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Anisotropy Rotation Test

Tags

extension, testing

Extensions Used

  • KHR_materials_anisotropy

Summary

This model tests rotational offsets for KHR_materials_anisotropy.

Operations

Screenshot

screenshot

Description

This model tests rotational offsets for KHR_materials_anisotropy. It has the following features:

  • Six of the meshes (2 on the bottom row, 2 in the middle, and 2 on the top row) are all "simple" anisotropy with material roughness extended horizontally along the mesh's TANGENT vectors.

  • One mesh in the lower-left marked "Tangents + Rotation" has a 30-degree clockwise tilt to the TANGENT vectors, and un-does this rotation using the anisotropyRotation parameter in radians equivalent to 30 degrees counter-clockwise. When the rotation is applied correctly, the anisotropy here should look the same as the neighboring meshes.

  • One mesh in the upper-left marked "Tangents + Texture" has the same 30-degree clockwise tilt to the TANGENT vectors, and un-does this rotation using the anisotropyTexture parameter with a 30-degree counter-clockwise tilt encoded in the texture. As before, when the rotation is applied correctly, the anisotropy here should look the same as the neighboring meshes.

  • One mesh in the lower-right marked "Tangents + Texture + Rotation" has again the same 30-degree clockwise tilt to the TANGENT vectors as the others. However this mesh uses a combination of 10 degrees from anisotropyTexture and 20 degrees (in radians) from anisotropyRotation, combining to create the 30-degree counter-clockwise tilt needed to make the anisotropy horizontal like the other meshes.

  • Finally, one mesh in the upper-right marked "Normal map of grooves" has no anisotropy applied at all. It has a (somewhat grainy) normal texture applied with a series of vertical grooves, intended to approximate the look of very coarse horizontal anisotropy. It will not look exactly the same as its neighbors, but a bright light source in the environment should still spread out horizontally like its neighbors.

IBL Example

IBL screenshot

With a full IBL reflection environment, the model should show horizontal stretching. It may appear similar to the screenshot above.

Incorrect Rotation Example

rotation failure screenshot

In the above image, the six "Basic Anisotropy" meshes are correct. But on the left side, both the texture-based rotation and JSON-based rotation are incorrect, and in the lower-right, the combination of both is also incorrect. These test meshes use a 30-degree clockwise slant in the tangent vectors that is intended to be undone by a 30-degree counter-clockwise rotation in the material. However in this image, a 60-degree clockwise rotation is visible on all three of these meshes, indicating that the material rotated the opposite way.

Legal

© 2023, Analytical Graphics, Inc.. CC BY 4.0 International

  • Ed Mackey for Everything

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