- Name
-
gl.Map -- define a one- or two-dimensional evaluator
- Synopsis
-
gl.Map(target, u1, u2, pointsArray)
gl.Map(target, u1, u2, v1, v2, pointsArray)
- Function
-
Evaluators provide a way to use polynomial or rational polynomial mapping to produce vertices, normals,
texture coordinates, and colors. The values produced by an evaluator are sent to further stages of GL
processing just as if they had been presented using gl.Vertex(), gl.Normal(),
gl.TexCoord(), and gl.Color() commands, except that the generated
values do not update the current normal, texture coordinates, or color.
All polynomial or rational polynomial splines of any degree (up to the maximum degree supported by the GL
implementation) can be described using evaluators. These include almost all splines used in computer graphics:
B-splines, Bezier curves, Hermite splines, and so on.
gl.Map()
is used to define the basis and to specify what kind of values are produced.
Once defined, a map can be enabled and disabled by calling gl.Enable() and gl.Disable()
with the map name, one of the nine predefined values for target described below. gl.EvalCoord()
evaluates the one-dimensional maps that are enabled. When gl.EvalCoord() presents a value u or
values u and v, the Bernstein functions are evaluated using u^ and v^ , where
| u^ = (u - u1) / (u2 - u1)
v^ = (v - v1) / (v2 - v1)
|
target
is a symbolic constant that indicates what kind of control points are provided in pointsArray
, and what output is generated
when the map is evaluated. In one-dimensional mode it can assume one of the following nine predefined values:
#GL_MAP1_VERTEX_3
-
Each control point is three floating-point values representing x, y, and z. Internal gl.Vertex() commands are generated when the map is evaluated.
#GL_MAP1_VERTEX_4
-
Each control point is four floating-point values representing x, y, z, and w. Internal gl.Vertex() commands are generated when the map is evaluated.
#GL_MAP1_INDEX
-
Each control point is a single floating-point value representing a color index. Internal gl.Index() commands are generated when the map is
evaluated but the current index is not updated with the value of these gl.Index() commands.
#GL_MAP1_COLOR_4
-
Each control point is four floating-point values representing red, green, blue, and alpha. Internal gl.Color() commands are generated when the
map is evaluated but the current color is not updated with the value of these gl.Color() commands.
#GL_MAP1_NORMAL
-
Each control point is three floating-point values representing the x, y, and z components of a normal vector. Internal gl.Normal() commands are
generated when the map is evaluated but the current normal is not updated with the value of these gl.Normal() commands.
#GL_MAP1_TEXTURE_COORD_1
-
Each control point is a single floating-point value representing the s texture coordinate. Internal gl.TexCoord() commands are generated when the
map is evaluated but the current texture coordinates are not updated with the value of these gl.TexCoord() commands.
#GL_MAP1_TEXTURE_COORD_2
-
Each control point is two floating-point values representing the s and t texture coordinates. Internal gl.TexCoord() commands are generated when
the map is evaluated but the current texture coordinates are not updated with the value of these gl.TexCoord() commands.
#GL_MAP1_TEXTURE_COORD_3
-
Each control point is three floating-point values representing the s, t, and r texture coordinates. Internal gl.TexCoord() commands are generated
when the map is evaluated but the current texture coordinates are not updated with the value of these gl.TexCoord() commands.
#GL_MAP1_TEXTURE_COORD_4
-
Each control point is four floating-point values representing the s, t, r, and q texture coordinates. Internal gl.TexCoord() commands are generated
when the map is evaluated but the current texture coordinates are not updated with the value of these gl.TexCoord() commands.
In two-dimensional mode the following predefined constants are supported:
#GL_MAP2_VERTEX_3
-
Each control point is three floating-point values representing x, y, and z. Internal gl.Vertex() commands are generated when the map is evaluated.
#GL_MAP2_VERTEX_4
-
Each control point is four floating-point values representing x, y, z, and w. Internal gl.Vertex() commands are generated when the map is evaluated.
#GL_MAP2_INDEX
-
Each control point is a single floating-point value representing a color index. Internal gl.Index() commands are generated when the map
is evaluated but the current index is not updated with the value of these gl.Index() commands.
#GL_MAP2_COLOR_4
-
Each control point is four floating-point values representing red, green, blue, and alpha. Internal gl.Color() commands are generated when
the map is evaluated but the current color is not updated with the value of these gl.Color() commands.
