Class EXTPointParameters
- java.lang.Object
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- org.lwjgl.opengl.EXTPointParameters
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public class EXTPointParameters extends java.lang.Object
Native bindings to the EXT_point_parameters extension.This extension supports additional geometric characteristics of points. It can be used to render particles or tiny light sources, commonly referred as "Light points".
The raster brightness of a point is a function of the point area, point color, point transparency, and the response of the display's electron gun and phosphor. The point area and the point transparency are derived from the point size, currently provided with the
size
parameter ofPointSize
.The primary motivation is to allow the size of a point to be affected by distance attenuation. When distance attenuation has an effect, the final point size decreases as the distance of the point from the eye increases.
The secondary motivation is a mean to control the mapping from the point size to the raster point area and point transparency. This is done in order to increase the dynamic range of the raster brightness of points. In other words, the alpha component of a point may be decreased (and its transparency increased) as its area shrinks below a defined threshold.
This extension defines a derived point size to be closely related to point brightness. The brightness of a point is given by:
1 dist_atten(d) = ------------------- a + b * d + c * d^2 brightness(Pe) = Brightness * dist_atten(|Pe|)
where 'Pe' is the point in eye coordinates, and 'Brightness' is some initial value proportional to the square of the size provided with glPointSize. Here we simplify the raster brightness to be a function of the rasterized point area and point transparency.
brightness(Pe) brightness(Pe) >= Threshold_Area area(Pe) = Threshold_Area Otherwise factor(Pe) = brightness(Pe)/Threshold_Area alpha(Pe) = Alpha * factor(Pe)
where 'Alpha' comes with the point color (possibly modified by lighting).
'Threshold_Area' above is in area units. Thus, it is proportional to the square of the threshold provided by the programmer through this extension.
The new point size derivation method applies to all points, while the threshold applies to multisample points only.
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Field Summary
Fields Modifier and Type Field and Description static int
GL_DISTANCE_ATTENUATION_EXT
GL_POINT_FADE_THRESHOLD_SIZE_EXT
GL_POINT_SIZE_MAX_EXT
GL_POINT_SIZE_MIN_EXTAccepted by thepname
parameter of glPointParameterfvEXT, and thepname
of glGet.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method and Description static void
glPointParameterfEXT(int pname, float param)
static void
glPointParameterfvEXT(int pname, float[] params)
Array version of:PointParameterfvEXT
static void
glPointParameterfvEXT(int pname, java.nio.FloatBuffer params)
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Field Detail
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GL_POINT_SIZE_MIN_EXT, GL_POINT_SIZE_MAX_EXT, GL_POINT_FADE_THRESHOLD_SIZE_EXT, GL_DISTANCE_ATTENUATION_EXT
Accepted by thepname
parameter of glPointParameterfvEXT, and thepname
of glGet.
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Method Detail
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glPointParameterfEXT
public static void glPointParameterfEXT(int pname, float param)
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glPointParameterfvEXT
public static void glPointParameterfvEXT(int pname, java.nio.FloatBuffer params)
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glPointParameterfvEXT
public static void glPointParameterfvEXT(int pname, float[] params)
Array version of:PointParameterfvEXT
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