InstancedMesh: Tangents are not transformed by instance matrices

[gkjohnson]

Description

When adding batching shading I noticed that the tangent seemed to not be transformed by the instance matrix - is this a bug?

three.js/src/renderers/shaders/ShaderChunk/defaultnormal_vertex.glsl.js

Lines 25 to 35 in 0319a2a

	#ifdef USE_TANGENT
	vec3 transformedTangent = ( modelViewMatrix * vec4( objectTangent, 0.0 ) ).xyz;
	#ifdef FLIP_SIDED
	transformedTangent = - transformedTangent;
	#endif
	#endif

Reproduction steps

Issue found by looking at shader code.

Code

From defaultnormal_vertex.glsl.js:

#ifdef USE_TANGENT

	vec3 transformedTangent = ( modelViewMatrix * vec4( objectTangent, 0.0 ) ).xyz;

	#ifdef FLIP_SIDED

		transformedTangent = - transformedTangent;

	#endif

#endif

Live example

Issue found by looking at shader code.

Screenshots

No response

Version

dev

Device

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Browser

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OS

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[Mugen87]

is this a bug?

IMO, yes. Since the tangent is multiplied with modelViewMatrix, the additional transformations of instanceMatrix should be honored as well.