How to fit camera to model

[goldenratio]

Hi,
I am working gtlf viewer like app, where users can load different models. I would like the model to fit the camera. Something similar to this https://stackoverflow.com/questions/14614252/how-to-fit-camera-to-object

How can I achieve this with camera orbit control? Any help is appreciated.

[jnsmalm]

Hey,

First you need to calculate the bounds of the model.

const getMeshBounds = (mesh) => {
    let min = PIXI3D.Vec3.transformMat4(
      mesh.geometry.positions.min, mesh.worldTransform.array)
    let max = PIXI3D.Vec3.transformMat4(
      mesh.geometry.positions.max, mesh.worldTransform.array)
    for (let i = 0; i < 3; i++) {
      let temp = min[i]
      min[i] = Math.min(min[i], max[i])
      max[i] = Math.max(temp, max[i])
    }
    return { min, max }
  }

  const getModelBounds = (model) => {
    model.updateTransform()
    let modelBounds = getMeshBounds(model.meshes[0])
    for (let i = 1; i < model.meshes.length; i++) {
      let meshBounds = getMeshBounds(model.meshes[i])
      for (let j = 0; j < 3; j++) {
        modelBounds.min[j] =
          Math.min(modelBounds.min[j], meshBounds.min[j])
        modelBounds.max[j] =
          Math.max(modelBounds.max[j], meshBounds.max[j])
      }
    }
    return modelBounds
  }

The we need the function which uses the bounds and calculates the distance of the camera from the object.

const setDistanceToFitModel = (cameraControl, model) => {
    let bounds = getModelBounds(model)
    let aspect = window.innerWidth / window.innerHeight
    let min = bounds.min
    let max = bounds.max
    let height = Math.abs(min[1]) + Math.abs(max[1])
    let width = Math.abs(min[0]) + Math.abs(max[0])
    let depth = Math.abs(min[2]) + Math.abs(max[2])
    let fov = PIXI3D.Camera.main.fieldOfView

    cameraControl.distance = height / 2 / Math.tan(Math.PI * fov / 360)
    cameraControl.distance = Math.max(cameraControl.distance,
      width / aspect / 2 / Math.tan(Math.PI * fov / 360))
    cameraControl.distance += (max[2] + Math.abs(min[2])) / 2

    cameraControl.target.x = (max[0] + min[0]) / 2
    cameraControl.target.y = (max[1] + min[1]) / 2
    cameraControl.target.z = (max[2] + min[2]) / 2
  }

I have tested with a few models, and it seems to work.

[jnsmalm]

I realise that I should probably add a function to Pixi3D which calculates the bounds of a mesh/model.

[goldenratio]

yep, thanks! above code snippet works well.