#GL_MAP2_NORMAL
-
Each control point is three floating-point values representing the x, y, and z components of a normal vector. Internal gl.Normal() commands
are generated when the map is evaluated but the current normal is not updated with the value of these gl.Normal() commands.
#GL_MAP2_TEXTURE_COORD_1
-
Each control point is a single floating-point value representing the s texture coordinate. Internal gl.TexCoord() commands are generated when
the map is evaluated but the current texture coordinates are not updated with the value of these gl.TexCoord() commands.
#GL_MAP2_TEXTURE_COORD_2
-
Each control point is two floating-point values representing the s and t texture coordinates. Internal gl.TexCoord() commands are generated when
the map is evaluated but the current texture coordinates are not updated with the value of these gl.TexCoord() commands.
#GL_MAP2_TEXTURE_COORD_3
-
Each control point is three floating-point values representing the s, t, and r texture coordinates. Internal gl.TexCoord() commands are generated
when the map is evaluated but the current texture coordinates are not updated with the value of these gl.TexCoord() commands.
#GL_MAP2_TEXTURE_COORD_4
-
Each control point is four floating-point values representing the s, t, r, and q texture coordinates. Internal gl.TexCoord() commands are generated
when the map is evaluated but the current texture coordinates are not updated with the value of these gl.TexCoord() commands.
Initially, #GL_AUTO_NORMAL
is enabled. If #GL_AUTO_NORMAL
is enabled, normal vectors are generated when either #GL_MAP2_VERTEX_3
or #GL_MAP2_VERTEX_4
is used to generate vertices.
Please consult an OpenGL reference manual for more information.
- Inputs
-
- target
- specifies the kind of values that are generated by the evaluator (see above)
- u1
- specify a linear mapping of u, as presented to gl.EvalCoord(), to u^ , the variable that is evaluated by the equations specified by this command
- u2
- specify a linear mapping of u, as presented to gl.EvalCoord(), to u^ , the variable that is evaluated by the equations specified by this command
- v1
- specify a linear mapping of v, as presented to gl.EvalCoord(), to v^ , one of the two variables that are evaluated by the equations specified by this command
- v2
- specify a linear mapping of v, as presented to gl.EvalCoord(), to v^ , one of the two variables that are evaluated by the equations specified by this command
- pointsArray
- specifies a table containing a number of control points (see above)
- Errors
-
#GL_INVALID_ENUM
is generated if target
is not an accepted value.
#GL_INVALID_VALUE
is generated if u1
is equal to u2
, or if v1
is equal to v2
.
#GL_INVALID_OPERATION
is generated if gl.Map()
is executed between the execution of gl.Begin() and the corresponding execution of gl.End().
- Associated gets
-
gl.GetMap()
gl.Get() with argument #GL_MAX_EVAL_ORDER
gl.IsEnabled() with argument #GL_MAP1_VERTEX_3
gl.IsEnabled() with argument #GL_MAP1_VERTEX_4
gl.IsEnabled() with argument #GL_MAP1_INDEX
gl.IsEnabled() with argument #GL_MAP1_COLOR_4
gl.IsEnabled() with argument #GL_MAP1_NORMAL
gl.IsEnabled() with argument #GL_MAP1_TEXTURE_COORD_1
gl.IsEnabled() with argument #GL_MAP1_TEXTURE_COORD_2
gl.IsEnabled() with argument #GL_MAP1_TEXTURE_COORD_3
gl.IsEnabled() with argument #GL_MAP1_TEXTURE_COORD_4
gl.IsEnabled() with argument #GL_MAP2_VERTEX_3
gl.IsEnabled() with argument #GL_MAP2_VERTEX_4
gl.IsEnabled() with argument #GL_MAP2_INDEX
gl.IsEnabled() with argument #GL_MAP2_COLOR_4
gl.IsEnabled() with argument #GL_MAP2_NORMAL
gl.IsEnabled() with argument #GL_MAP2_TEXTURE_COORD_1
gl.IsEnabled() with argument #GL_MAP2_TEXTURE_COORD_2
gl.IsEnabled() with argument #GL_MAP2_TEXTURE_COORD_3
gl.IsEnabled() with argument #GL_MAP2_TEXTURE_COORD_4