ShaderMaterial preventing Instance Mesh setMatrixAt from updating

Questions
,
1

The SphereInstanceMeshOutline’s instances are stuck at 0,0,0 and aren’t updating at all. I think the shader is causing an interference?

// Outlines
const outlineThickness = 0.05;
const outlineGeo = new THREE.SphereGeometry( 0.5, 32, 16 );
const outlineMesh = new THREE.ShaderMaterial( {
	vertexShader: `
		void main( ) {
			vec3 newPosition = position + normal * ${outlineThickness};
			gl_Position = projectionMatrix * modelViewMatrix * vec4( newPosition, 1 );
		}
	`,
	fragmentShader: `
		void main( ) {
			gl_FragColor = vec4( 0.2, 0.2, 0.2, 1 );
		}
	`,
	side: THREE.BackSide
} );

SphereInstanceMeshOutline = new THREE.InstancedMesh( outlineGeo, outlineMesh, amount );
SphereInstanceMeshOutline.material.needsUpdate = true;

function updateInstance( dummy, index ) {
	dummy.updateMatrix( );
	SphereInstanceMeshOutline.setMatrixAt( index, object.matrix );
	
	SphereInstanceMeshOutline.instanceMatrix.needsUpdate = true;
}

When I try to replace the ShaderMaterial to a simple MeshStandardMaterial for testing purposes, the instances positions update normally

2

Your shader needs to use the instance’s matrix or all your instances will be at the same position, see the code here.

2 Likes
3

Added the multiplier instanceMatrix to the gl_Position:
gl_Position = projectionMatrix * modelViewMatrix * instanceMatrix * vec4( newPosition, 1 );

Works perfectly! Thank you very much!

1 Like