Simplify shader (#29397)

src/renderers/shaders/ShaderLib/sprite.glsl.js

@@ -12,11 +12,9 @@ void main() {
 
 	#include <uv_vertex>
 
-	vec4 mvPosition = modelViewMatrix * vec4( 0.0, 0.0, 0.0, 1.0 );
+	vec4 mvPosition = modelViewMatrix[ 3 ];
 
-	vec2 scale;
-	scale.x = length( vec3( modelMatrix[ 0 ].x, modelMatrix[ 0 ].y, modelMatrix[ 0 ].z ) );
-	scale.y = length( vec3( modelMatrix[ 1 ].x, modelMatrix[ 1 ].y, modelMatrix[ 1 ].z ) );
+	vec2 scale = vec2( length( modelMatrix[ 0 ].xyz ), length( modelMatrix[ 1 ].xyz ) );
 
 	#ifndef USE_SIZEATTENUATION