Defect: V-Ray render hair width is 2x thinner than viewport in 5.2.1.40011 vs 5.1.5.37685

Problem

Description:

After upgrading from Ornatrix_Maya_2024_5_5.1.5.37685 to Ornatrix_Maya_2024_5_5.2.1.40011, hair/fur look identical in the Maya viewport, but the V-Ray render produces strands approximately 2x thinner than in the viewport, and 2x thinner than the same scene rendered with 5.1.5.37685.

In 5.1.5.37685 the viewport strand width matches the rendered strand width. In 5.2.1.40011 the viewport display is unchanged, so only the render output is affected. To match the previous render result, the width value in the width operator has to be multiplied by 2.

Here is video:

https://limewire.com/d/UARr1#fBXGhPmOYJ

Steps to Reproduce:

1. Create a polygon plane in a new scene. (in Ornatrix 5.1.5.37685, vray 7.20.04 or upper)

2. Add GuidesFromMesh, then HairFromGuides, then ChangeWidth with Width = 0.1.
3. Assign VRayHairNextMtl to the hair.
4. Open the exact same and render again with identical settings. (in Ornatrix 5.2.1.40011)
Result: in 5.1.5.37685 viewport and render match. In 5.2.1.40011 the render is ~2x thinner

6 September #41231
IvanKolev	Well, it turns out that V-Ray's internal translation of Ornatrix hair used to treat our "width" parameter as a "radius", effectively rendering the strands at double width. In Ornatrix 5.2.1 (as I mentioned in the "Ornatrix to USD Format" thread) the translation of Ornatrix hair to V-Ray is now handled by our own translator, which treats the width parameter correctly. I'm afraid existing scenes that used to render through V-Ray will have to double their width parameters when moving to 5.2.1. I attach some screenshots from my simple example scene, a plane of 10 units size with a checker texture with squares of 1 unit, and strands of width 0.5. VRayWidth-OrnatrixTranslator.jpg was rendered in 5.2.1 (with our translator), the strands there have widths of half a square, matching those displayed in the viewport, while in VRayWidth-VRayTranslator.jpg (rendered in 5.2.0 with V-Ray's internal translator) the strands have widths of one square. Attached Files: Ivan Kolev (Software Developer, EPHERE Inc.) Discord: ikolev Email: ivan.kolev at ephere com
6 September #41232
hitofffskiy	Thank you for the clear explanation - understood!

Title:	V-Ray render hair width is 2x thinner than viewport in 5.2.1.40011 vs 5.1.5.37685
Category:	Workflow
Status:	Open
Posted By:	hitofffskiy ( Roman A )
Date Created:	5 September 2026

Summary

Problem