apply UV2 Y-flip to Legacy and M3 renderers for OpenGL origin consistency

Author: Kruithne

src/js/3D/renderers/M2LegacyRendererGL.js

@@ -354,9 +354,9 @@ class M2LegacyRendererGL {
 			vertex_view.setFloat32(offset + 32, m2.uv[uv_idx], true);
 			vertex_view.setFloat32(offset + 36, m2.uv[uv_idx + 1], true);
 
-			// texcoord2
+			// texcoord2 (y-flipped for opengl bottom-left origin)
 			vertex_view.setFloat32(offset + 40, m2.uv2[uv_idx], true);
-			vertex_view.setFloat32(offset + 44, m2.uv2[uv_idx + 1], true);
+			vertex_view.setFloat32(offset + 44, 1 - m2.uv2[uv_idx + 1], true);
 		}
 
 		// map triangle indices

src/js/3D/renderers/M2RendererGL.js

@@ -525,7 +525,7 @@ class M2RendererGL {
 			vertex_view.setFloat32(offset + 32, m2.uv[uv_idx], true);
 			vertex_view.setFloat32(offset + 36, m2.uv[uv_idx + 1], true);
 
-			// texcoord2
+			// texcoord2 (y-flipped for opengl bottom-left origin)
 			vertex_view.setFloat32(offset + 40, m2.uv2[uv_idx], true);
 			vertex_view.setFloat32(offset + 44, 1 - m2.uv2[uv_idx + 1], true);
 		}

src/js/3D/renderers/M3RendererGL.js

@@ -124,9 +124,9 @@ class M3RendererGL {
 			vertex_view.setFloat32(offset + 32, m3.uv ? m3.uv[uv_idx] : 0, true);
 			vertex_view.setFloat32(offset + 36, m3.uv ? m3.uv[uv_idx + 1] : 0, true);
 
-			// texcoord2
+			// texcoord2 (y-flipped for opengl bottom-left origin)
 			vertex_view.setFloat32(offset + 40, m3.uv2 ? m3.uv2[uv_idx] : 0, true);
-			vertex_view.setFloat32(offset + 44, m3.uv2 ? m3.uv2[uv_idx + 1] : 0, true);
+			vertex_view.setFloat32(offset + 44, m3.uv2 ? 1 - m3.uv2[uv_idx + 1] : 0, true);
 		}
 
 		// create VAO