Poly Frame surface node

Creates coordinate frame attributes for points and vertices.

All Parameters Example files

This node generates coordinate frame attributes for points and vertices based on a user selected frame-style. Computed frames consist of normal, tangent, and bitangent vectors; however, the user may choose to disable output of tangent and/or bitangent vectors. Computed vectors are normalized but are not necessarily orthogonal. You can choose to make the vectors orthogonal by turning on the Make frame orthogonal checkbox in the parameter editor.

The Texture Coordinates frame style requires texture coordinate attributes (either point or vertex attributes). Texture coordinates are taken from the current layer.

Parameters

Group

A subset of the source geometry for which attributes are to be computed.

Entity

The type of elements referenced in the Group field.

Style

First Edge

For each point, the normal vector is a smoothed point normal, the tangent vector is in the direction of the edge on which the point lies (specifically, the edge appearing first in the winding order), and the bitangent vector is orthogonal to the normal and tangent vectors. The following image shows tangent (red) and bitangent (yellow) vectors computed for the points of a triangle.

Two Edges

For each point, the normal vector is a smoothed point normal, the tangent vector is in the direction of the sum of the two edge vectors (where the edge vectors are the vector differences between the neighbouring points and the point for which the frame is being computed) on which the point lies, and the bitangent vector is orthogonal to the normal and tangent vectors. The following image shows tangent (red) and bitangent (yellow) vectors computed for the points of a triangle.

Primitive Centroid

For each point, the normal vector is a smoothed point normal, the tangent vector is in the direction of the vector difference of the point and the primitive centroid, and the bitangent is orthogonal to the normal and tangent vectors.

Texture Coordinates

For each vertex, the normal vector is the polygon’s surface normal, the tangent vector is in the direction of maximum increase of the u texture coordinate attribute, and the bitangent vector is in the direction of maximum increase of the v texture coordinate attribute.

Normal Name

The name of the normal attribute.

Tangent Name

The name of the tangent attribute.

Bitangent Name

The name of the bitangent attribute.

Make frame orthogonal

When enabled, enforces the constraint that the frame vectors be orthogonal. The tangent and bitangent vectors are adjusted to be orthogonal to each other and the normal.

Example files

TangentNormalMapExample

$HFS/houdini/help/examples/nodes/shop/ogl2_tangentnormalmap/TangentNormalMapExample.otl

Load | Launch

This example demonstrates how to use the Tangent Space Normal Map GLSL shader in conjunction with the PolyFrame SOP.

Usages in other examples

Example name Example for