Octane Standalone Documentation

Perspective mapping takes the world space coordinates and divides the X and Y coordinates by the Z coordinate (Figure 1). The Transformation and Coordinate Space parameters can be used to orient the texture using this projection type.The Use Rest Attribute option keeps texture maps from distorting when the geometry is animated. Contrary to the projection type name, this projection type is not the most effective for setting up a traditional camera mapped project. An OSL Projection would be more effective. 

Figure 1: The Perspective projection node orienting a Checks texture

In figure 2, an OSL script was used with an OSL Projection node to project a procedural marble texture from the active camera view. 

Figure 2: Using the OSL Projection node for camera projection

The OSL script used for figure 2 is listed below:

// Camera projection onto 3D scene geometry

shader CameraMap_geo(

    output point uvw = 0

)

{

    // Transform shading point P from world space into camera space

    vector p = transform("camera", P);

    float fov;

    int res[2];

    // Dynamically retrieve the current camera's FOV and resolution aspect ratio

    getattribute("camera:fov", fov);

    getattribute("camera:resolution", res);

    // Map coordinates to 0-1 UV coordinate space, compensating for aspect ratio

    uvw[0] = 0.5 - 0.5 * p[0] / p[2] / tan(fov / 2);

    uvw[1] = 0.5 - 0.5 * p[1] / p[2] / tan(fov / 2) * res[0] / res[1];

}