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lit.3Cg
Langue: en
Version: 354336 (ubuntu - 24/10/10)
Section: 3 (Bibliothèques de fonctions)
NAME
lit - computes lighting coefficients for ambient, diffuse, and specular lighting contributionsSYNOPSIS
float4 lit(float NdotL, float NdotH, float m);
half4 lit(half NdotL, half NdotH, half m);
fixed4 lit(fixed NdotL, fixed NdotH, fixed m);
PARAMETERS
- NdotL
- The dot product of a normalized surface normal and a normalized light vector.
- NdotH
- The dot product of a normalized surface normal and a normalized half-angle vector (for Blinn-style specular) where the half-angle vector is the sum of the normalized view vector and normalized light vector. Alternatively, the dot product of a normlized light vector and a normalized view vector reflected by a normalized surface normal could be used (for Phong-style specular).
- m
- A specular exponent, typically described as a measure of shininess. The larger the exponent, the shinier the specular highlight, the smaller the exponent, the duller the specular highlight.
DESCRIPTION
The lit function is a helper function useful to compute lighting coefficients for ambient, diffuse, and specular lighting contributions. The function efficiently maps to a native instruction for most GPUs.lit returns a 4-component vector arranged as follows:
- x
- The ambient coefficient that is always 1.0.
- y
- The diffuse coefficient that is zero if NdotL is less than zero, and NdotL otherwise.
- z
- The specular coefficient that is zero if either NdotL or NdotH are less than zero, and otherwise NdotH raised to the power m.
- w
- Always 1.0.
REFERENCE IMPLEMENTATION
lit accepting <float> parameters could be implemented this way:float4 lit(float NdotL, float NdotH, float m) { float specular = (NdotL > 0) ? pow(max(0.0, NdotH), m); return float4(1.0, max(0.0, NdotL), specular, 1.0); }
PROFILE SUPPORT
lit is supported in all profiles.SEE ALSO
dot, max, normalize, powContenus ©2006-2024 Benjamin Poulain
Design ©2006-2024 Maxime Vantorre