Houdini 20.0 Nodes VOP nodes

Karma Light Projection VOP node

You can use this utility node in a light filter network to get the UV coordinates of the “current ray” in the light’s projection space.

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Since 19.5

Overview

You can combine this with a 2D function (for example, MtlX Fractal3D) and connect it to a light filter node, such as to a Gel light filter node’s Intensity input, to modify the light output across its field of view according to the function. For example, you could use 2D noise to generate fake caustics.

Tips and notes

  • If you just want to project the light through a texture, just use the Gobo light filter which is dedicated to that purpose.

  • Use the parameters to control the size and positioning of the projected texture space.

  • Use Material X VOP nodes to calculate values, noise, etc. based on this node’s output.

  • This node currently does not work with the Karma XPU renderer.

Parameters

Use Cone Angle

Match the projection to the light’s Cone angle. If this is off (or the light’s cone angle is greater than or equal to 90 degrees), the projection will use a cone angle of 45 degrees.

U Scale

Scale the horizontal field of view of the projection by this amount.

V Scale

Scale the vertical field of view of the projection by this amount.

U Offset

Offset the projection by this amount in the horizontal direction.

V Offset

Offset the projection by this amount in the vertical direction.

Outputs

uv

(vector2) The UV coordinates of the “current ray” in the light’s projected 2D space.

z

(float) The distance between the light and the point on the surface being shaded.

valid

(int) This is 1 if the hit point is in front of the light source, or 0 if it’s behind the light source.

See also

VOP nodes