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// Camera projector osl by Vicente Lucendo - https://vlucendo.com
shader CameraProjector
[[
string label = "Perspective Camera Projector",
string help = "<h3>Perspective Camera Projector</h3> Node to project from a perspective camera",
string version = "0.1"
]]
(
// inputs
int projectBackface = 0 [[ string widget = "checkBox" ]],
point position = point(0, 0, 10),
vector rotation = vector(0, 0, 0),
float width = 1280 [[ float min = 1, float max = 999999 ]],
float height = 720 [[ float min = 1, float max = 999999 ]],
float pixelAspect = 1.0 [[ float min = 0.0001, int max = 999999 ]],
float focalLength = 50.0 [[ float min = 1, float max = 180 ]],
float aperture = 41.4214 [[ float min = 1, float max = 180 ]],
// output
output point uvw = 0
)
{
point meshPosition = P;
vector offset = meshPosition - position;
vector dir = normalize(offset);
// don't project backfaces
if (projectBackface == 0 && dot(transform("world", N), dir) > 0.0) return;
// calculate the camera rotation as a matrix4. we assume rotation is in default order
vector rotRad = radians(rotation);
float a = cos(rotRad.x);
float b = sin(rotRad.x);
float c = cos(rotRad.y);
float d = sin(rotRad.y);
float e = cos(rotRad.z);
float f = sin(rotRad.z);
float ae = a * e;
float af = a * f;
float be = b * e;
float bf = b * f;
// create inverted matrix directly
matrix rot = matrix (
c * e, c * f, - d, 0,
be * d - af, bf * d + ae, b * c, 0,
ae * d + bf, af * d - be, a * c, 0,
0, 0, 0, 1
);
// position in camera space
point pos = transform(rot, offset);
// houdini's camera fov
float apy = (height * aperture) / (width * pixelAspect);
float fov = 2 * atan((apy / 2) / focalLength);
// project the point
float ff = 1.0 / tan(fov / 2);
float aspect = width / height;
ff /= pos.z;
pos.x *= ff / aspect;
pos.y *= ff;
// change range from -1..1 to 0..1
pos.x = 1.0 - (pos.x * 0.5 + 0.5);
pos.y = 1.0 - (pos.y * 0.5 + 0.5);
// dont project off limits
if (pos.x < 0.0 || pos.x > 1.0 || pos.y < 0.0 || pos.y > 1.0) return;
uvw.x = pos.x;
uvw.y = pos.y;
}
