How can a mesh always appear the same size no matter where the camera is

giao123-cloud · March 28, 2023, 6:01am

how can a mesh always appear the same size no matter how camera move

giao123-cloud · March 28, 2023, 6:01am

like the gizmo, it always appear the same size

Cedric · March 28, 2023, 8:36am

It’s scaled with a factor corresponding to the distance to the camera.
In other words, the further away, the bigger.

BabylonJS/Babylon.js/blob/e363fcb251e7e1938aa073923590015b5f97a62f/packages/dev/core/src/Gizmos/gizmo.ts#L296


      
              this._rootMesh.position.subtractToRef(cameraPosition, TmpVectors.Vector3[0]);

              let scale = this.scaleRatio;

              if (activeCamera.mode == Camera.ORTHOGRAPHIC_CAMERA) {

                  if (activeCamera.orthoTop && activeCamera.orthoBottom) {

                      const orthoHeight = activeCamera.orthoTop - activeCamera.orthoBottom;

                      scale *= orthoHeight;

                  }

              } else {

                  const camForward = activeCamera.getScene().useRightHandedSystem ? Vector3.RightHandedForwardReadOnly : Vector3.LeftHandedForwardReadOnly;

                  const direction = activeCamera.getDirection(camForward);

                  scale *= Vector3.Dot(TmpVectors.Vector3[0], direction);

              }

              this._rootMesh.scaling.setAll(scale);

          

              // Account for handedness, similar to Matrix.decompose

              if (effectiveNode._getWorldMatrixDeterminant() < 0 && !Gizmo.PreserveScaling) {

                  this._rootMesh.scaling.y *= -1;

              }

          } else {

              this._rootMesh.scaling.setAll(this.scaleRatio);

          }

giao123-cloud · March 28, 2023, 9:21am

thanks for reply! I tried this in my code , but it didnot work and mesh become very big…

is there something wrong with my code?

Cedric · March 28, 2023, 12:03pm

Plase, create a playground so we can take a look.

sebavan · March 28, 2023, 3:26pm

Another trick is to use an orthographic camera instead of a perspective one.

giao123-cloud · March 29, 2023, 2:35am

thanks for your patient to look at this playground !

Cedric · March 29, 2023, 8:12am

Here is a quick example

giao123-cloud · March 29, 2023, 8:43am

thanks ! you really helped my work !