Access camera position in gsplatCustomizeVS

Help & Support Gaussian Splatting
1

Is it possible to get the camera position when overriding the gsplatCustomize shader chunk?

This would be extremly useful to do effects based on splat distance to camera.

2

not automatically, but you can add any uniforms and pass what you need to those shaders. Similarly how parameters (lets say the center here) gets set:

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3

Yep that works. I thought there might be a better solution. I know there is a uniform view_position in the standard shader. Altough that one is in the fragment shader.

Follow up question:
The camera position is in world space. The center of modifyCenter however is in the gsplat model space.
Whats the best way to convert one space to the other?

EDIT: I’ve tried converting with matrix_model however it only gets defined later in the shader.

4

yep, for this you can simply add the uniform to your shader, and the engine will supply the value automatically.

GLSL

uniform vec3 view_position;

WGSL

uniform view_position: vec3f;
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5

I think in your case, maybe you need to convert the camera position to model space before setting it as uniform.

6

Alright I calculated the camera position in model space and supplied it to the shader:

this._worldToModelMatrix.copy(this.entity.getWorldTransform());
this._worldToModelMatrix.invert();
this._worldToModelMatrix.transformPoint(this.camera.getPosition(), this._transformedPoint);
this._cameraPositionArray[0] = this._transformedPoint.x;
this._cameraPositionArray[1] = this._transformedPoint.y;
this._cameraPositionArray[2] = this._transformedPoint.z;
this.entity.gsplat.material.setParameter('uCameraPosition', this._cameraPositionArray);

Works perfectly

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