = new pc.Vec3(sinTheta * peakRadius,  height / 2.0, cosTheta * peakRadius);
pos.lerp(bottom, top, i / heightSegments);
bottomToTop.sub2(top, bottom).normalize();
tangent = new pc.Vec3(cosTheta, 0.0, -sinTheta);
norm.cross(tangent, bottomToTop).normalize();


positions.push(pos.x, pos.y, pos.z);
normals.push(norm.x, norm.y, norm.z);
u = j / capSegments;
v = i / heightSegments;
uvs.push(u, v);


// Pack UV1 to 1st third
var _v = v;
v = u;
u = _v;
u /= 3;
u = u * primitiveUv1PaddingScale + primitiveUv1Padding;
v = v * primitiveUv1PaddingScale + primitiveUv1Padding;
uvs1.push(u, v);

But it might be quicker and easier to just open 3DS Max/Maya/Blender and create a tube.

mikefinch · August 16, 2016, 1:07pm

I think you can get access to buffers of model and change geometry there.

By the way, the easiest way to hide a face is custom shader.

Nice tutorial, which demonstrates how to hide part of model.